Deborah Kay Harris, Administratrix v. CSX Transportation

IN THE SUPREME COURT OF APPEALS OF WEST VIRGINIA

September 2013 Term FILED
November 13, 2013
_____________ released at 3:00 p.m.
RORY L. PERRY II, CLERK
SUPREME COURT OF APPEALS
No. 12-1135 OF WEST VIRGINIA

_____________

DEBORAH KAY HARRIS, ADMINISTRATRIX OF THE ESTATE OF

RONALD K. HARRIS, DECEASED,

Plaintiff Below, Petitioner

V.

CSX TRANSPORTATION, INC.,
Defendant Below, Respondent

Appeal from the Circuit Court of Marshall County

Honorable David W. Hummel, Judge

Civil Action No. 08-C-171M(H)

REVERSED AND REMANDED

Submitted: October 15, 2013

Filed: November 13, 2013

R. Dean Hartley James W. Turner
Julie R. Magers Steptoe & Johnson
J. Michael Prascik Huntington, West Virginia
Hartley & O’Brien, P.L.L.C. Andrew E. Tauber
Wheeling, West Virginia Brian J. Wong
Attorneys for Petitioner Mayer Brown LLP
Washington, District of Columbia
Attorneys for Respondent

JUSTICE DAVIS delivered the Opinion of the Court.

CHIEF JUSTICE BENJAMIN concurs and reserves the right to file a concurring
opinion.
JUSTICE LOUGHRY dissents and reserves the right to file a dissenting opinion.

SYLLABUS BY THE COURT

1. When a circuit court excludes expert testimony as unreliable under the

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125 L. Ed. 2d

469 (1993), and Wilt v. Buracker, 191 W. Va. 39, 443 S.E.2d 196 (1993), gatekeeper

analysis, we will review the circuit court’s method of conducting the analysis de novo.

2. When a trial court is called upon to determine the admissibility of

scientific expert testimony, in deciding the “reliability” prong of admissibility the focus of

the trial court’s inquiry is limited to determining whether the expert employed a methodology

that is recognized in the scientific community for rendering an opinion on the subject under

consideration. If the methodology is recognized in the scientific community, the court should

then determine whether the expert correctly applied the methodology to render his or her

opinion. If these two factors are satisfied, and the testimony has been found to be relevant,

and the expert is qualified, the expert may testify at trial.

ii
Davis, Justice:

Deborah Kay Harris, administratrix of the Estate of Ronald K. Harris

(“Petitioner”), appeals an order of the Circuit Court of Marshall County granting summary

judgment in favor of CSX Transportation, Inc. (“CSX”). The circuit court granted summary

judgment after ruling that Petitioner was precluded from calling her three expert witnesses

at trial. The dispositive issue presented by the Petitioner in this appeal is whether the circuit

court committed error in finding the scientific testimony of Petitioner’s three expert

witnesses was not reliable.1 After a careful review of the briefs, the record submitted on

appeal and listening to the arguments of the parties, we reverse and remand this case.

I.

FACTUAL AND PROCEDURAL HISTORY

This action was originally filed by Ronald K. Harris under the Federal

Employers’ Liability Act2 and the Locomotive Inspection Act3 against his employer, CSX.4

The complaint alleged that Mr. Harris’ exposure to diesel exhaust fumes while employed by

1
The Petitioner set out three issues as assignments of error. However, we only
need to address the issue of the reliability of the testimony of Petitioner’s experts to resolve
this case.
2
See 45 U.S.C. §51 et seq. (1939).
3
See 49 U.S.C. § 0701 et seq. (1994).
4
The record submitted on appeal did not include the complaint.

1

CSX caused him to develop a type of cancer called multiple myeloma. While the case was

pending, Mr. Harris died as a result of the cancer. Petitioner, Mr. Harris’ wife and

administratrix of his estate, was substituted as the plaintiff. Petitioner amended the

complaint to allege that Mr. Harris’ death resulted from his exposure to diesel exhaust

fumes.5

When the parties concluded expert witness discovery, CSX filed a motion to

exclude the testimony of Petitioner’s three expert witnesses because their methodology was

not reliable. At the request of CSX, the trial court held an evidentiary hearing regarding the

admissibility of Petitioner’s expert witnesses’ testimony. The evidentiary hearing lasted two

days. During the hearing, Petitioner called her three experts, Dr. Peter Infante, Ph.D.; Dr.

Lawrence Goldstein, Ph.D.; and Dr. Brian Durie, M.D. CSX called two expert witnesses:

Dr. Peter Shields, M.D. and Dr. Laura Green, Ph.D. These evidentiary hearings in West

Virginia are commonly referred to as “Daubert/Wilt” hearings.

At the conclusion of the two-day evidentiary hearing, the circuit court entered

three orders excluding Petitioner’s experts’ testimony. The circuit court entered findings of

fact which, in essence, determined that Petitioner failed to prove to the court that diesel

exhaust exposure causes multiple myeloma. As a result of not having an expert, Petitioner

5
The amended complaint was not made part of the record on appeal.

2

agreed with CSX to jointly move for summary judgment in CSX’s favor so that Petitioner

could appeal the adverse expert witness rulings. The circuit court entered an order granting

summary judgment. This appeal followed.

II.

STANDARD OF REVIEW

In this proceeding, the circuit court granted summary judgment in favor of CSX

after excluding the testimony of Petitioner’s expert witnesses. We stated in Syllabus point

1 of Painter v. Peavy, 192 W. Va. 189, 451 S.E.2d 755 (1994), that “[a] circuit court’s entry

of summary judgment is reviewed de novo.” The parties agree. Without expert testimony

by the Petitioner, summary judgment is appropriate. Consequently, the dispositive ruling in

this case is not the summary judgment order. It is the orders precluding Petitioner’s three

experts from testifying. If those orders fail, summary judgment is not appropriate.

As a general matter, we have long held that “[t]he admissibility of testimony

by an expert witness is a matter within the sound discretion of the trial court, and the trial

court’s decision will not be reversed unless it is clearly wrong.” Syl. pt. 6, Helmick v.

Potomac Edison Co., 185 W. Va. 269, 406 S.E.2d 700 (1991). However, we have indicated,

and so hold, that “when a circuit court excludes expert testimony as unreliable under the

[Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125

3

L. Ed. 2d 469 (1993); and Wilt v. Buracker, 191 W. Va. 39, 443 S.E.2d 196 (1993),]

gatekeeper analysis, we will review the circuit court’s method of conducting the analysis de

novo.” San Francisco v. Wendy’s Int’l, Inc., 221 W. Va. 734, 740, 656 S.E.2d 485, 491

(2007) (citations omitted).

With these standards in mind, we turn to the issues presented by this appeal.

III.

DISCUSSION

In order to adequately address the dispositive issue in this case and give

guidance to trial judges in future cases similar to the instant matter, we have outlined our

discussion as follows: (1) general principles of Rule 702; (2) the nature of multiple myeloma;

(3) epidemiological methodology; (4) toxicological methodology; (5) weight of the evidence

methodology; (6) Bradford Hill methodology; (7) qualification, methodology and opinion of

the expert witnesses; and (8) the circuit court’s orders excluding the testimony of Petitioner’s

experts.

A. General Principles of Rule 702

Rule 702 of the West Virginia Rules of Evidence provides in full that, “[i]f

scientific, technical, or other specialized knowledge will assist the trier of fact to understand

4

the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge,

skill, experience, training, or education may testify thereto in the form of an opinion or

otherwise.” “Rule 702 reflects an attempt to liberalize the rules governing the admissibility

of expert testimony.” Weisgram v. Marley Co., 169 F. 3d 514, 523 (8th Cir. 1999). What

this means is that “[t]he rule ‘is one of admissibility rather than exclusion.’” In re Flood

Litig. Coal River Watershed, 222 W. Va. 574, 581, 668 S.E.2d 203, 210 (2008) (quoting

Arcoren v. United States, 929 F.2d 1235, 1239 (8th Cir. 1991). “Disputes as to the strength

of an expert’s credentials, mere differences in the methodology, or lack of textual authority

for the opinion go to weight and not to the admissibility of their [sic] testimony.” Gentry v.

Mangum, 195 W. Va. 512, 527, 466 S.E.2d 171, 186 (1995) (citation omitted).

The decisions of this Court have “explained that circuit courts must conduct

a two-part inquiry under Rule 702 and ask: (1) is the witness [qualified as] an expert; and,

if so, (2) is the expert’s testimony relevant and reliable?” San Francisco v. Wendy’s Int’l,

Inc., 221 W. Va. at 741, 656 S.E.2d at 492 (citations omitted). See also Robin Jean Davis,

Admitting Expert Testimony in Federal Courts and Its Impact on West Virginia

Jurisprudence, 104 W. Va. L. Rev. 485, 513 (2002) (“Trial courts are required to assess

scientific expert testimony for relevancy and reliability.”). In Syllabus point 5 of Gentry we

set out the steps that a trial court should take to determine if an expert is qualified to render

an opinion under Rule 702:

5

 In determining who is an expert, a circuit court should
conduct a two step inquiry. First, a circuit court must determine
whether the proposed expert (a) meets the minimal educational
or experiential qualifications (b) in a field that is relevant to the
subject under investigation (c) which will assist the trier of fact.
Second, a circuit court must determine that the expert’s area of
expertise covers the particular opinion as to which the expert
seeks to testify.

195 W. Va. 512, 466 S.E.2d 171.

The general standard for determining whether an expert’s scientific opinion is

relevant and reliable was set out in Syllabus point 2 of Wilt v. Buracker, 191 W. Va. 39, 443

S.E.2d 196:

In analyzing the admissibility of expert testimony under
Rule 702 of the West Virginia Rules of Evidence, the trial
court’s initial inquiry must consider whether the testimony is
based on an assertion or inference derived from the scientific
methodology. Moreover, the testimony must be relevant to a
fact at issue. Further assessment should then be made in regard
to the expert testimony’s reliability by considering its underlying
scientific methodology and reasoning. This includes an
assessment of (a) whether the scientific theory and its
conclusion can be and have been tested; (b) whether the
scientific theory has been subjected to peer review and
publication; (c) whether the scientific theory’s actual or
potential rate of error is known; and (d) whether the scientific
theory is generally accepted within the scientific community.

As is illustrated later in this opinion, the trial court’s decision to exclude

Petitioner’s three experts resulted from its determination that the scientific opinions of all

6

three of Petitioner’s experts were not reliable. The circuit court’s ruling shows a

misunderstanding of the meaning of “reliable” under West Virginia jurisprudence. We

previously have noted the contours of the meaning of “reliable’” as follows:

The assessment of whether scientifically-based expert
testimony is “reliable,” as that term is used in [Daubert v.
Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct.
2786, 125 L. Ed. 2d 469 (1993), and Wilt v. Buracker, 191
W. Va. 39, 443 S.E.2d 196 (1993)], does not mean an
assessment of whether the testimony is persuasive, convincing,
or well-founded. Rather, assessing “reliability” is a shorthand
term of art for assessing whether the testimony is to a reasonable
degree based on the use of knowledge and procedures that have
been arrived at using the methods of science—rather than being
based on irrational and intuitive feelings, guesses, or
speculation. If the former is the case, then the jury may (or may
not, in its sole discretion) “rely upon” the testimony.

In re Flood Litig., 222 W. Va. at 582 n.5, 668 S.E.2d at 211 n.5.

In Gentry, Justice Cleckley made the following relevant observation:

Under Daubert/Wilt, the circuit court conducts an inquiry
into the validity of the underlying science, looking at the
soundness of the principles or theories and the reliability of the
process or method as applied in the case. The problem is not to
decide whether the proffered evidence is right, but whether the
science is valid enough to be reliable.

Gentry, 195 W. Va. at 523, 466 S.E.2d at 182 (emphasis in original). It is noteworthy that

Justice Cleckley felt it was important to italicize the quoted second sentence: “The problem

is not to decide whether the proffered evidence is right, but whether the science is valid

enough to be reliable.” Id. As will be shown later in this opinion, the circuit court

7

misapplied this Court’s opinion in Gentry. That is, the circuit court decided the opinions

from Petitioner’s three experts were wrong. Under Gentry, right or wrong is not an issue of

the admissibility of scientific evidence. The circuit court made right or wrong a central test

for the admission of scientific evidence. In doing so, the circuit court removed from the jury

its exclusive role of deciding which expert opinion to believe.

Rule 702 and the decisions of this Court clearly state that it is of no moment

that the opinions of the parties’ experts reach different conclusions on all dispositive issues.

This is to be expected. Our legal system is adversarial, not cordial. As a result of the

adversarial essence of our legal system, we rely upon the jury to make the ultimate

determination as to which expert is right and which expert is wrong. To place the decision

in the hands of trial judges denies litigants their constitutional right to a jury trial.

The decision in State ex rel. Wiseman v. Henning, 212 W. Va. 128, 569 S.E.2d

204 (2002), illustrates this Court’s hostility to stripping litigants of the right to have a jury

decide if an expert is right or wrong. The plaintiff in Wiseman was injured in an automobile

accident and later developed multiple myeloma. The plaintiff filed a negligence action

against the truck driver and truck owner, alleging that his multiple myeloma resulted from

8

a rib cage injury he suffered in the traffic collision with the truck driver.6 The circuit court

granted defendants’ motion in limine to exclude testimony of the plaintiff’s expert witness

on causation. The plaintiff filed a petition for a writ of prohibition with this Court seeking

to prevent enforcement of the trial court’s order. This Court granted the writ after concluding

that plaintiff’s expert’s proffered opinion was sufficiently reliable to be admissible. The

opinion in Wiseman addressed the issue as follows:

Examining the record in the instant case, we believe that
the circuit court exceeded its authority in its decision to exclude
the testimony of Dr. Hussein. The record reflects that Dr.
Hussein was a member of several specialized cancer research
societies, and had substantial interaction with other cancer
specialists. He was a specialist in cancers such as that suffered
by Mr. Wiseman, and was director of the Myeloma Program at
the Cleveland Clinic. Dr. Hussein’s proffered opinion that
multiple myeloma can result from a trauma was based upon: his
extensive treatment of Mr. Wiseman; his treatment of five other
patients at the Cleveland Clinic who had trauma-induced
myelomas; his study of the physiological process of tissue injury
causing chronic inflammation and overstimulation of cells,
which triggers the growth of cancerous cells; his interaction
with other specialists who also believe that trauma can trigger
the occurrence of myeloma; and the handful of published studies
by other cancer centers that have identified local tissue injury,
including a bone fracture, as a risk factor for causing multiple
myeloma.

We recognize that Dr. Hussein’s opinion is novel and
unorthodox, and may not have yet received, as the circuit court
found, “general acceptance in the scientific community.”
However, the Rules of Evidence do not require that a scientific
opinion be “generally accepted,” because such a requirement is

6
A loss of consortium claim was also brought by the plaintiff’s wife.

9

 at odds with the liberal thrust of the . . . Rules and their general
approach of relaxing the traditional barriers to opinion
testimony. The record suggests a substantial degree of
reliability underlying the formation of Dr. Hussein’s opinion.
Accordingly, we find that the circuit court erred in excluding his
testimony. . . . The proffered opinion is valid enough to be
reliable; whether the proffered evidence is right is a question for
the finder of fact.

Wiseman, 212 W. Va. at 133-34, 569 S.E.2d at 209-10 (internal quotations and citations

omitted; emphasis added).7 See also Ruiz-Troche v. Pepsi Cola of Puerto Rico Bottling Co.,

161 F.3d 77, 85 (1st Cir. 1998) (“Daubert does not require that a party who proffers expert

testimony carry the burden of proving to the judge that the expert’s assessment of the

situation is correct.”).

B. The Nature of Multiple Myeloma

In the case sub judice, Mr. Harris was diagnosed with having multiple

myeloma. He died from this disease. This disease has been described as follows:

“[M]ultiple myeloma is a cancer of the plasma cell, a cell which
arises in bone marrow and is an important part of the immune
system as it provides antibodies which help fight infection and
other diseases. If a plasma cell becomes malignant, it is called
a myeloma cell. An individual with myeloma has an abnormal
build-up of myeloma cells in the bone marrow with
displacement of normal marrow and which results in tumors that
involve and destroy surrounding bone.

7
This opinion will conclude the discussion of the legal principles of
admissibility of expert testimony in the context of the circuit court’s ruling in Section III G,
infra.

10

World City Found., Inc. v. Sacchetti, No. 114829/03, 2008 WL 344131, at*4 (N.Y. Sup. Ct.

Jan. 28, 2008). Specifically, “‘[m]ultiple myeloma’ refers to the presence of numerous

myelomas in various bones of the body.” Hawaii Med. Serv. Ass’n v. Adams, 209 P.3d 1260,

1263 n.4 (Haw. Ct. App. 2009). During the underlying proceedings herein, multiple

Myeloma was described by the expert for CSX, Dr. Shields, as follows:

So multiple myeloma is a cancer of one of the types of
blood cells. It’s actually in plasma cells, which is a type of B
cell, and the plasma cells are responsible for making antibodies
to fight infection. And what happens is that if you get a
myeloma, all the plasma cells or one type of plasma cell,
actually started growing uncontrollably and pushing everything
out . . .

....

. . . So plasma cell is one of the – is one of the blood cells
that’s part of the immune system that makes those antibodies
fight, you know, the common cold, pneumonia, that sort of
thing.

And so what happens is as those cells grow, those plasma
cells, and become plasmacytomas; where they like live . . . in
the bones. And so that’s the myeloma. So the myeloma part is
the bones, and multiple is you get multiple bone lesions. And as
it’s – as it’s living in the bones, it starts crowding up the bone
marrow, and you start having other bood count effects. You
have immune system problems and that sort of thing.

See also Toney v. State, 961 N.E.2d 57, 60 (Ind. Ct. App. 2012) (“[M]ultiple myeloma [is]

a cancer of the plasma cells in bone marrow.”); Williams v. Superior Uniform Grp., Inc., 847

So. 2d 244, 246 (La. Ct. App. 2003) (“Multiple myeloma is a type of cancer that affects the

bone marrow, the body’s blood-forming system.”).

11

 C. Epidemiological Methodology

One of Petitioner’s experts, Dr. Infante, is an epidemiologist. Epidemiology

“refers to the science that studies the distribution of diseases within populations[.]” Chesson

v. Montgomery Mut. Ins. Co., No. 97, Sept Term, 2012, 2013 WL 5311126, at *17 (Md. Sept.

24, 2013) (internal quotations and citation omitted). Moreover,

[e]pidemiology is a methodology. The practice of
epidemiology involves sampling and matching so as to minimize
systematic bias and statistical analysis designed to estimate the
effect of random errors on results. Epidemiology is not a theory
of how a substance causes cancer, or birth defects, or
autoimmune disease. These theories come from other
disciplines.

4 David L. Faigman et al., Modern Scientific Evidence: The Law and Science of Expert

Testimony § 35-1.1, at 132 n.18 (2002). “[E]pidemiological studies examine existing

populations to attempt to determine if there is an association between a disease or condition

and a factor suspected of causing that disease or condition.” Merrell Dow Pharms. v.

Havner, 953 S.W.2d 706, 715 (Tex. 1997). The issue of an epidemiological “association”

has been more fully described as follows:

[T]he field of epidemiology is not intended to utilize the results
of a group study to demonstrate causation for any individual
plaintiff. Instead, the studies are performed or undertaken to
first determine if a statistically significant association exists
between an exposure and an outcome. If such an association is
revealed and the studies are determined to be free of
confounding, bias, or other error, then an association can be
established. At this point, epidemiologists and others
interpreting the epidemiologic data can make an inference

12

 vis-à-vis the existence of a causal relationship or the lack
thereof.

David C. Woodside, III and Allison G. Davis, The Bradford Hill Criteria: The Forgotten

Predicate, 35 T. Jefferson L. Rev. 103, 108 (2013).

It should be clearly understood that the term “association” is a term of art in

epidemiology. It has been defined as “[t]he degree of statistical dependence between two or

more events or variables.” In re TMI Litig., 193 F.3d 613, 710 n.159 (3d Cir. 1999) (internal

quotations and citation omitted). Moreover, an association is not the same as causation. An

epidemiological association identified in a study may or may not be causal. “Although

epidemiological studies cannot prove causation, they do provide a basis for an epidemiologist

to infer that a chemical agent can cause a disease.” Syl. pt. 7, King v. Burlington Northern

Santa Fe Ry. Co., 762 N.W.2d 24, 28 (Neb. 2009). “Assessing whether an association is

causal requires an understanding of the strengths and weaknesses of the study’s design and

implementation, as well as a judgment about how the study findings fit with other scientific

knowledge.” Michael D. Green et al., Reference Guide on Epidemiology, in Reference

Manual on Scientific Evidence 549, 553 (3d ed. 2011). Moreover, the methodological

soundness of an epidemiological study and its use in resolving causation require answering

three questions. First, does the study reveal an association between a chemical agent and

disease? Second, did any errors in the study cause an inaccurate result? Third, is the

relationship between the chemical agent and the disease causal? See id. at 554.

13

 In determining whether an association exists between a suspected chemical

agent and a disease, epidemiologist primarily rely upon three types of studies: (1)

experimental studies, (2) cohort studies, and (3) case-control studies.8 See King, 762 N.W.2d

at 35. Finally, the strength of an association between exposure to a chemical agent and

disease can be stated as a relative risk, an odds ratio, or an attributable risk. “Each of these

measurements of association examines the degree to which the risk of disease increases when

individuals are exposed to an agent.” Green et al., supra, at 566. To better understand this

epidemiological association, we will review these three main types of studies – experimental

studies, cohort studies, and case control studies as well as studies that examine the

association of relative risk, odds ratio, and attributable risk.

1. Experimental studies. An experimental study has been defined as “a study

in which a population is selected for a planned trial of a regimen whose effects are measured

by comparing the outcome of the regime in the experimental group with the outcome of

another regimen in a control group.” 4 Faigman et al., supra, at 184. This type of study goes

by several names including, randomized trial, clinical trial, and true experiment. Green et al.

supra, at 555.

8
There are also additional types of specialized studies.

14

 In order to answer the question of whether a chemical agent is related to a

certain disease, an epidemiologist may conduct an experimental study in which selected

participants are randomly assigned to one, of two groups: a group exposed to the chemical

agent and a group that was not exposed. After a predetermined observation period, the

participants in both groups are evaluated for the development of the disease. An

experimental study is often used to evaluate new drugs or medical treatments. Green et al.,

supra, at 555. See also In re Bextra & Celebrex Mktg. Sales Practices & Prod. Liab. Litig.,

524 F. Supp. 2d 1166 (N.D. Cal. 2007) (wherein a clinical study that revealed Celebrex

increased cardiovascular risk was relied upon by the court to conclude that the plaintiff’s

experts’ testimony on causation was admissible); McDarby v. Merck & Co., 949 A.2d 223

(N.J. Super. Ct. App. Div. 2008) (explaining how clinical trials of Vioxx revealed an

association with heart disease).

Of course, if a chemical agent’s effects are harmful, a researcher cannot

knowingly expose participants to the chemical. In situations where the chemical agent is

harmful, a researcher will typically “observe” selected participants who have already been

exposed to the chemical, e.g., comparing those already exposed to an industrial chemical

agent with another group of participants who have not been exposed. In this situation, the

researcher compares the rate of disease or death of the exposed group with that of an

unexposed group. Green et al., supra, at 555-56.

15

 2. Cohort studies. A cohort study has been defined as an “analytical method

of epidemiologic study in which subsets of a defined population can be identified who . . .

have been . . . exposed . . . to a factor . . . hypothesized to influence the probability of

occurrence of a given disease[.]” Faigman et al., supra, at 183. A cohort study is also called

a prospective study and followup study. Green et al., supra, at 557.

A cohort study involves the use of a study population without regard to the

disease status of the participants. A researcher may define a study population in the present

and follow it into the future, or design a study population retrospectively at a point in the past

and follow it over historical time toward the present. In either situation, the researcher will

classify the study population into groups based on whether the group members were exposed

to the chemical agent of interest. The task of a researcher in a retrospective population study

is to determine the number of people in the exposed group who developed the disease of

interest, from all available reliable sources, and compare that number of people with the

number of people of the group who were not exposed. With respect to a prospective study,

the exposed and unexposed populations are followed for a predetermined length of time, and

the number of persons in each group who develop the disease of interest are compared.

Green et al., supra, at 557. See also Faigman et al., supra, at 162-65.

16

 A cohort study has the advantage of allowing the temporal relationship between

exposure and disease to be established more quickly than in other study design. As a result

of following a study population that is not initially affected by the disease, the researcher is

able to determine the exact onset time of the disease and its relation to exposure to the

chemical. For a researcher, “[t]his temporal relationship is critical to the question of

causation, because exposure must precede disease onset if exposure caused the disease.”

Green et al, supra, at 558.

3. Case control studies. A case control study involves selecting a group of

individuals who have a disease of interest (cases), and choosing a similar group of persons

who do not have the disease of interest (controls). When the groups are selected, the

researcher will then compare them in terms of past exposures. In doing so, the researcher is

seeking to determine whether a certain exposure that is associated with the disease resulted

in a higher proportion of past exposure among the “cases” than among the “controls”.

“[C]ase-control studies are . . . particularly useful in the study of rare diseases, because if a

cohort study were conducted, an extremely large group would have to be studied in order to

observe the development of a sufficient number of cases for analysis.” Green et al., supra,

at 559. See also 4 Faigman et al., supra, at 166-69.

17

 4. Relative risk. The strength of an association between exposure to a

chemical agent and disease can be stated as a relative risk. This concept of “relative risk”

is defined as the ratio of the incidence rate of a targeted disease in an exposed population to

the incidence rate in an unexposed population. Additionally, the “incidence rate of a targeted

disease” is defined as the total number of cases of the disease that manifests itself during a

predetermined time period divided by the number of individuals in the population being

studied. In sum, the incidence rate illustrates the risk that an individual in a population group

will develop the targeted disease within a predetermined time period. Green et al., supra, at

566-67.

For example, assume that a group composed of 100 individuals is exposed to

a chemical agent, and a group composed of 200 individuals is not exposed to the chemical.

After a researcher studies both groups for one year, it is learned that 40 of the individuals

exposed to the chemical have the targeted disease, and 20 of the individuals who were not

exposed to the chemical are also found to have the disease. The relative risk of contracting

the disease would be determined as follows:

[1] The incidence rate of disease in the exposed individuals is 40
cases per year per 100 persons (40/100), or 0.4.

[2] The incidence rate of disease in the unexposed individuals
is 20 cases per year per 200 persons (20/200), or 0.1.

18

 [3] The relative risk is calculated as the incidence rate in the
exposed group (0.4) divided by the incidence rate in the
unexposed group (0.1), or 4.0.

Green et al., supra, at 567. As a general matter, the relative risk is interpreted as follows:

[1] If the relative risk equals 1.0, the risk in exposed individuals
is the same as the risk in unexposed individuals. There is no
association between exposure to the agent and disease.

[2] If the relative risk is greater than 1.0, the risk in exposed
individuals is greater than the risk in unexposed individuals.
There is a positive association between exposure to the agent
and the disease, which could be causal.

[3] If the relative risk is less than 1.0, the risk in exposed
individuals is less than the risk in unexposed individuals. There
is a negative association, which could reflect a protective or
curative effect of the agent on risk of disease. . . .

Green et al., supra, at 566-67. See also Daniel J. Brown, Clear as Mud – The Role of

Epidemiological Data in Assessing Admissibility under Delaware Rule of Evidence 702, 13

Del. L. Rev. 71, 79 (2012) (“The size of the relative risk indicates the strength of that

association. For example, a relative risk of 3.5 means the risk of disease in those exposed

to the substance is three and half times higher than the risk of disease in those who were not

exposed.”).

5. Odds ratio. The odds ratio, like the relative risk, is used to illustrate in

quantitative terms the association between exposure to a chemical agent and a disease. This

tool is considered an easy way to estimate the risk in a case-control study when a rare disease

19

is under investigation.9 The odds ratio permits an approximation of the risk when a rare

disease is the focus of the study. The odds ratio, in a case-control study, is the ratio of the

odds that a case group (one with the disease) was exposed to a chemical agent to the odds

that a control group (one without the disease) was exposed to the same chemical. However,

in a cohort study, the odds ratio is expressed as the ratio of the odds of developing a disease

when exposed to a chemical to the odds of developing the disease when not exposed to the

chemical. Green et al., supra, at 568.

For example, a researcher conducts a case-control study that has 100

individuals with a disease who act as the “case” group, and 100 individuals who do not have

the disease act who were the “control” group. It is found that 40 of the 100 case group

individuals were exposed to a chemical agent, and 60 were not. In the control group, 20

9
It has been noted that

[a] relative risk cannot be calculated for a case-control
study, because a case-control study begins by examining a group
of persons who already have the disease. That aspect of the
study design prevents a researcher from determining the rate at
which individuals develop the disease. Without a rate or
incidence of disease, a researcher cannot calculate a relative
risk.

Green et al., Reference Guide on Epidemiology, in Reference Manual on Scientific Evidence
549, 568 n.58 (3d ed. 2011).

20

individuals were exposed to the chemical, and 80 were not. The calculation of the odds ratio

would be as follows:

(40/60)

OR = ——— = 2.67

(20/80)

Green et al., supra, at 569.

[B]ecause an odds ratio approximates the relative risk, the same
general rules of interpretation apply, i.e., an odds ratio of 1.0
indicates that there is no association between exposure and
disease, whereas an odds ratio above 1.0 indicates a positive
association and an odds ratio below 1.0 indicates a negative
association.

Brown, supra, 13 Del. L. Rev. at 79.

6. Attributable risk. Another epidemiological measurement of risk is called

attributable risk. This measurement tool represents the amount of disease that individuals are

exposed to that may be attributed to such exposure. Attributable risk also can be formulated

as the proportion of the disease among exposed individuals that is linked to the exposure.

“[T]he attributable risk reflects the maximum proportion of the disease that can be attributed

to exposure to an agent and consequently the maximum proportion of disease that could be

potentially prevented by blocking the effect of the exposure or by eliminating the exposure.”

Green et al., supra, at 570. Stated differently, if the epidemiological association of the

disease and chemical agent is causal, “the attributable risk is the proportion of disease in an

21

exposed population that might be caused by the agent and that might be prevented by

eliminating exposure to that agent.” Id.

The following example has been given to illustrate the determination of

attributable risk:

For example, if the incidence rate in the unexposed group
is ten and the incidence rate in the exposed is fifty then the
attributable risk is 80 percent (i.e., 50-10 = 40; 40/50 = 80%).
This would mean that 80 percent of the disease in the exposed
group is attributable to the exposure to the suspect substance.
This, however, is not the same as stating that 80 percent of the
disease is caused by the exposure.

Brown, supra, 13 Del. L. Rev. at 80.

D. Toxicological Methodology

Another of the Petitioner’s experts, Dr. Goldstein, is a toxicologist. The record

also shows that one of the experts called by CSX, Dr. Green, is likewise a toxicologist.

“[T]he science of toxicology can help understand whether the dose of a substance achieved

following a particular exposure has any relationship to toxicity or disease.” David L. Eaton,

Scientific Judgment and Toxic Torts–Primer in Toxicology for Judges and Lawyers, 12 J.L.

& Pol’y 5, 12 (2003). Toxicology is a science that focuses on understanding and identifying

22

the harmful effects of chemical agents.10 Toxicological studies alone do not purport to

provide direct evidence a disease was caused by a chemical exposure. This discipline can,

however, be instrumental in offering scientific data regarding the increased risk of

contracting a disease based upon dosage. Bernard D. Goldstein and Mary Sue Henifin,

Reference Guide on Toxicology, in Reference Manual on Scientific Evidence 633, 635-37

(3d ed. 2011). Courts have held that toxicologists can provide expert testimony on whether

a chemical agent caused a disease. See Bonner v. ISP Techs., Inc., 259 F.3d 924, 928-31 (8th

Cir. 2001); Loudermill v. Dow Chem. Co., 863 F.2d 566, 569–70 (8th Cir. 1988).11

10
“The discipline of toxicology is based primarily upon the sciences of
chemistry and biology.” 4 Faigman et al., Modern Scientific Evidence: The Law and Science
of Expert Testimony § 35-1-1, at 104 (2002).
11
One commentator summarized the science of toxicology as follows:

There are three basic tenets of toxicology: (1) all
chemicals have the potential to be harmful given the right
dosage; (2) many chemical agents have a signature pattern of
toxic effects that are used to establish causation; and (3)
responses in laboratory animals are useful in determining the
potential effects on humans. Toxicology generally seeks to
identify chemicals that pose a threat to human populations and
the risks associated with a chemical exposure at a given dose.
Unlike epidemiology, which seeks primarily to establish
causation, toxicology seeks primarily to estimate the given risks
associated with potential exposure.

Carl H. Johnson, When Science Is Too Daunting: Multiple Chemical Sensitivity, Federal
Courts, and the Struggling Spirit of Daubert, 1 Vill. Envtl. L.J. 273, 291-92 (2000). See also
4 Faigman et al., supra note 10, at 107.

23

 “[D]ata from properly designed and evaluated studies in experimental animals

have been and continue to be reliable sources of information for the identification of

potential human health hazards and the estimation of risks in exposed populations.” Ronald

L. Melnick and John R. Bucher, Determining Disease Causality From Experimental

Toxicology Studies, 15 J.L. & Pol’y 113, 133 (2007). See also 4 Faigman et al., supra, at 109

(“There is an overwhelming biological similarity between humans and other animals,

particularly mammals.”). The general testing procedure used by toxicologists involves

exposing laboratory animals12 or cells/tissues13 to a chemical agent, monitoring changes, and

comparing those changes with those for an unexposed control group. Of course, there is an

ongoing debate as to the extent to which animal testing will validly reflect human responses

to a chemical agent. This debate, however, is circular because it is unethical and potentially

criminal to experiment on humans by exposing them to hazardous doses of a chemical agent.

Thus, animal toxicological studies provide the best readily accessible scientific data

concerning the risk of disease from a chemical exposure. Goldstein and Henifin, supra, at

639.14

12
This is called in vivo research.
13
This is called in vitro research.
14
The justification and reliability of animal studies for the potential effects of
chemicals on humans has been stated as follows:

Why are animal models used to evaluate human risk?
The most obvious explanation is that it is unethical to test for
(continued...)

24

 A central component of a toxicological study will involve dose-response

relationships. 4 Faigman, supra, at 107-08. That is, experiments with animals are conducted

to determine the dose-response relationship of a chemical agent by measuring how the

response varies with different doses. Information obtained from this technique “is useful in

understanding the mechanisms of toxicity and extrapolating data from animals to humans.”

Goldstein and Henifin, supra, at 641. In making a causation opinion about a chemical and

a disease, a toxicologist will consider the extent of a person’s dose exposure. Goldstein and

Henifin, supra, at 638.15

14
(...continued)
adverse health effects, such as cancer, in humans through
intentional exposures. Just as animal models are used in
preclinical trials of new pharmaceutical agents before testing in
humans, experimental studies performed on animals have been
used to assess potential health risks of toxic and carcinogenic
agents in our workplace and general environment. The
predictive value of animal studies is based on species
similarities in the biological processes of disease induction.
Another major advantage of animal studies is the elimination of
the need to wait for a high incidence of human cancers, which
may take as much as 30 years from time of first exposure to
clinical manifestation of disease, before implementing public
health protective strategies.

Melnick and Bucher, Determining Disease Causality From Experimental Toxicology Studies,
15 J.L. & Pol’y 113, at 115-16 (2007).
15
The following is an explanation and illustration of dose:

Dose is a function of both concentration and duration.
Haber’s rule is a century-old simplified expression of dose
effects in which the effect of a concentration and duration of
(continued...)

25

 The approach taken by toxicologists for assessing exposure to a harmful

chemical agent has been summarized as follows:

Exposure assessment methodologies include mathematical
models predicting exposure resulting from an emission source,
which might be a long distance upwind; chemical or physical
measurements of media such as air, food, and water; and
biological monitoring within humans, including measurements
of blood and urine specimens. An exposure assessment should
also look for competing exposures. In this continuum of
exposure metrics, the closer to the human body, the greater the
overlap with toxicology.

Goldstein and Henifin, supra, at 657.

15
(...continued)
exposure is a constant (e.g., exposure to an agent at 10 parts per
million for 1 hour has the same impact as exposure to 1 part per
million for 10 hours). Exposure levels, which are concentrations,
are often confused with dose. This can be particularly
problematic when attempting to understand the implications of
exposure to a level that exceeds a regulatory standard that is set
for a different time frame. For example, assume a drinking water
contaminant is a known cause of cancer. To avoid a 1 in
100,000 lifetime risk caused by this contaminant in drinking
water, and assuming that the average person will drink
approximately 2000 mL of water daily for a lifetime, the
regulatory authority sets the allowable contaminant standard in
drinking water at 10 µg/L. Drinking one glass of water
containing 20 µg/L of this contaminant, although exceeding the
standard, does not come close to achieving a “reasonably
medically probable” cause of an individual case of cancer.

Goldstein and Henifin, Reference Guide on Toxicology, in Reference Manual on Scientific
Evidence 633, 638 n.12 (3d ed. 2011).

26

 A toxicologist’s opinion on causation should be based upon three preliminary

assessments:

First, the expert should analyze whether the disease can
be related to chemical exposure by a biologically plausible
theory. Second, the expert should examine whether the plaintiff
was exposed to the chemical in a manner that can lead to
absorption into the body. Third, the expert should offer an
opinion about whether the dose to which the plaintiff was
exposed is sufficient to cause the disease.

Goldstein and Henifin, supra, at 661. See also Eaton, supra, 12 J.L. & Pol’y at 38-40;

Robert C. James, Role of Toxicology in Toxic Tort Litigation: Establishing Causation, 61

Def. Couns. J. 28, 29 (1994). Courts also have recognized a “three-step methodology for

toxicologists endorsed by the World Health Organization[.]” Young v. Burton, 567

F. Supp. 2d 121, 129 (D.D.C. 2008). The risk assessment methodology has been described

as follows:

First, an evaluation is made of the chemicals to which the
individual might have been exposed, and of the concentrations
of these chemicals in air breathed by the individual. The second
step involves an evaluation, based on the published scientific
literature, of the exposures necessary to produce the adverse
effects associated with the chemicals to which individuals may
be exposed. These two evaluations are then combined in the
final step of the risk assessment to provide an estimate of the
likelihood that any of the harmful properties of any or all of the
chemicals might have been expressed in the exposed individual.

Bombardiere v. Schlumberger Tech. Corp., 934 F. Supp. 2d 843, 848-49 (N.D. W. Va. 2013).

See also Evans v. Toyota Motor Corp., No. V-03-09, 2005 WL 3454456, at*4 (S.D. Tex.

Aug. 9, 2005); Roche v. Lincoln Prop. Co., 278 F. Supp. 2d 744, 754 (E.D. Va. 2003);

27

Mancuso v. Consolidated Edison Co. of New York, Inc., 967 F. Supp. 1437, 1445 (S.D.N.Y.

1997); Cavallo v. Star Enter., 892 F. Supp. 756, 764 (E.D. Va. 1995), aff’d, in part, and

rev’d, in part, 100 F.3d 1150 (4th Cir. 1996); Craig T. Smith, Peering into the Microscope:

The Rise of Judicial Gatekeeping after Daubert and its Effect on Federal Toxic Tort

Litigation, 13 B.U. J. Sci. & Tech. L. 218, 227 (2007); Neal C. Stout and Peter A. Valberg,

Bayes’ Law, Sequential Uncertainties, and Evidence of Causation in Toxic Tort Cases, 38

U. Mich. J.L. Reform 781, 900 (2005).

E. Weight of the Evidence Methodology

One of the Petitioner’s experts, toxicologist Dr. Goldstein, indicated during his

testimony that he relied upon the weight of the evidence methodology in rendering his

opinion.16 “[T]he term ‘weight of evidence’ is used to characterize a process or method in

which all scientific evidence that is relevant to the status of a causal hypothesis is taken into

account.” Sheldon Krimsky, The Weight of Scientific Evidence in Policy and Law, 95 Am.

J. Pub. Health S129 (2005). Under this approach, an “expert considers all available studies

and determines the weight to be afforded to each on the basis of the strengths and weaknesses

of the individual studies.” Thomas O. McGarity and Sidney A. Shapiro, Regulatory Science

16
It was previously indicated that CSX’s expert, Dr. Green, is a toxicologist.
However, her testimony was far too acrimonious and rambling to clearly understand what
precise methodology she used.

28

in Rulemaking and Tort: Unifying the Weight of the Evidence Approach, 3 Wake Forest J.L.

& Pol’y 65, 78 (2013).

The phrase “weight of the evidence” is often accorded different meanings by

scientists. As explained by one court:

The weight of evidence method [WOE] is used in
medical literature either in a rigorous scientific or metaphorical
sense. It is used as methodology where WOE points to
established interpretative methodologies (e.g., systematic
narrative review, meta-analysis, causal criteria, and/or quality
criteria for toxicological studies). . . . The metaphorical use of
the term is, if nothing else, a colorful way to say the body of
evidence we have examined and judged using a method we have
not described but could be more or less inferred from a careful
between-the-lines reading of our paper.

Reeps ex rel. Reeps v. BMW of N. Am., LLC, No. 100725/08, 2013 WL 2362566, at *3

(N.Y. Sup. Ct., May 10, 2013) (internal quotations and citations omitted)).17 The weight of

17
The different ways in which weight of the evidence may be used by scientists
have been summarized as follows:

WOE has several distinct uses in contemporary scientific
practice. First, it most often appears in a metaphorical sense,
pointing to a body of scientific evidence without reference to
any specific methodology. . . . Second, in some situations, a
WOE approach specifically refers to a technique in which “all
available evidence” should be examined and interpreted. . . .
Third, often a WOE method refers directly to some other
synthetic method, such as the systematic narrative review,
meta-analysis, or the so-called “causal criteria” associated most
often with the public health discipline of epidemiology. Fourth,
(continued...)

29

the evidence methodology is used by regulatory agencies such as the Environmental

Protection Agency18 and the Occupational Safety and Health Administration. “Regulatory

agencies or risk analysis panels use [the weight of evidence method] to assess the total value

of the scientific evidence that a substance may be dangerous to human health.” Krimsky,

17
(...continued)
a WOE method may point to an institutional approach to
synthesis. . . . Finally, in relatively rare instances of health-risk
assessment, a WOE approach involves a method that assigns
numerical weights to individual scientific studies and creates
summary numeric assessments using mathematical algorithms.

Douglas L. Weed, Evidence Synthesis and General Causation: Key Methods and an
Assessment of Reliability, 54 Drake L. Rev. 639, 639 (2006).
18
In the EPA’s 2005 “Guidelines for Carcinogen Risk Assessment” it described
the type of data that would be considered in its weight of the evidence methodology:

1.3.3. Weight of Evidence Narrative

The cancer guidelines emphasize the importance of
weighing all of the evidence in reaching conclusions about the
human carcinogenic potential of agents. This is accomplished in
a single integrative step after assessing all of the individual lines
of evidence. . . . Evidence considered includes tumor findings,
or lack thereof, in humans and laboratory animals; an agent’s
chemical and physical properties; its structure-activity
relationships (SARs) as compared with other carcinogenic
agents; and studies addressing potential carcinogenic processes
and mode(s) of action, either in vivo or in vitro. Data from
epidemiologic studies are generally preferred for characterizing
human cancer hazard and risk.

U.S. Environmental Protection Agency, Guidelines for Carcinogen Risk Assessment 1-11
(2005), http://www.epa.gov/ttn/atw/cancer_guidelines_final_3-25-05.pdf (last visited on
Nov. 8, 2013).

30

supra, at S139. See also King, 762 N.W.2d at 39-40 (“[G]overnment agencies and some

experts use a weight-of-the-evidence methodology. That methodology comprehensively

analyzes the data from different scientific fields, primarily animal tests and epidemiological

studies, to assess carcinogenic risks.”). In commenting upon the weight of the evidence

methodology, Justice Stevens noted the following:

[T]he Court of Appeals expressly decided that a “weight of the
evidence” methodology was scientifically acceptable. To this
extent, the Court of Appeals’ opinion is persuasive. It is not
intrinsically “unscientific” for experienced professionals to
arrive at a conclusion by weighing all available scientific
evidence—this is not the sort of “junk science” with which
Daubert was concerned.

General Elec. Co. v. Joiner, 522 U.S. 136, 153, 118 S. Ct. 512, 522-23, 139 L. Ed. 2d 508

(1997) (Stevens, J., concurring, in part, and dissenting, in part).

The court in Milward v. Acuity Specialty Products Group, Inc., 639 F.3d 11

(1st Cir. 2011), explained the weight of the evidence methodology as follows:

This “weight of the evidence” approach to making causal
determinations involves a mode of logical reasoning often
described as “inference to the best explanation,” in which the
conclusion is not guaranteed by the premises. . . . [I]nference to
the best explanation can be thought of as involving six general
steps, some of which may be implicit. The scientist must (1)
identify an association between an exposure and a disease, (2)
consider a range of plausible explanations for the association,
(3) rank the rival explanations according to their plausibility, (4)
seek additional evidence to separate the more plausible from the
less plausible explanations, (5) consider all of the relevant
available evidence, and (6) integrate the evidence using

31

 professional judgment to come to a conclusion about the best
explanation.

....

The fact that the role of judgment in the weight of the
evidence approach is more readily apparent than it is in other
methodologies does not mean that the approach is any less
scientific. No matter what methodology is used, an evaluation
of data and scientific evidence to determine whether an
inference of causation is appropriate requires judgment and
interpretation. The use of judgment in the weight of the
evidence methodology is similar to that in differential diagnosis,
which we have repeatedly found to be a reliable method of
medical diagnosis.

Milward, 639 F.3d at 17-18 (internal quotations and citations omitted). See also Thomas O.

McGarity and Sidney A. Shapiro, Regulatory Science in Rulemaking and Tort: Unifying the

Weight of the Evidence Approach, 3 Wake Forest J.L. & Pol’y 65, 97 (2013) (“Both common

law courts and regulatory agencies should consider expert opinion based on weight of the

evidence evaluations of the available scientific information in accordance with valid

scientific criteria, such as the Bradford Hill criteria, for evaluating evidence.”); Kimberly

Gordy, The 9/11 Cancer Conundrum: The Law, Policy, & Politics of the Zadroga Act, 37

Seton Hall Legis. J. 33, 83 (2012) (“The Milward court . . . provides useful guidance for

weighing evidence. . . . It endorsed the ‘weight of the evidence’ approach, which

encompasses the Bradford Hill methodology.”).

F. Bradford Hill Methodology

32

 Petitioner’s experts, Dr. Durie and Dr. Infante, relied upon the Bradford Hill

methodology in rendering their opinions. The record also showed that the expert for CSX,

Dr. Shield, relied upon the Bradford Hill Methodology. This methodology involves the use

of criteria set out by epidemiologist Sir Austin Bradford Hill in an article he published in

1965. See Sir Austin Bradford Hill, The Environment and Disease: Association or

Causation?, 58 Proc. Royal Soc’y Med. 295 (1965). The Bradford Hill criteria, as they are

called,19 are “considered relevant for determining whether an epidemiologically-observed

correlation between a potential causal agent and a disease can or cannot legitimately be

treated as a cause rather than as merely an association.” Jennifer L. Mnookin, Atomism,

Holism, and the Judicial Assessment of Evidence, 60 UCLA L. Rev. 1524, 1524 (2013).

Stated differently, the Bradford Hill criteria are factors that are considered when a researcher

seeks to determine whether an observed epidemiological association between a disease and

a chemical agent is causal. Nonnon v. City of New York, 932 N.Y.S.2d 428, 433 (2011). See

also Gannon v. United States, 571 F. Supp. 2d 615, 624 (E.D. Pa. 2007) (“Other preeminent

scientists have relied on and adapted the Bradford Hill criteria to determine whether a virus

can be deemed to cause human cancer.”). “[C]ourts that have considered the question have

held that it is not proper methodology for an epidemiologist to apply the Bradford Hill factors

19
They are also known as the Bradford Hill viewpoints. See Magistrini v. One
Hour Martinizing Dry Cleaning, 180 F. Supp. 2d 584, 592 n.9 (D.N.J. 2002) (“These factors,
first set forth by Sir Austin Bradford Hill, also have been referred to as ‘viewpoints’[.]”).

33

without data from controlled studies showing an association.” In re Fosamax Prods. Liab.

Litig., 645 F. Supp. 2d 164, 188 (S.D.N.Y. 2009).

The Bradford Hill criteria include: (1) strength of the association, (2)

consistency of the association, (3) specificity of the association, (4) temporal relationship of

the association, (5) biological gradient or dose-response curve of the association, (6)

plausibility of the causation, (7) coherence of the explanation, (8) experimental data, and (9)

existence of analogous causal relationships. Hill, supra, 58 Proc. Royal Soc’y Med. at 295­

99. See also Watson v. Dillon Cos., Inc., 797 F. Supp. 2d 1138, 1150 (D. Colo. 2011);

Merrell Dow Pharms., Inc. v. Havner, 953 S.W.2d 706, 718-19 (Tex. 1997).20

The Bradford Hill criteria are “not exhaustive and that no one type of evidence

must be present before causality may be inferred.” Milward, 639 F.3d at 17. See also In re

Asbestos Litig., 900 A.2d 120, 134-35 (Del. Super. Ct. 2006) (“None of these criteria stand

alone; they are all important when considering the issues of association and risk.”). That is,

“one or more of the factors may be absent even where a causal relationship exists[.]”

20
The “weight of the evidence” methodology can be used along with the
Bradford Hill criteria. See Milward, 639 F.3d at 17.

34

Magistrini v. One Hour Martinizing Dry Cleaning, 180 F. Supp. 2d 584, 592 n.9 (D.N.J.

2002).21 Comments on each of the Bradford Hill criteria follow.

1. Strength of association. Showing that a strong association exists between

a chemical agent and a disease is more likely indicative of a causal relationship. That is, the

stronger the relationship between the chemical agent and the disease, the less likely it is that

the relationship is due to chance or an extraneous variable (a confounder). Hill provided the

following example of this criterion:

To take a more modern and more general example upon
which I have now reflected for over fifteen years, prospective
inquiries into smoking have shown that the death rate from
cancer of the lung in cigarette smokers is nine to ten times the
rate in non-smokers and the rate in heavy cigarette smokers is
twenty to thirty times as great. On the other hand the death rate
from coronary thrombosis in smokers is no more than twice,
possibly less, the death rate in nonsmokers. Though there is
good evidence to support causation it is surely much easier in

21
This point also was emphasized by Hill, who cautioned in his article:

None of my nine viewpoints can bring indisputable
evidence for or against the cause and effect hypothesis and none
can be required as a sine qua non. What they can do, with
greater or less strength, is to help us to make up our minds on
the fundamental question-is there any other way of explaining
the set of facts before us, is there any other answer equally, or
more, likely than cause and effect?

Sir Austin Bradford Hill, The Environment and Disease: Association or Causation? , 58
Proc. Royal Soc’y Med. 295, 299 (1965).

35

 this case to think of some features of life that may go
hand-in-hand with smoking – features that might conceivably be
the real underlying cause or, at the least, an important
contributor, whether it be lack of exercise, nature of diet or other
factors. But to explain the pronounced excess in cancer of the
lung in any other environmental terms requires some feature of
life so intimately linked with cigarette smoking and with the
amount of smoking that such a feature should be easily
detectable.

Hill, supra, 58 Proc. Royal Soc’y Med. at 295-96. See also King, 762 N.W.2d at 40

(“[R]egarding an association’s strength, the higher the relative risk, the greater the likelihood

that a relationship is causal. Yet lower relative risks can reflect causality.”).

2. Consistency of the association. The consistency of association criterion

seeks to determine whether a similar association may be found in a variety of different

situations. Showing numerous observations of an association, with different people in

diverse situations with different measurement tools, will increase the credibility of an

association finding. Hill provided the following commentary on this factor:

This requirement may be of special importance for those
rare hazards singled out in the Section’s terms of reference.
With many alert minds at work in industry today many an
environmental association may be thrown up. Some of them on
the customary tests of statistical significance will appear to be
unlikely to be due to chance. Nevertheless whether chance is
the explanation or whether a true hazard has been revealed may
sometimes be answered only by a repetition of the circumstances
and the observations.

Returning to my more general example, the Advisory
Committee to the Surgeon-General of the United States Public

36

 Health Service found the association of smoking with cancer of
the lung in 29 retrospective and 7 prospective inquiries. The
lesson here is that broadly the same answer has been reached in
quite a wide variety of situations and techniques. In other words
we can justifiably infer that the association is not due to some
constant error or fallacy that permeates every inquiry. And we
have indeed to be on our guard against that.

Hill, supra, 58 Proc. Royal Soc’y Med. at 296. See also Frank C. Woodside, III and Allison

G. Davis, The Bradford Hill Criteria: The Forgotten Predicate, 35 T. Jefferson L. Rev. 103,

116 (2013) (“Reduced to an elementary level, consistency demonstrates that the results of a

particular study are not an outlier result. Consistency indicates that the results are generally

concurrent with the results of other studies–not that they are generally accepted.”).

3. Specificity of the association. The specificity factor seeks to show that an

effect, e.g., lung cancer, has only one cause, smoking. Hill discussed this factor as follows:

If, as here, the association is limited to specific workers
and to particular sites and types of disease and there is no
association between the work and other modes of dying, then
clearly that is a strong argument in favour of causation.

....

Coming to modern times the prospective investigations
of smoking and cancer of the lung have been criticized for not
showing specificity - in other words the death rate of smokers is
higher than the death rate of non-smokers from many causes of
death. But here surely one must return to my first characteristic,
the strength of the association. If other causes of death are raised
10, 20 or even 50% in smokers whereas cancer of the lung is
raised 900-1,000% we have specificity–a specificity in the
magnitude of the association.

37

 We must also keep in mind that diseases may have more
than one cause. It has always been possible to acquire a cancer
of the scrotum without sweeping chimneys or taking to
mulespinning in Lancashire. One-to-one relationships are not
frequent. Indeed I believe that multicausation is generally more
likely than single causation though possibly if we knew all the
answers we might get back to a single factor.
In short, if specificity exists we may be able to draw
conclusions without hesitation; if it is not apparent, we are not
thereby necessarily left sitting irresolutely on the fence.

Hill, supra, 58 Proc. Royal Soc’y Med. at 297. See also Woodside and Davis, supra, 35 T.

Jefferson L. Rev. at 116 (“The crux of the specificity consideration is that causation is likely

if a very specific population at a specific site develops a disease with no other likely

explanation. More specifically, well performed studies demonstrating an association

between a specific exposure and a clearly defined disease or condition–otherwise known as

the case definition–are of more value in inferring the existence of a causal relationship than

studies with poorly defined exposures and/or loosely defined diseases or conditions.”).

4. Temporal relationship of the association. This factor seeks to assure that

the exposure to a chemical agent preceded the disease by a reasonable amount of time, i.e.,

a cause must precede an effect in time. Hill commented briefly on this factor as follows:

My fourth characteristic is the temporal relationship of
the association–which is the cart and which the horse? This is a
question which might be particularly relevant with diseases of
slow development. Does a particular diet lead to disease or do
the early stages of the disease lead to those peculiar dietetic
habits? Does a particular occupation or occupational
environment promote infection by the tubercle bacillus or are

38

 the men and women who select that kind of work more liable to
contract tuberculosis whatever the environment–or, indeed, have
they already contracted it? This temporal problem may not arise
often but it certainly needs to be remembered, particularly with
selective factors at work in industry.

Hill, supra, 58 Proc. Royal Soc’y Med. at 298. See also Woodside and Davis, supra, 35 T.

Jefferson L. Rev. at 119 (“Not only must the exposure precede the development of the

alleged symptoms, but the period of time between the alleged exposure and the onset of

symptoms for which compensation is sought must be consistent with the known latency

period for the exposure in question. The latency period is the period of time between

exposure to an agent and manifestation of disease symptoms.”).

5. Biological gradient or dose-response curve of the association. The

biological gradient factor seeks to show or determine whether increased exposure to a

chemical agent increases the incidence of the disease. Hill addressed this factor as follows:

[I]f the association is one which can reveal a biological
gradient, or dose-response curve, then we should look most
carefully for such evidence. For instance, the fact that the death
rate from cancer of the lung rises linearly with the number of
cigarettes smoked daily, adds a very great deal to the simpler
evidence that cigarette smokers have a higher death rate than
non-smokers. That comparison would be weakened, though not
necessarily destroyed, if it depended upon, say, a heavier death
rate in light smokers and a lower rate in heavier smokers. We
should then need to envisage some much more complex
relationship to satisfy the cause-and-effect hypothesis. The clear
dose-response curve admits of a simple explanation and
obviously puts the case in a clearer light.

39

 The same would clearly be true of an alleged dust hazard
in industry. The dustier the environment the greater the
incidence of disease we would expect to see. Often the
difficulty is to secure some satisfactory quantitative measure of
the environment which will permit us to explore this
dose-response. But we should invariably seek it.

Hill, supra, 58 Proc. Royal Soc’y Med. at 298. See also King, 762 N.W.2d at 40 (“A

dose-response relationship is primarily a hallmark of toxicology. If higher exposures to the

agent increase the incidence of disease, the evidence strongly suggests a causal

relationship.”).

6. Plausibility of the causation. Showing that an association is causal is

easier when biological or other facts support such a conclusion. However, such evidence is

not essential. Hill tersely commented on this factor as follows:

It will be helpful if the causation we suspect is
biologically plausible. But this is a feature I am convinced we
cannot demand. What is biologically plausible depends upon
the biological knowledge of the day.

Hill, supra, 58 Proc. Royal Soc’y Med. at 298. See also King, 762 N.W.2d at 41-42 (“When

experts know how a disease develops, an association should show biological consistency

with that knowledge. . . . An expert’s inability to explain a disease’s pathology or

progression goes to the weight of the evidence, not to its admissibility.”).

40

 7. Coherence of the explanation. The viability of an association is enhanced

when it does not conflict with what is known about the study variables, and when competing

plausible theories or hypotheses do not exist. In other words, an association should be

coherent with relevant other knowledge. Hill commented on this factor as follows:

[T]he cause-and effect interpretation of our data should not
seriously conflict with the generally known facts of the natural
history and biology of the disease–in the expression of the
Advisory Committee to the Surgeon-General it should have
coherence.

Thus in the discussion of lung cancer the Committee
finds its association with cigarette smoking coherent with the
temporal rise that has taken place in the two variables over the
last generation and with the sex difference in mortality–features
that might well apply in an occupational problem. The known
urban/rural ratio of lung cancer mortality does not detract from
coherence, nor the restriction of the effect to the lung.

Hill, supra, 58 Proc. Royal Soc’y Med. at 298. See also Woodside and Davis, supra, 35 T.

Jefferson L. Rev. at 123 (“The difference between coherence and plausibility would seem,

in part, to be one of semantics. While plausibility is worded positively (an association should

be in line with substantive knowledge), coherence is presented negatively (an association

should not seriously conflict with substantive knowledge). Consideration of coherence

would reject an observed result as non-causal if it contradicted a predominant theory; while

plausibility leaves the researcher more room regarding which particular piece of substantive

knowledge to evaluate the results against.”).

41

 8. Experimental data. An association can be enhanced by any related research

that is based on experiments. Hill said the following about this factor:

Occasionally it is possible to appeal to experimental, or
semi-experimental, evidence. For example, because of an
observed association some preventive action is taken. Does it
in fact prevent? The dust in the workshop is reduced,
lubricating oils are changed, persons stop smoking cigarettes.
Is the frequency of the associated events affected? Here the
strongest support for the causation hypothesis may be revealed.

Hill, supra, 58 Proc. Royal Soc’y Med. at 298-99. See also Woodside and Davis, supra, 35

T. Jefferson L. Rev. at 124 (“From a scientific standpoint, it is unfortunate that this type of

evidence is generally not available. When an agent’s effects are suspected to be harmful,

researchers cannot knowingly expose people to the agent. It is difficult to design these types

of studies due to the ethical implications of experimentation on humans.”).

9. Existence of analogous causal relationships. This factor seeks to

determine whether an accepted phenomenon in one area can be applied to another area. Hill

tersely commented on this issue as follows:

In some circumstances it would be fair to judge by
analogy. With the effects of thalidomide and rubella before us
we would surely be ready to accept slighter but similar evidence
with another drug or another viral disease in pregnancy.

Hill, supra, 58 Proc. Royal Soc’y Med. at 299. See also Woodside and Davis, supra, 35 T.

Jefferson L. Rev. at 125 (“Recent case law has cast caution upon the extent to which

42

evidence of analogy may be considered in developing opinions on causation. Courts have

warned that a reliable methodology must still be utilized in drawing analogies.”).

G. Qualification, Methodology and Opinion of the Expert Witnesses

As previously mentioned, the three expert witnesses who testified for the

Petitioner at the evidentiary hearing were Dr. Infante, Dr. Goldstein and Dr. Durie. CSX

called Dr. Shields and Dr. Green as expert witnesses. In this section we will summarize each

expert’s qualifications, methodology and opinion.

1. Dr. Infante’s qualifications, methodology and opinion. Dr. Infante was

called as an expert witness by Petitioner. Dr. Infante received a Ph.D. in public health from

the Department of Epidemiology at the University of Michigan in 1973.22 Dr. Infante has

published approximately 118 peer reviewed articles in scientific journals, the majority of

which involve epidemiology causation. Dr. Infante’s area of expertise is occupational

environmental epidemiology.

22
Dr. Infante also received a D.D.S. degree from the College of Dentistry at the
Ohio State University in 1966.

43

 In 1973, Dr. Infante worked as a research associate at the University of

Michigan and as an epidemiologic consultant for the World Health Organization in

Washington, D.C. Dr. Infante was employed as an epidemiologist for the Ohio Department

of Health from 1974-1975. During the period 1975-1978, Dr. Infante worked as an

epidemiologist for the National Institute for Occupational Safety and Health (“NIOSH”),

Center for Disease Control, in Cincinnati, Ohio. While working for NIOSH, Dr. Infante

performed epidemiological studies of workers who were exposed to chemical substances that

included benezene, pesticides and vinyl chloride. From 1978-2002, Dr. Infante worked for

the Occupational Safety and Health Administration (“OSHA”), United States Department of

Labor, in Washington, D.C. While with OSHA, Dr. Infante was employed as the Director

of the Office of Carcinogen Identification and Classification (“OCIC”) for five years and as

the Director of the Office of Standards Review (“OSR”) for nineteen years. Dr. Infante’s

work at OCIC included identifying workplace substances that had the ability to cause cancer

and classifying them. Dr. Infante’s work at OSR involved evaluating workplace exposure

to harmful substances and developing occupational exposure limits for substances that were

causing cancer in the workplace. This research work involved developing standards for toxic

workplace substances that included asbestos, arsenic, benzene, cadmium, ethylene oxide and

formaldehyde. From 2002-2011, Dr. Infante was an adjunct professor and lecturer at the

School of Public Health and Health Service, George Mason University.

44

 During his career Dr. Infante has been a consultant or advisor for the World

Health Organization, National Institute of Environmental Health Sciences, Department of

Health and Human Services, National Safety Council, National Academy of Sciences,

National Cancer Institute, Federal Asbestos Taskforce, and the American Public Health

Association. Dr. Infante is a Fellow in the American College of Epidemiology.

Dr. Infante was retained in this litigation to render an epidemiological opinion

as to whether there was an association between diesel exhaust and multiple myeloma, and

whether diesel exhaust caused Mr. Harris’ multiple myeloma. Dr. Infante relied upon the

epidemiological methodology in conjunction with the Bradford Hill criteria.

Dr. Infante reviewed epidemiology literature involving railroad worker diesel

exhaust exposure and multiple myeloma; animal cancer studies related to diesel exhaust

exposures; the effects of diesel exhaust on DNA and human lymphocytes; components of

diesel exhaust that demonstrate an elevated risk of multiple myeloma; and data involving

exposure to two components of diesel exhaust: pristane and benzene.

45

 Dr. Infante testified to reviewing a study by Dr. Tomoko Sonoda et al.,

Meta-Analysis of Multiple Myeloma and Benzene Exposure, 11 J. Epidemiol. 249 (2001),23

which demonstrated a significant association between engine exhaust and multiple myeloma.

Dr. Infante testified that the International Agency for Research on Cancer issued Technical

Publication Number 42 in 2009, and that the publication stated that diesel exhaust exposures

have been linked to multiple myeloma and leukemia. Dr. Infante further testified that in the

third edition of a treatise by David Schottenfeld and Joseph F. Fraumeni, Jr., Cancer

Epidemiology and Prevention, it was reported that studies show an association between

diesel exhaust and elevated risk of multiple myeloma.

The report Dr. Infante prepared for the Petitioner summarized the bases for his

opinion as follows:

23
Dr. Infante defined “meta-analysis” as follows;

A [meta] analysis is an analysis where you pull the data
from a number of studies, and you combine the data, and then
you evaluate the studies that you then select to determine
whether or not there’s an elevated risk of – of the associations
that you’re interested in evaluating.

“Meta-analyses do not involve conducting any new experiments, but are nevertheless highly
regarded in the scientific community for their ability to synthesize a large amount of data and
illustrate a general consensus in a particular field.” State v. Lawson, 291 P.3d 673, 700 n.12
(Or. 2012).

46

 Cohort and case-control studies have demonstrated that
workers exposed to diesel exhaust (DE) have a significantly
elevated risk of death from [multiple myeloma] MM.
Epidemiological studies have also demonstrated chromosomal
damage to B-lymphocytes of workers exposed to diesel exhaust.
Another cancer of the B-cell line, chronic lymphatic leukemia,
also demonstrated a significant association with exposure to
diesel exhaust. Furthermore, benzene, a component of DE, also
has been significantly associated with an elevated risk of
developing MM, and pristane, an additional component of DE,
has demonstrated the induction of plasmacytomas in
experimental animals. These latter tumors are similar to human
MM.

The association between diesel exhaust exposure and
MM has been derived in the face of several factors that limit the
ability to detect such an association through epidemiological
study. The difficulties in identifying an association with MM in
epidemiological study are a reflection of several factors. . . . In
spite of the . . . limitations, several cohort studies of workers
exposed to diesel exhaust now demonstrate elevated risks of
death from MM . . . .

Case-control studies which allow for the recruitment of
much larger cases of MM can be identified in cohort studies also
have been conducted. A large number of these studies
demonstrate a significant association between exposure to diesel
exhaust and MM.

Diesel exhaust also has been demonstrated to cause DNA
damage to the lymphocytes of exposed workers. In addition,
experimental studies demonstrate that diesel exhaust and
components of diesel exhaust, e.g., polycyclic aromatic
hydrocarbons, are mutagenic in experimental test systems, and
cause cancer in experimental animals. Diesel exhaust itself as
well as additional components of diesel exhaust are known to
cause cancer in experimental animals, including lymphoma, and
additional components of DE also demonstrate the induction of
cancer in experimental animals, including lymphomas. This
information provides biological plausibility to the

47

 epidemiological observations related to diesel exhaust and risk
of developing MM.

Ultimately, Dr. Infante opined that there is a significant association between

diesel exhaust and the risk of multiple myeloma and, that “Mr. Harris’ occupational exposure

to [diesel exhaust] between 1978 and 2007 were [sic] significant contributing factors and the

most likely cause of his development of [multiple myeloma].”24

2. Dr. Goldstein’s qualifications, methodology and opinion. Dr. Goldstein

was called as an expert witness by Petitioner. Dr. Goldstein received a Ph.D. in biology in

1962 from the State University of New York, at Buffalo. Dr. Goldstein has published

roughly 60 peer reviewed articles in scientific journals. Dr. Goldstein’s area of expertise is

animal toxicology, specifically with respect to polycyclic aromatic hydrocarbons.25

From 1972 to 1989, Dr. Goldstein worked at the University of California, at

San Francisco, in various capacities, including associate professor in the Department of

24
During his testimony, Dr. Infante acknowledged that he reviewed literature
that did not support his opinion.
25
“Polycyclic aromatic hydrocarbons (PAHs) are a group of over 100 different
chemicals that are formed during the incomplete burning of coal, oil and gas, garbage, or
other organic substances like tobacco or charbroiled meat. PAHs are usually found as a
mixture containing two or more of these compounds, such as soot.” Agency for Toxic
Substances and Disease Registry,
http://www.atsdr.cdc.gov/substances/toxsubstance.asp?toxid=25 (last visited Nov. 8, 2013).

48

Radiology Oncology. From 1989 to 2002, Dr. Goldstein was employed as a researcher by

Electric Power Research Institute (“EPRI”), Palo Alto, California. While at EPRI, Dr.

Goldstein conducted and supervised research involving the toxicological hazards caused by

polycyclic aromatic hydrocarbons that are found in coal tars.26 The World Health

Organization employed Dr. Goldstein in 2002 to evaluate and compare radiation hazards

associated with cell phone use with that of carcinogenic hazards associated with coal tars.

In 2004, the federal Environmental Protection Agency hired Dr. Goldstein to be part of a

group that was charged with the responsibility of revising the approach used to evaluate the

polycyclic aromatic hydrocarbon hazard caused by complex mixtures such as coals.

Dr. Goldstein was retained in this litigation to render an opinion as to whether

diesel exhaust caused multiple myeloma. Dr. Goldstein testified that he relied upon the

weight of the evidence methodology to render his opinion.

Dr. Goldstein reviewed literature from governmental and international agencies

that addressed the issue of whether diesel exhaust caused cancer in general. This literature

included publications from the Environmental Protection Agency,27 International Agency

26
Dr. Goldstein testified that polycyclic aromatic hydrocarbons are found in
diesel exhaust as well as coal tar. He also testified that “[c]hemically they are the same, but
their distribution and concentration within the two sources would vary.”
27
The EPA’s published report concluded the following:
(continued...)

49

for Research on Cancer,28 National Institute of Occupational Science and Health, National

27
(...continued)
II.A.1. Weight-of-Evidence Characterization

Using U.S. EPA’s revised draft 1999 Guidelines for Carcinogen
Risk Assessment (U.S. EPA, 1999), diesel exhaust (DE) is likely
to be carcinogenic to humans by inhalation from environmental
exposures. The basis for this conclusion includes the following
lines of evidence:

[1] strong but less than sufficient evidence for a causal
association between DE exposure and increased lung cancer risk
among workers in varied occupations where exposure to DE
occurs;
[2] extensive supporting data including the demonstrated
mutagenic and/or chromosomal effects of DE and its organic
constituents, and knowledge of the known mutagenic and/or
carcinogenic activity of a number of individual organic
compounds that adhere to the particles and are present in the DE
gases;

[3] evidence of carcinogenicity of DPM and the
associated organic compounds in rats and mice by other routes
of exposure (dermal, intratracheal, and subcutaneous and
intraperitoneal injection); and

[4] suggestive evidence for the bioavailability of DE
organic compounds from DE in humans and animals.

Diesel Engine Exhaust (CASRN N.A.) Integrated Risk Info. Syst., U.S. Envtl. Prot. Agency,
http://epa.gov/IRIS/subst/0642.htm (last visited Nov. 8, 2013).
28
Dr. Goldstein reported data from a 1988 study by IARC, which found diesel
exhaust “probably carcinogenic to humans (Group 2A).” It appears that after Dr. Goldstein’s
testimony and report in 2011, IARC released a new study on June 12, 2012, which “classified
diesel engine exhaust as carcinogenic to humans (Group 1), based on sufficient evidence
that exposure is associated with an increased risk for lung cancer.” International Agency for
Research on Cancer, World Health Org., IARC:Diesel Engine Exhaust Carcinogenic,
(continued...)

50

Toxicology Program of the National Institutes of Environmental Health Science, and the

American Conference of Certified Industrial Hygienists. Based upon his review and analysis

of the literature on the subject, Dr. Goldstein opined that diesel exhaust can cause cancer in

general.

In determining whether diesel exhaust caused multiple myeloma, Dr. Goldstein

focused his research on the polycyclic aromatic hydrocarbon chemicals that are found in

diesel exhaust. After reviewing literature involving animal studies and the effects of

polycyclic aromatic hydrocarbons, Dr. Goldstein found that polycyclic aromatic hydrocarbon,

ingested through the lungs and carried through the bloodstream, can travel into bone marrow

and impact blood forming organs that are responsible for the development of multiple

myeloma. In other words, Dr. Goldstein opined that polycyclic aromatic hydrocarbons

caused multiple myeloma.29

28
(...continued)
http://www.iarc.fr/en/media-centre/pr/2012/pdfs/pr213_E.pdf (last visited on Nov. 8, 2013).
29
Dr. Goldstein made clear that no study that he reviewed stated definitively
that polycyclic aromatic hydrocarbons caused multiple myeloma. His opinion was based
upon the weight of the evidence.

51

 Dr. Goldstein’s report set out an analysis of the degree to which Mr. Harris was

exposed to diesel exhaust:30

In evaluating the risk posed to Mr. Harris by diesel
exhaust in his work environment it is important to get some idea
of the dose. Unfortunately no contemporaneous measures of
relevant contaminants were made in the time before his
diagnosis. . . . What I will therefore attempt to do is put the dose
ratio into perspective by using available data (including
anecdotal evidence) as well as guidelines for diesel exhaust
proposed by the American Conference of Governmental
Hygienists for a Threshold Value limit for diesel exhaust of
0.15mg/m3 (Time Weighted Average). It is intended to provide
a perspective of the conditions when a train was dragging a full
load uphill in an unvented tunnel.

For this calculation I assume that the engines on Mr.
Harris’ run were 3000 hp and met the exhaust standards of 0.6
g particulate matter and 1.0 g total hydrocarbons (PAH) per bhp­
hr for diesel engines manufactured between 1973 and 2001 (63
CFR 18997-19084, 16 Apr. 1998). Thus each locomotive in the
consist taking 10-20 minutes to pass through one of the longer
tunnels on the Allegheny and New River routes would have
produced 300-600 g of particulate matter. Using Stretcher’s
Neck for this example, the tunnel is 1588 feet long and the bore

30
Courts have

recognized that in toxic tort cases it is generally
difficult or impossible to quantify a plaintiff’s
exposure to a toxin[.] [Therefore], [i]t is not
always necessary for a plaintiff to quantify
exposure levels precisely or use the dose-response
relationship, provided that whatever methods an
expert uses to establish causation are generally
accepted in the scientific community.

Nonnon v. City of New York, 932 N.Y.S.2d 428, 436-37 (N.Y. App. Div. 2011).

52

 is 21' x 25 feet (estimated from photos of the tunnel), the tunnel
has a volume of 30878 cubic yards. For a roughly 10-20 minute
exposure the trainmen would have been in an environment of
9.7-19.5mg/yd3 of particulate matter, though the concentration
in the engine cab would likely be less. To put this in
perspective, the ACGLH proposed (subsequently withdrawn) a
threshold limit of value 0.5-0.15mg/m3 (one m3 and one yd3 are
essentially the same) time weighted average of particulate matter
for an 8 hour workday in its recommendation. Using the
0.15mg/m3 value, Mr. Harris found himself surrounded by an
environment that exceeded the proposed 8 hour average
concentration limit by 65-to-130-fold. . . .

....

It is my opinion that Mr. Harris through his employment
by CSX was exposed to high levels of diesel exhaust, an agent
determined by scientific and medical experts to be a probable or
likely human carcinogen. Absent other factors, it can be
reasonably concluded that this exposure was a major factor in
his multiple myeloma. The weight of scientific and medical
evidence from humans, animal studies, studies with tissues and
cells using diesel exhaust, closely related pyrogenic materials
and chemicals known to be in diesel exhaust supports this
conclusion as does an understanding of the conditions under
which Mr. Harris worked for 29 years.

3. Dr. Durie’s qualifications, methodology and opinion. Dr. Durie was

called as an expert witness by Petitioner. Dr. Durie received a medical degree in 1966 from

the University of Edinburgh Medical School, Edinburgh, Scotland. Dr. Durie has published

approximately 400 peer reviewed articles in scientific journals, the majority of which involve

multiple myeloma. He has been recognized as one of the top ten multiple myeloma

53

researchers in the world. Dr. Durie is board certified in internal medicine, hematology and

oncology.

From 1972-1992, Dr. Durie was on the faculty at the University of Arizona

College of Medicine. Dr. Durie was on the faculty at Charing Cross and Westminster

Medical School, University of London, from 1989-1992. From 1993 to the present, Dr.

Durie has been the Director of Hematologic Research and Myeloma Programs at

Cedars-Sinai Comprehensive Cancer Center at the University of California, Los Angeles

(“UCLA”). During his career, Dr. Durie has spent roughly thirty years doing laboratory

research involving multiple myeloma. Additionally, for many years, Dr. Durie prepared

summaries of every article that was published on multiple myeloma and presented the

material at the Annual Review of Medicine.

Dr. Durie was retained in this litigation to render an opinion as to whether

diesel exhaust caused multiple myeloma. Dr. Durie testified that he relied upon the Bradford

Hill methodology to render his opinion.

Dr. Durie reviewed reports by the Environmental Protection Agency,

International Agency for Research on Cancer, and National Toxicology Program of the

National Institutes of Environmental Health Science, which concluded that diesel exhaust

54

contained chemicals that were carcinogenic in humans, such as benzene and polycyclic

aromatic hydrocarbons. He consulted a report linking diesel exhaust with multiple myeloma

and epidemiologic literature concerning diesel exhaust and multiple myeloma. He reviewed

animal studies involving exposure to benzene, polycyclic aromatic hydrocarbons and

pristane. Dr. Durie reviewed the literature showing that benzene caused the loss of certain

chromosomes, and that Mr. Harris suffered the same chromosomal damage. Dr. Durie

testified that during his career, he has treated thousands of patients with multiple myeloma

and that when he asked “them what their job is, it is amazing how frequently they’ll say

they’re an engineer or that they’re working with chemicals. And so the occurrence of

occupations where there is a risk of exposure is remarkably frequent.”

Dr. Durie’s written report summarized his findings indicating the causal

relationship of diesel exhaust and multiple myeloma as follows:

[1] Martyn T. Smith and the group al-Berkley California
have detailed the chromosomal changes linked to human
benzene exposure. These chromosome changes include specific
findings in the bone marrow myeloma cells from Ronald
Harris. . . . Ronald Harris’s myeloma thus manifests a
chromosomal pattern characteristic of benzene exposure.

....

[2] The linage between diesel exhaust carcinogen
exposure and the development of multiple myeloma in the case
of Ronald Harris is thus both plausible and highly probable.

55

 [3] Of note the more likely than not association between
multiple myeloma and diesel exhaust exposure is supported by
the known presence of multiple other toxic compounds in the
exhaust [such as the] pristane chemical studied extensively by
Michael Potter since the 1960’s and known to [have] induced
plasmacytomata in mice (analogous to human multiple
myeloma). Recent studies at UCLA have shown that pristane
levels can be measured in vivo in humans and linked to immune
regulatory dysfunction with increased B-cell activation.
Myeloma is derived from abnormal B-lymphocytes. In addition,
diesel exhaust contained many of the same polycyclic aromatic
hydrocarbons found in coal tar and pitch blends both of which
are known human carcinogens. Heavy metals such as nickel are
also present with known carcinogenic potential. All this
reinforces the plausible and probable causative relationship
between diesel exhaust and the development of multiple
myeloma.

....

[4] I strongly support the fact that in the case of Ronald
Harris the workplace exposures at CSX Transportation Inc. were
more probably than not a causative factor in the development of
multiple myeloma.

4. Dr. Shields’ qualifications, methodology and opinion. Dr. Shields was

called as an expert witness by CSX. Dr. Shields received a medical degree in 1983 from

Mount Sinai School of Medicine, New York. Dr. Shields has published approximately 154

peer reviewed articles in scientific journals. Dr. Shields’ area of expertise includes

hematology and oncology. Dr. Shields is board certified in internal medicine and oncology.

56

 From 1984-1989, Dr. Shields worked as a civilian physician at three medical

facilities in Washington, D.C. Dr. Shields served as a commissioned officer in the United

States Public Health Service Commissioned Corps from 1990-199931 and ultimately attained

the rank of captain. From 2000 to the 2011, Dr. Shields was on the faculty at Georgetown

University Medical Center. From 2006-2008, Dr. Shields was the senior medical director

at Capital Breast Care Center in Washington, D.C. During the hearing in this case, Dr.

Shields testified that he was now employed with the Ohio State University Comprehensive

Cancer Center.

Dr. Shields was retained by CSX to render an opinion as to whether diesel

exhaust caused multiple myeloma. Dr. Shields testified that he relied upon the Bradford Hill

methodology to render his opinion.

Dr. Shields testified that he went on the internet to a website run by the

National Institute of Health and researched articles dealing with diesel exhaust and multiple

myeloma. Dr. Shields indicated that he reviewed twenty or more papers that involved

railroad workers and cancers. Dr. Shields testified that he “inferred” from this data that

31
Commissioned Corps officers serve in a variety of positions throughout the
United States Department of Health and Human Services and certain other federal agencies.
See United States Pub. Health Serv. Commissioned Corps, U.S. Dep’t. of Health & Human
Servs., http://www.usphs.gov/aboutus/mission.aspx (last visited on Nov. 8, 2013).

57

myeloma was not found in the studies because it was not mentioned. Specifically, Dr.

Shields stated that “if myeloma was going to arise from the way they’re describing Mr.

Harris’ exposure, these studies would show it.” Dr. Shields acknowledged that he was aware

of a study that showed a significant association between myeloma and railroad workers. Dr.

Shields discounted the study because, in his opinion, the study did not implicate diesel

exhaust as a cause for any of the cancers. Several other studies linking myeloma and diesel

exhaust were found not to be significant by Dr. Shields. Studies that showed an association

between benzene and myeloma were also rejected by Dr. Shields as not significant to

establish causation. Ultimately, Dr. Shields opined that, from his review of the literature,

“there’s no evidence or there’s insufficient evidence that railroad workers are at increased

risk of myeloma.” At the conclusion of Dr. Shields direct examination, counsel for CSX

asked the following question:

Q. Do you have an opinion as to whether the hypothesis
in this case that exposure to diesel exhaust causes multiple
myeloma has been proven?

A. Yes. It’s my opinion that it – that it’s not been proven.

5. Dr. Green’s qualifications, methodology and opinion. Dr. Green was

called as an expert witness by CSX. Dr. Green received a Ph.D. in food science and

technology from the Department of Nutrition and Food Science at Massachusetts Institute

of Technology in 1981. Dr. Green has published approximately 139 peer reviewed articles

58

in scientific journals. She is also the author of “In Search of Safety: Chemicals and Cancer

Risk” (Harvard University Press 1988). Dr. Green’s area of expertise is toxicology. Dr.

Green is a board certified toxicologist.

Dr. Green was a research director of Scientific Conflict Mapping Project at

Harvard University from 1983-1985. From 1985-1989, Dr. Green was employed at Meta

Systems, Inc., as vice president of Environmental Health and Toxicology. From 1989 to the

present, Dr. Green has been president of Cambridge Environmental, Inc.

Dr. Green was retained by CSX to render an opinion as to whether diesel

exhaust caused multiple myeloma. Dr. Green did not indicate any specific methodology that

she used to render her opinion. However, her testimony suggests she followed the Bradford

Hill methodology.

Dr. Green testified that she does not know of any literature linking any type of

cancer through the inhalation of pristane. Dr. Green also testified that neither the

Environmental Protection Agency’s Health Assessment Document for Diesel Engine Exhaust

nor the National Toxicology Program support the assertion that diesel exhaust causes

myeloma cancer. Dr. Green found a study of Swedish workers by Dr. Paolo Bofetta was

irrelevant, even though the study showed that over 800 workers exposed to diesel exhaust

59

contracted multiple myeloma. Dr. Green found the study was not significant because over

800 other men who were studied contracted multiple myeloma, but there was no evidence

that they also were exposed to diesel exhaust. Dr. Green opined that “diesel engine exhaust

might cause lung cancer, but there is no credible evidence that it causes multiple myeloma.”

H. The Circuit Court’s Orders Excluding the

Testimony of Petitioner’s Experts

We have no hesitancy in finding that the opinions of Petitioner’s three experts

regarding the causal link between diesel exhaust and multiple myeloma satisfy certain

requirements of Rule 702. Their opinions would “assist the trier of fact to understand the

evidence or to determine a fact in issue.” W. Va. R. Evid. 702. All three experts are

witnesses “qualified as an expert by knowledge, skill, experience, training, or education.”

Id. Additionally, the testimony of the experts was relevant to issues in the case. W. Va.

R. Evid. 402. Thus, the question before us is whether the trial court abused its discretion in

concluding that the reliability prong of Rule 702 was not met. That issue, properly framed,

is whether Petitioner’s three experts used reliable methodologies in rendering opinions on

the causation issue linking diesel exhaust with multiple myeloma. As we will explain, below,

the trial court’s analysis exceeded this narrow issue. Instead, the court in rendering its ruling,

addressed the jury question: Did Petitioner’s three experts prove causation? Because the

trial court exceeded the scope of its narrow review of the reliability prong of Rule 702, we

60

find it necessary to examine cases that have demonstrated the narrow focus used to make the

reliability determination.

To begin, the court in King v. Burlington Northern Santa Fe Railway Co., 762

N.W.2d 24 (Neb. 2009), provided an excellent analysis of the limited gatekeeper role of trial

courts. In King, the wife of a deceased former railroad employee brought an action seeking

damages against the railroad under the Federal Employers’ Liability Act.32 The plaintiff

alleged that her husband contracted multiple myeloma due to his exposure to diesel exhaust

fumes while working for the railroad as a brakeman. The defendant moved the court to

exclude the plaintiff’s expert. The opinion in King summed up the arguments and the trial

court’s ruling as follows:

Differing epidemiological studies supported the experts’
deposition testimony. [Plaintiff’s] expert, Dr. Arthur Frank,
blamed [decedent’s] multiple myeloma on his exposure to diesel
exhaust. Of course, [defendant’s] expert, Dr. Peter G. Shields,
disagreed. He believed that the causes were unknown and that
the majority of epidemiological studies failed to show that diesel
exhaust can cause multiple myeloma. The district court
sustained [defendant’s] motion to exclude Frank’s testimony,
concluding that it failed to pass muster under our
Daubert/Schafersman framework. It reasoned that his
methodology was unreliable because the studies he relied on
failed to conclusively state that exposure to diesel fuel exhaust
causes multiple myeloma.

32
The plaintiff’s husband was the original plaintiff, but he died during the
pendency of the litigation.

61

King, 762 N.W.2d at 31.

After the trial court excluded the plaintiff’s expert witness in King, it granted

summary judgment to the defendant. The plaintiff appealed to a Nebraska appellate court.

The appellate court affirmed. The plaintiff then appealed to Nebraska’s Supreme Court. The

high court in King reversed the ruling of the trial court after concluding that it applied an

improper standard for reviewing the admissibility of expert testimony. The opinion in King

outlined the following limited gatekeeper role of trial courts:

Here, the parties do not dispute Frank’s qualification to
give expert medical testimony or to interpret epidemiological
studies. We see the broad issue as whether under our
Daubert/Schafersman framework, Frank based his opinion on a
reliable, or scientifically valid, methodology. . . .

In determining the admissibility of an expert’s opinion,
the court must focus on the validity of the underlying principles
and methodology—not the conclusions that they generate. And
reasonable differences in scientific evaluation should not
exclude an expert witness’ opinion. The trial court’s role as the
evidentiary gatekeeper is not intended to replace the adversary
system but to ensure that an expert, whether basing testimony
upon professional studies or personal experience, employs in the
courtroom the same level of intellectual rigor that characterizes
the practice of an expert in the relevant field. In sum, while the
trial court acts as the evidentiary gatekeeper, it is not a
goalkeeper.

....

. . . Absent evidence that an expert’s testimony grows out
of the expert’s own prelitigation research or that an expert’s
research has been subjected to peer review, experts must show

62

 that they reached their opinions by following an accepted
scientific method or procedure as it is practiced by others in
their field.

Epidemiological statistical techniques for testing a
causation theory have been subject to peer review and are
generally accepted in the scientific community. The studies
Frank relied upon were subject to peer review, and the
researchers did not develop the statistical techniques used in the
studies for this litigation. . . . Accordingly, the district court
needed to consider only two issues regarding Frank’s opinion on
. . . causation. Were the results of the epidemiological studies
Frank relied on sufficient to support his opinion regarding . . .
causation? And did he review the scientific literature or data in
a reliable manner? In other words, did too great an analytical
gap exist between the data and Frank’s opinion?

....

We believe the district court erred in concluding that
Frank’s causation opinion was unreliable because Frank could
not point to a study that concludes exposure to diesel exhaust
causes multiple myeloma. As explained, individual
epidemiological studies need not draw definitive conclusions on
causation before experts can conclude that an agent can cause a
disease. If the expert’s methodology appears otherwise
consistent with the standards set out above, the court should
admit the expert’s opinion. But here, the court did not inquire
into Frank’s methodology.

King, 762 N.W.2d at 42-49 (internal quotations and citations omitted).

Another case, though it did not involve multiple myeloma, which illustrates a

trial court’s limited gatekeeper role is Milward v. Acuity Specialty Products Group, Inc., 639

F.3d 11 (1st Cir. 2011). In Milward, the plaintiffs, husband and wife, filed an action against

63

manufacturers of products used in refrigerators. The plaintiff husband worked as a

refrigeration technician. The plaintiffs alleged that the husband contracted acute

promyelocytic leukemia (“APL”) as a result of exposure to benzene that was contained in the

defendants’ products. The trial court held a four day hearing to determine whether plaintiff’s

expert on causation would be allowed to testify that benzene caused APL. The trial court,

“in a detailed opinion, ruled that ‘Dr. Smith’s proffered testimony that exposure to benzene

can cause APL lacks sufficient demonstrated scientific reliability to warrant its admission

under Rule 702.’” Milward, 639 F.3d at 13. The trial court thereafter dismissed the action.

The First Circuit Court of Appeals reversed after concluding that the trial court exceeded its

discretion in finding that the opinion of plaintiffs’ expert was wrong. The First Circuit

outlined the limited role of the trial court in deciding the admissibility of expert testimony:

[T]rial courts are [not] empowered to determine which of
several competing scientific theories has the best provenance.
Daubert does not require that a party who proffers expert
testimony carry the burden of proving to the judge that the
expert’s assessment of the situation is correct. The proponent of
the evidence must show only that the expert’s conclusion has
been arrived at in a scientifically sound and methodologically
reliable fashion. The object of Daubert is to make certain that
an expert, whether basing testimony on professional studies or
personal experience, employs in the courtroom the same level of
intellectual rigor that characterizes the practice of an expert in
the relevant field.

So long as an expert’s scientific testimony rests upon
good grounds, based on what is known, it should be tested by
the adversarial process, rather than excluded for fear that jurors
will not be able to handle the scientific complexities. Vigorous
cross-examination, presentation of contrary evidence, and

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careful instruction on the burden of proof are the traditional and
appropriate means of attacking shaky but admissible evidence.

....

. . . [T]he alleged flaws identified by the court go to the
weight of Dr. Smith’s opinion, not its admissibility. There is an
important difference between what is unreliable support and
what a trier of fact may conclude is insufficient support for an
expert’s conclusion.

The court’s analysis repeatedly challenged the factual
underpinnings of Dr. Smith’s opinion, and took sides on
questions that are currently the focus of extensive scientific
research and debate—and on which reasonable scientists can
clearly disagree. In this, the court overstepped the authorized
bounds of its role as gatekeeper. The soundness of the factual
underpinnings of the expert’s analysis and the correctness of the
expert’s conclusions based on that analysis are factual matters
to be determined by the trier of fact. When the factual
underpinning of an expert’s opinion is weak, it is a matter
affecting the weight and credibility of the testimony—a question
to be resolved by the jury.

....

. . . The sum of Dr. Smith’s testimony was not merely that
it is possible, or even biologically plausible, that benzene causes
APL. Rather, the sum of his testimony was that a weighing of
the Hill factors, including biological plausibility, supported the
inference that the association between benzene exposure and
APL is genuine and causal.

The record clearly demonstrates that Dr. Smith’s opinion
was based on an analysis in which he employed the same level
of intellectual rigor that he employs in his academic work. In
excluding Dr. Smith’s testimony, the district court did not
properly apply Daubert and exceeded the scope of its discretion.
We reverse the district court’s judgment for the defendants and

65

 its exclusion of Dr. Smith’s testimony, and we remand for
proceedings consistent with this opinion.

Milward, 639 F.3d at 15-26 (internal quotations and citations omitted)..

In Wagoner v. Exxon Mobil Corp., 813 F. Supp. 2d 771 (E.D. La. 2011), the

plaintiff, widow and legal representative of decedent, filed a products liability action against

manufacturers of benzene-containing products alleging that, as a result of the decedent’s

exposure to benzene, the decedent contracted and died of multiple myeloma. The defendants

filed motions to exclude plaintiff’s two causation experts. The basis of the motions, and the

district court’s rejection of the same, were addressed by the court as follows:

Defendants have raised five arguments with regard to the
reliability of the testimony of Dr. Butler and Dr. Saux . . . : 1)
their opinion rests on studies that do not show statistically
significant findings; 2) their opinion relies on studies that do not
examine benzene specifically; 3) their opinion rests on studies
that are not published in peer-reviewed journals and are
otherwise flawed; 4) their opinion reflects an incomplete review
of the relevant literature; and 5) their opinion fails to articulate
a biologically plausible mechanism for benzene to cause
[multiple myeloma] and thus does not meet the Bradford Hill
criteria.

....

None of the arguments raised by Defendants in support
of their motions to exclude Dr. Butler and Dr. Saux are
persuasive. The two individuals are qualified to render an
opinion . . ., and at least two studies support the notion that there
is a statistically significant association between benzene and
[multiple myeloma]. The fact that those studies may be flawed,
that there are studies that cut against the two doctors’ opinion,

66

 and that the doctors could not articulate a biologically plausible
mechanism for benzene to cause [multiple myeloma] all go to
the weight of their opinion, and not the question of
admissibility. . . . Accordingly, the motions to exclude and for
summary judgment must be denied.

Wagoner, 813 F. Supp. 2d at 800-05.

Finally, in Moreland v. Eagle Picher Technologies, 362 S.W.3d 491

(Mo. Ct. App. 2012), a Missouri appellate court addressed the admissibility of an expert

opinion under its rules of evidence in the context of a workers’ compensation claim. The

employee in Moreland alleged that he developed multiple myeloma as a result of years of

inhalation of chemicals from plastics that his employer produced. The chemicals in the

plastics included benzene, trichloroethylene, cadmium, nickel, and platinum. The employee

produced an expert witness at the administrative level who testified that his exposure to

benzene caused him to develop multiple myeloma. The employer called an expert witness

who opined that benzene had never been proven to cause multiple myeloma. The ALJ found

in favor of the employee and awarded him workers’ compensation benefits. An appellate

court affirmed the award. In doing so, the appellate court in Moreland set out the following

relevant discussion regarding the employee’s causation expert:

Dr. Bernard Goldstein (“Dr. Goldstein”), a professor of
medicine at the University of Pittsburg [sic] Graduate School of
Public Health and School of Medicine, and also a physician,
toxicologist, and hematologist, testified on behalf of Moreland.
Dr. Goldstein testified he had studied benzene toxicity and
published close to one hundred papers or reviews upon the

67

subject since the 1960s. Dr. Goldstein also specifically
published and instructed members of the federal judiciary on
issues concerning toxicology and, in particular, the issue of
causation and whether chemical agents should be deemed to
have caused or contributed to the development of multiple
myeloma.

Dr. Goldstein testified that benzene was reasonably
probable to be a cause of multiple myeloma based upon
epidemiological data, bioassays (experiments on laboratory
animals), and mechanistic data. Dr. Goldstein testified that
these sources of information are recognized by the International
Agency for Research on Cancer and could be applied to
substantiate that benzene caused multiple myeloma. . . .

....

Dr. Goldstein testified that multiple myeloma is an
identifiable disease and it is reasonably probable that exposure
to benzene, either by air or dermal absorption, or both, is a
substantial factor to cause the compounding of cells that lead
[sic] to multiple myeloma.

....

Here, [the employer] specifically argues only that Dr.
Goldstein’s opinion is not based on medical certainty, and is not
based on any medical or scientific facts that are reasonably
relied upon by experts in the field of medical expertise.
However, . . . Dr. Goldstein extensively explained many of the
studies which show causation between benzene and multiple
myeloma. Further, Dr. Goldstein testified that these sources of
information are recognized by the International Agency for
Research on Cancer and could be applied to substantiate that
benzene causes multiple myeloma. Thus, the facts and data on
which Dr. Goldstein based his opinions are a type reasonably
relied on by experts in the field.

68

 Accordingly, the Commission’s finding that Dr.
Goldstein’s testimony meets the standard required of expert
testimony was supported by competent and substantial evidence.

Moreland, 362 S.W.3d at 500-04 (internal citations omitted).33

33
In the context of an administrative workers’ compensation claim, this Court
addressed the issue of the reliability of evidence showing a link between benzene exposure
and a cancer called chronic myelogenous leukemia. In Casdorph v. West Virginia Office
Insurance Commissioner, 225 W. Va. 94, 690 S.E.2d 102 (2009), the claimant worked as an
auto mechanic for the State Police for nearly twenty-two years. After the claimant was
diagnosed with chronic myelogenous leukemia, he filed a claim for workers’ compensation
benefits. (The claimant died while the case was pending at the administrative level). The
claimant alleged that his cancer was caused by his exposure to benzene in the workplace.
During a hearing before an ALJ the claimant provided evidence from several experts,
including Dr. Infante, who testified that claimant “had ample opportunity for occupational
exposure to benzene and other solvents contaminated with benzene due to his occupation and
stated that benzene is the cause of leukemia and CML is a type of leukemia associated with
benzene exposure.” Casdorph, 225 W. Va. at 102, 690 S.E.2d at 110. The ALJ found that
the claimant developed chronic myelogenous leukemia from his exposure to benzene and
therefore ruled the claim was compensable. The Board of Review reversed the decision of
the ALJ. On appeal, this Court reinstated the ALJ’s decision. We concluded as follows:

The medical literature and expert and fact witness
testimony in this case sufficiently established that a causal link
between the Appellant’s benzene exposure and CML existed.
Although the Appellees assert that the case studies cited by
Appellant showing a causal connection between benzene
exposure and CML have not been able to get peer reviewed
textbooks to acknowledge and print them as common or
accepted consensus medical opinion, we find that these case
studies, although small, are valid studies that have been peer
reviewed and published. We acknowledge, as Appellees
contend, that this Court recognized in State v. Leep, 212 W. Va.
57, 569 S.E.2d 133 (2002) that “whether a scientific theory is
generally accepted within a scientific community” is a factor
that must be weighed in determining whether to allow such
testimony as evidence. However, we must also be reminded that
(continued...)

69

 The foregoing authorities consistently demonstrate the narrow scope of a trial

court’s consideration of the admissibility of scientific expert testimony: [a] narrow focus that

our cases have acknowledged, but which far too often has been misunderstood. Therefore,

we believe it is necessary to carefully and clearly articulate our standard for reviewing the

reliability prong of the admission of scientific expert testimony. Thus, we make clear, and

so hold that, when a trial court is called upon to determine the admissibility of scientific

expert testimony, in deciding the “reliability” prong of admissibility the focus of the trial

court’s inquiry is limited to determining whether the expert employed a methodology that is

recognized in the scientific community for rendering an opinion on the subject under

consideration. If the methodology is recognized in the scientific community, the court should

then determine whether the expert correctly applied the methodology to render his or her

opinion. If these two factors are satisfied, and the testimony has been found to be relevant,

and the expert is qualified, the expert may testify at trial.

33
(...continued)

the Rules of Civil Procedure and the Rules of Evidence do not

strictly apply to workers’ compensation claims.

Casdorph, 225 W. Va. at 104-05, 690 S.E.2d at 112-13 (footnote added). It is important to
note that the decision in Casdorph made clear that it was not evaluating the admissibility of
the expert testimony under the standards of the rules of evidence, because those rules did not
strictly apply to workers’ compensation litigation. Casdorph is distinguishable from
Moreland in that regard because Missouri applies its rules of evidence to workers’
compensation litigation.

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 We wish to clarify that the standards outlined above are not new principles

under this Court’s Daubert/Wilt jurisprudence. These principles have always been an

implicit part of the Daubert/Wilt analysis. Simply put, however, these principles have not

been clearly understood or followed by trial courts. For instance, this Court made the

following observations in Wilt:

We . . . are of the view that, under Rule 702, there is a
category of expert testimony based on scientific methodology
that is so longstanding and generally recognized that it may be
judicially noticed, and, therefore, a trial court need not ascertain
the basis for its reliability.

Thus, we believe that Daubert is directed at situations
where the scientific or technical basis for the expert testimony
cannot be judicially noticed and a hearing must be held to
determine its reliability.

Wilt, 191 W. Va. at 46, 443 S.E.2d at 203. This limitation recognized in Wilt has been lost

in practice. Litigants invariably have crowded trial court calendars with purported

Daubert/Wilt evidentiary hearings whenever an expert is called to testify. This was never the

intent of our Daubert/Wilt analysis.

In Gentry v. Mangum, 195 W. Va. 512, 466 S.E.2d 171 (1995), Justice

Cleckley attempted to clarify how Daubert/Wilt was to be applied by “giv[ing] circuit courts

more guidance from a procedural standpoint in resolving scientific evidence issues.”

Gentry, 195 W. Va. at 521, 466 S.E.2d at 180. Gentry pointed out in crystal clear terms that,

71

 [a]ctually, most scientific validity issues will be resolved
under judicial notice pursuant to Rule 201. Indeed, most of the
cases in which expert testimony is offered involve only qualified
experts disagreeing about the interpretation of data that was
obtained through standard methodologies. Daubert/Wilt is
unlikely to impact upon those cases. Therefore, circuit courts
are right to admit or exclude evidence without “reinventing the
wheel” every time by requiring parties to put on full proof of the
validity or invalidity of scientific principles. Where judicial
notice is appropriate, the circuit court should use it.

Gentry, 195 W. Va. at 522, 466 S.E.2d at 181. In Syllabus point 4 of Gentry, Justice

Cleckley simplified and reformulated our Daubert/Wilt standard as follows:

When scientific evidence is proffered, a circuit court in
its “gatekeeper” role under Daubert v. Merrell Dow
Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125
L. Ed. 2d 469 (1993), and Wilt v. Buracker, 191 W. Va. 39, 443
S.E.2d 196 (1993), cert denied, 511 U.S. 1129, 114 S. Ct. 2137,
128 L. Ed. 2d 867 (1994), must engage in a two part analysis in
regard to the expert testimony. First, the circuit court must
determine whether the expert testimony reflects scientific
knowledge, whether the findings are derived by scientific
method, and whether the work product amounts to good science.
Second, the circuit court must ensure that the scientific
testimony is relevant to the task at hand.

195 W. Va. 512, 466 S.E.2d 171.

Gentry attempted to show that a full blown evedentiary Daubert/Wilt analysis

was required only for evaluating a new and/or novel scientific methodology. Recognized

methodologies are the subject of judicial notice. Moreover, this Court explained in Syllabus

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point four of Mayhorn v. Logan Medical Foundation, 193 W. Va. 42, 454 S.E.2d 87 (1994),

that

[p]ursuant to West Virginia Rules of Evidence 702 an
expert’s opinion is admissible if the basic methodology
employed by the expert in arriving at his opinion is scientifically
or technically valid and properly applied. The jury, and not the
trial judge, determines the weight to be given to the expert’s
opinion.

See 2 Franklin D. Cleckley, Louis J. Palmer, Jr. and Robin Jean Davis, Handbook on

Evidence for West Virginia Lawyers § 702.02[2][c] (5th ed. 2012) (“The [Daubert/Wilt]

regime contemplates that trial judges will perform a gatekeeping function, determining

whether the . . . methodology underlying proffered expert testimony is scientifically valid and

whether that . . . methodology properly can be applied to the facts in issue.”). We note that

we are not alone in limiting an evidentiary hearing to determine the reliability of experiments

conducted for litigation and/or novel scientific methodology. See Nonnon v. City of New

York, 932 N.Y.S.2d 428, 429 (N.Y. App. Div. 2011) (“[W]e [have] determined that

plaintiffs’ expert evidence did not require that a hearing be held [because] neither the

deductions of the expert epidemiologists and toxicologists, nor the methodologies employed

by them, in reaching their conclusions are premised on . . . novel science[.]” (internal

quotations and citations omitted)). The court in Nonnon observed that

epidemiology and toxicology are hardly novel sciences, but
rather, well-established and accepted methodologies. In such a
case, the focus moves from the general reliability concerns . . .
to the specific reliability of the procedures followed to generate

73

 the evidence proffered and whether they establish a foundation
for the reception of the evidence at trial.

Nonnon, 932 N.Y.S.2d at 435.

In the instant case, the trial court erred by holding a mini-trial to set out and

resolve issues that were purely matters for jury consideration.34 The three orders excluding

Petitioner’s three experts set out and resolved an array of disputed factual matters that were

exclusively grist for the jury and which had no relevancy to the limited role the trial court had

under the facts of this case. For instance, as noted by Petitioner, the orders found:

1. If a difference between a case group and control group
is not statistically significant then there is no difference at all.

2. It is acceptable scientific practice to interpret as “not
different” a study that shows an elevated risk that is not
statistically significant.

3. There is substantially more benzene in cigarette smoke
than diesel exhaust.

4. Benzene is present only in trivial doses in diesel
exhaust.

5. The hypothesis that diesel exhaust causes multiple
myeloma is confounded by the fact that cigarette smoking does
not.

34
This Court is fully aware that litigants have abused the limited resources of
our trial judges by demanding full-blown evidentiary hearings in most cases where expert
testimony is offered. This opinion is intended to make unequivocally clear that the
admissibility principles under Daubert/Wilt were never intended to allow the abuse that has
become routine in our trial courts.

74

 6. Most epidemiologic studies must be positive for
purported causal association to be real.

7. Of forty-seven (47) studies of diesel exposed workers
only eight (8) purport to be positive.

9. The epidemiologic literature investigating a causal
association between railroad employment and multiple myeloma
is null and not supportive of the subject hypothesis.

10. There are approximately ten (10) published studies
investigating [sic] causal link between benzene and multiple
myeloma. None of them are positive.

11. The epidemiologic literature regarding PAH exposure
and multiple myeloma does not support the subject hypothesis.

12. IARC Technical Publication 42 was not intended to
make a causation statement but to express a research agenda.

13. The general causation hypothesis that exposure to
diesel exhaust causes multiple myeloma has not been proven.

Clearly, the above findings made by the trial court should never have been

considered as part of its limited gatekeeper role in this case. All of the above findings

involve disputed opinions between the experts. They have nothing to do with the reliability

of the methodologies used by the Petitioner’s experts. In fact, the trial court could have

resolved the question of the relevancy and reliability of Petitioner’s experts through

arguments by the parties and without their experts’ testimony. It is undisputed that the

methodologies employed by Petitioner’s experts are recognized in the scientific community.

Ironically, CSX’s experts relied upon the same methodologies. There is also no reasonable

75

dispute that Petitioner’s three experts employed the methodologies in a manner consistent

with how they are employed in the scientific community. The only issue that was in dispute

was whether Petitioner’s experts were correct in reaching the conclusions they reached.

Challenging the latter issue is a matter for jury determination.35

We understand there will be cases where a party seeks to offer a new and novel

methodology to explain causation, or where a party’s expert performed a specific experiment

for trial to show causation. In either of those situations, the rigorous prong of the

Daubert/Wilt gatekeeper analysis is implicated. In stark contrast, the experts in the instant

case did not offer new or novel methodologies. The epidemiological, toxicological, weight

of the evidence and Bradford Hill methodologies they used are recognized and highly

respected in the scientific community. And, as is detailed in this opinion, those experts

applied the methodologies consistently with the “level of intellectual rigor that characterizes

the practice of an expert in the relevant field.” Milward, 639 F.3d at 15.

35
This Court is aware that some courts have excluded expert testimony on the
issue of whether multiple myeloma is caused by diesel exhaust. See Aurand v. Norfolk S. Ry.
Co., 802 F. Supp. 2d 950 (N.D. Ind. 2011) (excluding plaintiff experts on multiple myeloma);
Morin v. United States, 534 F. Supp. 2d 1179 (D. Nev. 2005) (same); Castellow v. Chevron
USA, 97 F. Supp. 2d 780 (S.D. Tex. 2000) (same); Estate of Mitchell v. Gencorp, Inc., 968
F. Supp. 592 (D. Kan. 1997) (same); Sutera v. Perrier Grp. of Am. Inc., 986 F. Supp. 655
(D. Mass. 1997) (same); Richardson v. Union Pac. R.R. Co., 386 S.W.3d 77 (Ark . Ct. App.
2011) (same); Missouri Pac. R.R. Co. v. Navarro, 90 S.W.3d 747 (Tex. Ct. App. 2002)
(same). The decisions of the courts in those cases are inconsistent with the standards of
admissibility of scientific expert testimony that are followed in this jurisdiction.

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 IV.

CONCLUSION

We reverse the circuit court’s orders excluding the testimony of Petitioner’s

three experts. Furthermore, we reverse the order granting summary judgment in favor of

CSX. Finally, this case is remanded for further proceedings consistent with this opinion.

Reversed and Remanded.

77