IN THE SUPREME COURT OF TENNESSEE
AT NASHVILLE
FOR PUBLICATION
Filed: September 29, 1997
KENNETH McDANIEL, )
)
Plaintiff-Appellee, ) DAVIDSON CIRCUIT
)
)
Vs. ) HON. MARIETTA M. SHIPLEY,
) JUDGE
)
CSX TRANSPORTATION, INC., )
)
Defendant-Appellant. ) No. 01-S-01-9605-CV-00095
FILED
September 29, 1997
For Appellant: For Appellee:
Cecil W. Crowson
Wayne L. Robbins, Jr. Van Kirk McCombs, IIAppellate Court Clerk
Gareth S. Aden James H. Wettermark
GULLETT, SANFORD, BURGE & WETTERMARK, P.C.
ROBINSON & MARTIN, PLLC 2300 SouthTrust Tower
Nashville, Tennessee 37219 Birmingham, Alabama 35203-3204
Edward H. Stopher
BOEHL, STOPHER & GRAVES
Suite 2300, Providian Center
400 West Market Street
Louisville, Kentucky 40202-3346
OPINION
AFFIRMED. ANDERSON, C. J.
We granted this interlocutory appeal to clarify the standards for the
admissibility of scientific evidence under Tennessee Rules of Evidence 702 and
703.
The trial court, after a Tenn. R. Evid. 104 pretrial evidentiary hearing,
admitted into evidence the testimony of plaintiffs’ experts who relied on
epidemiological studies to prove that exposure to organic solvents caused a form
of brain damage known as toxic encephalopathy. The trial court found that this
scientific evidence would substantially assist the trier of fact and was reliable and
trustworthy.
The Court of Appeals denied an interlocutory appeal. We, however,
granted the interlocutory appeal and conclude that Tennessee Rules of Evidence
702 and 703 impose a duty upon trial courts to determine whether scientific
evidence will substantially aid the trier of fact and whether the underlying facts
and data relied on by the expert witness indicate a lack of trustworthiness. The
trial court must further determine whether the reasoning or methodology
underlying the scientific evidence is sufficiently valid and reliable, and whether it
can properly be applied to the facts at issue.
In making this determination, the trial court should focus on the principles
and methodology underlying the science, and not on the conclusions of experts.
The trial court is not required to determine that the principles and methodology
employed are generally accepted by the scientific community. The court needs
only to determine that the principles and methodology are scientifically valid and
reliable.
When these standards are applied in this case, the scientific evidence
proffered by the plaintiffs should be admitted. Accordingly, we conclude that the
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trial court did not abuse its discretion in denying the defendant’s motion in limine
which sought to exclude the plaintiffs’ expert testimony.
BACKGROUND
This case involves eighty-four (84) cases filed pursuant to the Federal
Employers Liability Act, 45 U.S.C. § 51, et seq., by employees of the defendant
CSX Transportation, Inc. (“CSXT”), a railroad operator, which were consolidated
for motions and case management in the Davidson County Circuit Court. Each
plaintiff alleges that he has suffered brain damage due to chronic exposure to
four (4) particular organic solvents1 while working in the CSXT mechanical shops
in Nashville, Tennessee.
The plaintiffs intend to rely upon occupational physicians to show that
long-term, low dosage exposure to the solvents has caused a form of brain
damage known as toxic encephalopathy, which is marked by diminished short-
term memory, sleeplessness, depression and anxiety. The plaintiffs’ experts rely
upon epidemiological studies, 2 which they contend established the causation
between long term exposure to solvents and damage to the central nervous
system.
1
The particular solvents at issue in this case are: trichloroethane, trichloroethylene,
perchlo roethylene , and m ineral spirits.
2
Epidemiology is the “study of the distribution and determinants of health-related states
and events in populations and the application of this study to control of health problems.”
Reference Manual on Scientific Evidence, Federal Judicial Center, p. 174 (1994)(hereinafter
“Reference Manual”).
There are two g eneral type s of epide miolog ical studies which ar e used to test a
hypothesis: (1) cohort studies and (2) case-control studies. In a cohort study, the epidemiologist
identifies a group of individuals who have been exposed to the chemical and another group of
individuals who have not been exposed to the chemical. The epidemiologist chooses two groups
as nearly identical as possible except for exposure to the chemical. The incidence rates of
disease of the exposed and non-exposed groups over a period of time is then observed. A case-
control study involves persons who either have the disease (cases) or do not have the disease
(controls ). The c ases a nd con trols are m atched for com parison . A determ ination is m ade as to
whethe r the individua ls in the cas e and c ontrol grou ps were expos ed to the c hem ical.
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CSXT sought to exclude the plaintiffs’ experts on the basis that their
testimony was without sufficient scientific support. CSXT contended that the
epidemiological studies relied on by the plaintiffs did not consistently establish a
causal connection with a relative risk or odds ratio that shows a statistically
significant degree of reliability. 3 It concluded, therefore, that the proffered expert
testimony on the issue would not “substantially assist” the trier of fact, and that
the facts and data underlying the testimony shows a “lack of trustworthiness.”
At a pretrial Tenn. R. Evid. 104 evidentiary hearing, several expert
witnesses for the plaintiff and the defendant offered their opinions concerning the
effect of long-term exposure to low doses of the organic solvents involved in this
litigation. The proof indicated that the solvents belong to a family of organic
solvents known as chlorinated hydrocarbons, while mineral spirits are generally
distilled from petroleum products. The industrial utility of the solvents lies in their
ability to dissolve grease.
The experts agreed that there is no objective diagnostic tool, (such as an
MRI, CT Scan, or X-Ray), that will support a diagnosis of toxic encephalopathy,
and that no biological mechanism has been identified that demonstrates how
exposure to the solvents causes the damage. Moreover, while the experts
agreed that acute exposure to high concentrations of the solvents can create
dizziness, disorientation, and even unconsciousness, the allegations in this case
involve exposure below the level necessary to render a person unconscious.
3
After collec ting the data either using a coho rt or case -control s tudy, epidem iologists
typica lly me asu re ris k us ing th e con cep ts of “ relativ e risk ” and /or “o dds ratio.” Coh ort stu dies yield
a direct measure of the risk of brain damage according to the presence or absence of solvent
exp osu re. T his dir ect m eas ure, k now n as t he re lative r isk, is the ra tio of th e incid enc e of b rain
damage or “toxic encephalopathy’ in the exposed group divided by the rate in the nonexposed
grou p. If the relativ e risk is 1.0 , then there is no a sso ciatio n bet wee n solv ent e xpo sure and b rain
damage. A relative risk of 4.0 indicates that the risk of disease in the exposed group is four times
higher tha n the risk of diseas e in the une xpose d group . Reference Manual at 148. By co ntrast,
case-control studies utilize an odds ratio in calculating risk. An odds ratio is based on a
comparison of the odds of having a disease when exposed to a suspected agent and when not
expos ed. Reference Manual at 149. Relative risk and odds ratio are generally similar in most
cases .
-4-
One of the plaintiffs’ experts, Dr. Edward Baker, a physician specializing in
occupational medicine with two masters degrees, one in public health and
another in epidemiology, testified that he has authored twenty-six articles and
four textbook chapters on the subject of the effects of exposure to solvents. He
began studying the effects of solvent exposure on the central nervous system
while on the faculty of Harvard University’s School of Public Health. He has
summarized epidemiological studies conducted since 1985 and has concluded
that “these cross sectional studies, viewed in the aggregate, support the view
that chronic solvent exposure causes impairment of neurobehavioral function.”
Baker, “A Review of Recent Research on Health Effects of Human Occupational
Exposure to Organic Solvents,” Journal of Occupational Medicine, Vol. 36, No.
10 (Oct. 1994).4 Baker testified that dose/response and degree of exposure
were critical to the causation inquiry.
Another plaintiffs’ expert, Dr. Douglas Linz, also a physician specializing in
occupational medicine, has authored four articles on the effects of exposure to
solvents and has diagnosed patients with chronic encephalopathy. Like Baker,
he has performed and reviewed the epidemiological studies on the subject and
has concluded that “chronic low dose exposure to solvents can cause chronic
encephalopathy.” Dr. Howard Frumkin, a physician with a doctorate in public
health, has evaluated patients for solvent exposure, and has researched and
written on the effects of exposure on the central nervous system. He testified
that a sufficient degree of exposure over a sufficient amount of time can cause
toxic encephalopathy, and that the diagnosis of chronic encephalopathy from low
4
Baker’s report studied among others, Hanninen (1991 & 1979); Baker (1988); Arlien-
Soberg (1979); Elofsson (19 80); Hane (1977); Bleeker (19 91); Bolla (1990); Parkinson (1990);
Maizlsih (1985); and Spurgeon (1992 ).
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dose exposure to solvents is generally accepted throughout the United States
and the world.5
In contrast, Dr. Philip Edelman testified on behalf of the defendant that
although dose response is critical to any toxicology study, “most” in the medical
community of toxicologists did not accept the causal connection between low
dose exposure to solvents and encephalopathy. Edelman, a physician who is
board certified in toxicology and occupational/environmental medicine, criticized
the epidemiological studies that the plaintiffs’ experts relied upon for lacking a
good dose/response relationship and for failing to control for confounding factors
such as age, intelligence, and the use of alcohol. Likewise, Dr. Joseph
McLaughlin, a Ph.D. in epidemiology, testified that the epidemiological studies on
the relation between exposure to solvents and toxic encephalopathy failed to
account for significant confounding factors. Finally, Dr. Robert James, a Ph.D. in
pharmacology, testified that he reviewed forty-five cross sectional studies and
determined that 84 percent supported the hypothesis and 16 percent did not. He
criticized the “positive” studies, however, for failing to account for the factors of
age, intelligence, experience, and alcohol consumption. In James’s opinion, the
diagnosis of toxic encephalopathy from exposure to solvents was not generally
accepted in the medical community.
After considering the testimony of the experts and analyzing the pertinent
studies, the trial court concluded that the proposed evidence was “grounded in
scientific theory,” was “generally accepted in the occupational health
community,” and was trustworthy and reliable. Although denying the defendant’s
motion to exclude the expert testimony, the trial court recognized the need to
develop a uniform and consistent body of law and granted the defendant’s
5
The plaintiffs’ fourth expert, Dr. Michael Kelly, was the examining physician who
diagnosed the plaintiffs’ toxic encephalopathy. He described the “differential diagnosis” procedure
he used in this regard.
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motion for an interlocutory appeal pursuant to Tenn. R. App. P. 9. Although the
Court of Appeals denied the interlocutory appeal, we granted the appeal to clarify
the standards for determining the admissibility of scientific evidence in this
jurisdiction. We now affirm the trial court.
SCIENTIFIC LITERATURE
We begin our analysis by reviewing the relevant material that was
submitted to the trial court and discussed by several of the experts during the
evidentiary hearing. In the 1970's, researchers in certain Scandinavian
countries, performing epidemiological studies using case report and cross-
sectional methods, 6 reported that neuropsychiatric symptoms may be induced by
long-term exposure to solvents. In 1979, the Danish physician, Arlien-Soborg,
coined the phrase “chronic painters’ syndrome,” in a study done on seventy
house painters. The report concluded that the majority of the painters who had
been exposed to organic solvents, often through a period with acute intoxication
symptoms, had gradually developed signs of a chronic brain syndrome. The
symptoms included impaired memory, fatigue, personality change, headaches,
and irritability. Arlien-Soborg, et al., “Chronic Painters’ Syndrome - Chronic Toxic
Encephalopathy in House Painters,” Acta. Neurol. Scand, 60:149-156 (1979).
Other authors, including plaintiffs’ expert Dr. Edward Baker, have reported that
the Scandinavian studies supported the hypothesis that toxic encephalopathy
occurs in individuals heavily exposed to solvents over a period of months to
6
Cross-sectional studies involve selection of individuals, regardless of exposure or
disease status. Subjects for such studies are chosen either at random or via probability sampling
procedures, which allows for the exam ination of the prevalence of a disease in a representative
sample of the popu lation. McCunney, “Epidemiology and Biostatics,” A Prac tical Appro ach to
Occupational and Environmental Medicine (2nd Ed.),” at 349 . Case reports are not
epidemiological studies, but merely reports of individuals who have been exposed to an agent and
then report symptoms associated with the disease. Case reports usually precede the institution
of formal epidemiological research, although they can be important in determining whether an
association exists between an agent and a disease or defect. For example, the medical
community became aware of the association between the drug, Thalidomide, used by pregnant
women as a sedative and birth defects in their children as a result of case reports.
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years. See Baker, et al., “The Neurotoxicity of Industrial Solvents: A Review of
the Literature, “ Am. J. of Indus. Med., 8:207-217 (1985). 7
As the defendant contends, the Scandinavian studies have been criticized
for failing to prove that the painters’ symptoms were related to their occupational
exposure to organic solvents and for the disappearance of evidence of
impairment in twenty re-examined workers. See Errebo-Knudsen and Olsen,
“Organic Solvents and Presenile Dementia (The Painters’ Syndrome): A Critical
Review of the Danish Literature,” The Sci. of the Total Env’t, 48:45-67(1986);
Gade et al., “Chronic Painter’s Syndrome. A Reanalysis of Psychological Test
Data in a Group of Diagnosed Cases,” Acta Neurol. Scand., 77:293-306 (1988).
Some studies have likewise questioned the Scandinavian studies. As one
report indicates:
Studies outside Scandinavia, mainly cross-sectional clinical
studies, have not supplied convincing evidence to support the
hypothesis of solvent exposure causing irreversible brain damage
. . . . The reason for this discrepancy might lie in differences of
study design, incomparable study populations, insufficient
adjustment for confounding factors, and, perhaps most importantly,
differences in disease classification.
Rasmussen et al., “Solvent-Induced Chronic Toxic Encephalopathy,” Am. J. Of
Indust. Med., 23:779-792 (1993); see also Williamson, et al., “A Prospective
Cohort Study of the Chronic Effects of Solvent Exposure,” Environmental Res.,
62:256-271 (1993)(“cross sectional studies suffer from problems of possible
confounding by a range of unknown factors and also usually from poor estimates
of exposure.”). Moreover, other studies have reached opposite results. See,
e.g., Spurgeon, et al., “Investigation of Dose Related Neurobehavioral Effects in
Paintmakers Exposed to Low Levels of Solvents,” Occupational & Environmental
7
Other s tudies ref erence d by the pa rties supp orting the th eory include Axleso n, et al.,
1976; Hanninen, et al., 1976; Hane, et al., 1977; Harkonen, et al., 1977; Knave, et al., 1978;
Mikkelson, 1980; and Gregersen, et al., 1987, among others.
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Medicine, 51:626-630 (1994)(cross sectional study of 110 paintmakers resulted
in view that “long term exposure at or below current compliance levels does not
result in damage to the central nervous system.”).
Despite the criticisms, textbooks and review articles recognize the
diagnosis of toxic encephalopathy. For example, in the chapter entitled “Organic
Solvents and Related Compounds” of the Textbook of Clinical Occupational and
Environmental Medicine, the authors state that “there is currently sufficient
support for the association of high long-term solvent exposure with long-lasting
psycho-organic symptoms to consider this a clinical reality.” Rosenstock and
Cullen, at p. 773 (1994).
International and national governmental health organizations also have
recognized the syndrome. For example, at the World Health Organization and
Nordic Council of Ministers meeting in Copenhagen, Denmark, in June 1985, it
was stated that “[c]linical, epidemiological and experimental data indicate that
long-term occupational exposure to organic solvents may cause adverse effects
in the central and the peripheral nervous systems.” It was recommended that
further “clinical, experimental and epidemiological studies should be undertaken
to gain further insight into the reversibility of the neurotoxic effects induced by the
solvents, their health significance and the dose-effect, dose-response
relationships.” Id. at pp. 32-33.
The National Institute for Occupational Safety and Health (“NIOSH”)
“Current Intelligence Bulletin 48,“ issued on March 31, 1989, makes similar
observations and recommends that producers and users inform their customers,
that trade associations and unions warn their workers, and that protective
equipment and worker education be used to reduce worker exposure -- at least
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to concentrations specified in exposure lists of OSHA and other organizations.
Id. at iii-iv.
Accordingly, as the trial court found, numerous epidemiological studies
support the diagnosis of toxic encephalopathy from exposure to solvents. W hile
other reports have criticized the epidemiological studies, the diagnosis is
recognized in textbooks and journals, as well as by national and world health
organizations. It is with this background that we now turn to the legal principles
governing the admissibility of scientific evidence.
SCIENTIFIC EVIDENCE
Nearly 75 years ago, the test for determining the admissibility of scientific
evidence was established in the landmark federal case of Frye v. United States,
293 F. 1013 (D.C. Cir. 1923). In Frye, which involved a polygraph examination,
or lie detector, the court said that scientific evidence will be admissible only if it
has “gained general acceptance in the particular field in which it belongs.” Id. at
1014. This rule, although followed by the vast majority of federal and state
jurisdictions, including Tennessee, was often criticized for being too restrictive of
relevant evidence, particularly new or “cutting edge” scientific theory, and too
vague for uniform application. See e.g., Symposium on Science and the Rules
of Evidence, 99 F.R.D. 188 (1983)(and extensive authority discussed therein).
The federal courts embarked on a new and less restrictive course with the
decision recently in Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579, 113
S.Ct. 2786, 125 L.Ed.2d 469 (1993), by the U. S. Supreme Court where the
Court reversed the 9th Circuit and determined that the “general acceptance” test
set forth in Frye was superseded by Fed. R. Evid. 702:
If scientific, technical, or other specialized knowledge will assist the
trier of fact to understand the evidence or to determine a fact in
issue, a witness qualified as an expert by knowledge, skill,
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experience, training, or education, may testify thereto in the form of
an opinion or otherwise.
According to the Court, Rule 702 requires a determination as to “whether the
expert is proposing to testify regarding scientific knowledge that will assist the
trier of fact to understand or determine a fact in issue.” Daubert, 509 U.S. at
592, 113 S.Ct. at 2796. This determination requires the trial court to consider
“whether the reasoning or methodology underlying the testimony is scientifically
valid and of whether the reasoning or methodology properly can be applied to
the facts in issue.” Id. In analyzing scientific validity or reliability, the trial court
must focus on “principles and methodology, and not on the conclusions they
generate.” Id., 509 U.S. at 595, 113 S.Ct. at 2797.
A partial list of factors the Supreme Court deemed relevant to the inquiry
included whether the theory or technique has been tested, whether it has been
subject to peer review or publication, whether there is a known or potential rate
of error, and whether, as formerly required under Frye, it is generally accepted in
the relevant scientific field. Id., 509 U.S. at 593-94, 113 S.Ct. at 2796-2798. On
remand, the Ninth Circuit Court of Appeals also considered whether the expert
proposes to testify about research conducted independent of litigation or whether
the expert had formulated an opinion for the express purpose of testifying.
Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311, 1317 (9th
Cir.)(“Daubert II”), cert. denied, 116 S.Ct. 189, 133 L.Ed.2d 126 (1995).
Daubert’s influence was felt in Joiner v. General Electric Co., 78 F.3d 524,
530 (11th Cir. 1996), cert. granted 117 S.Ct. 1243, 137 L.Ed.2d 325 (1997).
There, the trial court ruled that the plaintiff could not present expert testimony
that his exposure to polychlorinated biphenyls had caused lung cancer and
granted the defendant’s motion for summary judgment. On appeal, the Eleventh
Circuit, applying Daubert, emphasized:
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In analyzing the admissibility of expert testimony, it is important for
trial courts to keep in mind the separate functions of judge and jury,
and the intent of Daubert to loosen the strictures of Frye and make
it easier to present legitimate conflicting views of experts for the
jury’s consideration.
The court stressed the trial court’s role was a narrow one:
This gatekeeping role is simply to guard the jury from considering
as proof pure speculation presented in the guise of legitimate
scientifically-based expert opinion. It is not intended to turn judges
into jurors or surrogate scientists. Thus, the gatekeeping
responsibility of the trial courts is not to weigh or choose between
conflicting scientific opinions, or to analyze and study the science in
question in order to reach its own scientific conclusions from the
material in the field. Rather, it is to assure that expert’s opinions
are based on relevant scientific methods, processes, and data, and
not on mere speculation, and that they apply to the facts in issue.
Id. at 530 (emphasis added). After applying the Daubert inquiry and analyzing
the principles and methodology underlying the plaintiff’s scientific evidence, the
Eleventh Circuit Court of Appeals held that the trial court erred in excluding the
evidence.
Although the federal courts have decided a new and less restrictive
direction was appropriate, state courts are still wrestling with the choice between
Frye and Daubert. For example, in a case involving the exact same parties,
issues, and experts as the present case, a Florida state circuit court, applied the
Frye test, which was retained in that jurisdiction by the Florida Supreme Court,
and concluded that the epidemiological studies were inconsistent and that the
criticisms of these studies - that the plaintiffs had failed to show the evidence
was “generally accepted” in the relevant scientific community - were valid and,
therefore, ruled that the evidence was inadmissible. See Roy Lee Berry v. CSX
Transportation, Inc., No. 92-2167 (filed April 28, 1995).
On the other hand, in a federal case involving the exact same parties,
issues, and experts as the subject case, the federal district court for the
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Southern District of Georgia applied Daubert, and concluded that the evidence
was admissible. The district court found that the epidemiological studies
supported the plaintiff’s claim that exposure can cause impairment, and found
that the studies and results were scientifically valid and reliable notwithstanding
the criticisms by opposing experts and reports. The court rejected the
defendant’s claim that the plaintiffs must show causation with a relative risk or
odds ratio of 2.0 or greater. See Bob Allen, et al. v. CSX Transportation, Inc.,
(S.D. Ga., filed Sept. 10, 1996).
THE TENNESSEE STANDARD
After examining the basic legal principles governing the admissibility of
scientific evidence and the change in direction by the federal courts, we turn to
Tennessee to clarify our standard of admissibility.
In general, questions regarding the admissibility, qualifications, relevancy
and competency of expert testimony are left to the discretion of the trial court.
State v. Ballard, 855 S.W.2d 557, 562 (Tenn. 1993). The trial court’s ruling in
this regard may only be overturned if the discretion is arbitrarily exercised or
abused. Id. The specific rules of evidence that govern the issue of admissibility
of scientific proof in Tennessee are Tenn. R. Evid. 702 and 703.8 The former
provides:
If scientific, technical, or other specialized knowledge will
substantially assist the trier of fact to understand the evidence or to
determine a fact in issue, a witness qualified as an expert by
knowledge, skill, experience, training, or education may testify in
the form of an opinion or otherwise.
And Tenn. R. Evid. 703 states:
8
Of c ours e, sc ientific evide nce also m ust b e rele vant b efor e it is ad mis sible. As s tated in
Tenn. R. Evid. Rule 401, “[r]elevant evidence means evidence having any tendency to make the
existence of any fact that is of consequence to the determination of the action more probable or
less pro bable tha n it would be without the evidenc e.”
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The facts or data in the particular case upon which an expert bases
an opinion or inference may be those perceived by or made known
to the expert at or before the hearing. If of a type reasonably relied
upon by experts in the particular field in forming opinions or
inferences upon the subject, the facts or data need not be
admissible in evidence. The court shall disallow testimony in the
form of an opinion or inference if the underlying facts or data
indicate lack of trustworthiness.
The plaintiffs contend that the expert testimony in this case is reliable and
that it will substantially assist the jury on the issue of causation. The defendant
argues that irrespective of Frye or Daubert, there must be adherence to the strict
requirements contained in the language of the rules and also a reasonable
standard for proving causation. It contends that the plaintiffs’ scientific evidence
is unreliable and must be excluded. The defendant argues that an
epidemiological study must show a relative risk of greater than 2.0, which several
courts have said means that a disease more likely than not was caused by the
specific agent or event. See Daubert v. Merrell Dow Pharmaceuticals, Inc., 43
F.3d 1311 (9th Cir. 1995), cert. denied, 116 S.Ct. 189, 133 L.Ed.2d 126 (1995);
Deluca v. Merrell Dow Pharmaceuticals, Inc., 791 F.Supp. 1042 (D.N.J. 1992),
aff’d, 6 F.3d 778 (3rd Cir. 1993). As discussed herein, the factor is certainly
relevant but we reject the contention that it should be adopted as matter of law.
Although the advisory comments to Rule 702 indicate that Tennessee has
followed the Frye test in analyzing the admissibility of scientific evidence, one
commentator, recognizing the similarity between Tennessee Rule 702 and
Federal Rule Evid. 702, has raised the question of whether the Frye test of
“general acceptance” should be abolished in Tennessee. N. Cohen, S.
Sheppeard, and D. Paine, Tennessee Law of Evidence, § 401.20 at 124, n. 233.
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Indeed, as the trial court in this case noted, there is some evidence of a
departure from the strict adherence to the Frye test by courts in this State.9
In our view, determining the standard for the admissibility of scientific
evidence requires an analysis of the unique language found in Rules 702 and
703 of the Tennessee Rules of Evidence. For instance, Tenn. R. Evid. 702
requires that the scientific evidence “substantially assist the trier of fact,” while its
federal counterpart requires only that the evidence “assist the trier of fact.” Fed.
R. Evid. 702. This distinction indicates that the probative force of the testimony
must be stronger before it is admitted in Tennessee. See, e.g., Weinstein, Rule
702 of the Federal Rules of Evidence is Sound; It Should Not Be Amended, 138
F.R.D. 631, 636 (1991).
Similarly, Tenn. R. Evid. 703 states that “[t]he court shall disallow
testimony in the form of an opinion or inference if the underlying facts or data
indicate lack of trustworthiness.” There is no similar restriction in the federal rule.
Fed. R. Evid. 703. Thus, as one writer has observed, “the additional language
. . . [in the Tennessee rule] is obviously designed to encourage trial courts to
take a more active role in evaluating the reasonableness of the expert’s reliance
upon the particular basis for his or her testimony.” R. Banks, Some
Comparisons Between the New Tennessee Rules of Evidence and the Federal
Rules of Evidence, Part II, 20 Mem.S.U. L. Rev. 499, 559 (1990). In sum, even
though the facts and data need not be admissible, they must be reviewed and
found to be trustworthy by the trial court.
9
The trial judge identified four different standards used by Tennessee courts to determine
admissibility of scientific evidence: (1) “Scientifically acceptable and accurate for its purpose.”
State v. Johnson, 717 S.W.2d 298 (Tenn. Crim. App. 1986); (2) “Four-prong threshold test
involving whether the witness is an expert; whether the subject matter is proper; whether the
subject matter conforms to a generally-accepted theory; and whether the probative value of the
witness’ testimony outweighs its prejudicial effect.” State v. Schimpf, 782 S.W.2d 186 (Tenn.
Crim. App. 1989); (3) “ Frye or Tenn. R. Evid. 702 and 703 .” State v. Ha rris, 866 S.W.2d 583
(Tenn. Crim. App . 1992); and (4) “Analysis under several tests” State v. Myers, 1992 WL 297626
(Tenn. Crim. App . 1992).
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Based on the foregoing analysis, we conclude that Tennessee’s adoption
of Rules 702 and 703 in 1991 as part of the Rules of Evidence supersede the
general acceptance test of Frye. In Tennessee, under the recent rules, a trial
court must determine whether the evidence will substantially assist the trier of
fact to determine a fact in issue and whether the facts and data underlying the
evidence indicate a lack of trustworthiness. The rules together necessarily
require a determination as to the scientific validity or reliability of the evidence.
Simply put, unless the scientific evidence is valid, it will not substantially assist
the trier of fact, nor will its underlying facts and data appear to be trustworthy, but
there is no requirement in the rule that it be generally accepted.
Although we do not expressly adopt Daubert, the non-exclusive list of
factors to determine reliability are useful in applying our Rules 702 and 703. A
Tennessee trial court may consider in determining reliability: (1) whether
scientific evidence has been tested and the methodology with which it has been
tested; (2) whether the evidence has been subjected to peer review or
publication; (3) whether a potential rate of error is known; (4) whether, as
formerly required by Frye, the evidence is generally accepted in the scientific
community; and (5) whether the expert’s research in the field has been
conducted independent of litigation.
Although the trial court must analyze the science and not merely the
qualifications, demeanor or conclusions of experts, the court need not weigh or
choose between two legitimate but conflicting scientific views. The court instead
must assure itself that the opinions are based on relevant scientific methods,
processes, and data, and not upon an expert’s mere speculation. See, e.g.,
Joiner, 78 F.3d at 530. The trial court should keep in mind that the preliminary
question under Tenn. R. Evid. 104 is one of admissibility of the evidence. Once
the evidence is admitted, it will thereafter be tested with the crucible of vigorous
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cross-examination and countervailing proof. After that occurs, a defendant may,
of course, challenge the sufficiency of the evidence by moving for a directed
verdict at the appropriate times. See Tenn. R. Civ. P. 50. Yet it is important to
emphasize that the weight to be given to stated scientific theories, and the
resolution of legitimate but competing scientific views, are matters appropriately
entrusted to the trier of fact. See Joiner, 78 F.3d at 534-35 (Birch, J.,
concurring).
We recognize that the burden placed on trial courts to analyze and to
screen novel scientific evidence is a significant one. No framework exists that
provides for simple and practical application in every case; the complexity and
diversity of potential scientific evidence is simply too vast for the application of a
single test. See Developments in the Law -- Confronting the New Challenges of
Scientific Evidence, 108 Harv. L. Rev. 1481, 1513-1516 (1995). Nonetheless,
the preliminary questions must be addressed by the trial court, see, Tenn. R.
Evid. 104, and they must be addressed within the framework of rules 702 and
703.
APPLICATION OF STANDARD
The trial court correctly foresaw the trend away from Frye and also used
the factors set forth in Daubert as a framework for analysis. As it observed, the
scientific theory that exposure to solvents may cause toxic encephalopathy has
been tested frequently over a period of 25 years. Because no precise diagnostic
device or biological mechanism can isolate the causal factor, the relevant tests
have been epidemiological studies. The experts in this case testified at length
about the field of epidemiology and the use of cohort and case-control studies.
The experts agreed that epidemiological studies have been used to test the
hypothesis that exposure to solvents causes encephalopathy and that numerous
studies support a causal relationship. These studies have been reviewed,
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reconstructed, published in leading journals in the field, and subjected to peer
review. Although the “positive” studies have been criticized for failing to account
for confounding factors, the diagnosis is recognized in medical textbooks and
journals as well as by several national and world health organizations. We also
observe that the research in this area, including that of several of the plaintiffs’
experts, was conducted independently of this litigation.
Accordingly, we agree with the trial court’s finding that the evidence will
substantially assist the jury to understand the evidence and to determine a fact in
issue. We also agree with the trial court’s conclusion that the methodology and
principles underlying the scientific evidence are sufficiently trustworthy and
reliable to be presented to the trier of fact. The trial court is not required to
determine whether it agrees with the evidence and should not substitute its view
for the trier of fact. It should allow the jury to consider legitimate but conflicting
views about the scientific proof. Provided the evidence is scientifically valid,
criticisms of it and opposing views may be elicited on cross examination and/or
established in the defendant’s case. That is the essence of the lawsuit.
CONCLUSION
We have concluded that the scientific evidence proffered by the plaintiffs
satisfies the requirements of Tenn. R. Evid. 702 and 703, and that the trial court
did not abuse its discretion in admitting it into evidence. The trial court’s order
denying the defendant’s motion in limine is therefore affirmed and this case is
remanded to the trial court for further proceedings. Costs of the appeal are
assessed against the defendant.
________________________________
E. RILEY ANDERSON, CHIEF JUSTICE
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Concur:
Drowota, Reid, Birch and Holder, JJ.
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