Seisinger v. Siebel

SUPREME COURT OF ARIZONA
En Banc

LAURA SEISINGER, ) Arizona Supreme Court
) No. CV-08-0224-PR
Plaintiff/Appellant, )
) Court of Appeals
v. ) Division One
) No. 1 CA-CV 07-0266
SCOTT SIEBEL, M.D., )
) Maricopa County
Defendant/Appellee. ) Superior Court
) No. CV2004-015659
)
)
) O P I N I O N
__________________________________)

Appeal from the Superior Court in Maricopa County
The Honorable Michael D. Jones, Judge

VACATED AND REMANDED
________________________________________________________________

Opinion of the Court of Appeals, Division One
219 Ariz. 163, 195 P.3d 200 (App. 2008)

VACATED
________________________________________________________________

LAW OFFICES OF JAMES J. SYME, JR. Goodyear
By James J. Syme, Jr.
Attorneys for Laura Seisinger

JONES, SKELTON & HOCHULI, P.L.C. Phoenix
By J. Russell Skelton
Eileen Dennis GilBride
Attorneys for Scott Siebel

JENNINGS, STROUSS & SALMON, P.L.C. Phoenix
By John J. Egbert
Jay A. Fradkin
Attorneys for Amicus Curiae Mutual
Insurance Company of Arizona
SNELL & WILMER, L.L.P. Phoenix
By Barry D. Halpern
Scott A. Shuman
Rhonda Needham
Attorneys for Amici Curiae Arizona Medical Association, American
Medical Association, Arizona Hospital and Healthcare
Association, Maricopa County Medical Society, Pima County
Medical Society, Arizona Osteopathic Medical Association,
American Association of Orthopaedic Surgeons, Arizona Chapter of
the American Academy of Orthopaedic Surgeons, The American
College of Obstetricians and Gynecologists, American College of
Cardiology, Arizona Chapter of the American College of
Cardiology, Arizona Society of Anesthesiologists, and Arizona
Radiological Society

LAW OFFICE OF JOJENE MILLS, P.C. Tucson
By JoJene E. Mills
Attorneys for Amicus Curiae Arizona Trial Lawyers Association
________________________________________________________________

H U R W I T Z, Justice

¶1 The issue before us is whether A.R.S. § 12-2604(A)

(Supp. 2008), which governs proof of the standard of care in

medical malpractice cases, violates the separation of powers

doctrine.

I.

¶2 Scott Siebel, M.D., an anesthesiologist, administered

a spinal epidural to Laura Seisinger in 2002. Two years later,

Seisinger filed a complaint against Seibel alleging malpractice.

Seisinger subsequently disclosed that J. Antonio Aldrete, M.D.,

would testify as an expert about the appropriate standard of

care.

¶3 When the defendant in a medical malpractice action is

a specialist, § 12-2604(A) requires an expert witness on the
2
standard of care to have devoted a majority of his professional

time in the year preceding the incident at issue to active

clinical practice or teaching in the same specialty.1 Dr. Siebel

_______________________________ 
1
Section 12-2604(A) provides:

A. In an action alleging medical malpractice, a person
shall not give expert testimony on the appropriate
standard of practice or care unless the person is
licensed as a health professional in this state or
another state and the person meets the following
criteria:

1. If the party against whom or on whose behalf
the testimony is offered is or claims to be a
specialist, specializes at the time of the
occurrence that is the basis for the action in
the same specialty or claimed specialty as the
party against whom or on whose behalf the
testimony is offered. If the party against whom
or on whose behalf the testimony is offered is or
claims to be a specialist who is board certified,
the expert witness shall be a specialist who is
board certified in that specialty or claimed
specialty.

2. During the year immediately preceding the
occurrence giving rise to the lawsuit, devoted a
majority of the person’s professional time to
either or both of the following:

(a) The active clinical practice of the same
health profession as the defendant and, if
the defendant is or claims to be a
specialist, in the same specialty or claimed
specialty.

(b) The instruction of students in an
accredited health professional school or
accredited residency or clinical research
program in the same health profession as the
defendant and, if the defendant is or claims
to be a specialist, in an accredited health

3
filed a motion contending that Dr. Aldrete, a retired

anesthesiologist, did not meet the temporal practice or teaching

requirement in § 12-2604(A)(2). Seisinger did not dispute the

motion’s factual assertions, but argued that § 12-2604(A)

conflicts with Arizona Rule of Evidence 702 and violates the

separation of powers doctrine set forth in Article 3 of the

Arizona Constitution. Rule 702 provides that “a witness

qualified as an expert by knowledge, skill, experience,

training, or education” may provide testimony that “will assist

the trier of fact to understand the evidence or to determine a

fact in issue.”

¶4 The superior court rejected Seisinger’s constitutional

argument and granted the motion in limine. The court gave

Seisinger additional time to disclose a new expert qualified

_________________________________ 
professional school or accredited residency
or clinical research program in the same
specialty or claimed specialty.

3. If the defendant is a general practitioner,
the witness has devoted a majority of the
witness’s professional time in the year preceding
the occurrence giving rise to the lawsuit to
either or both of the following:

(a) Active clinical practice as a general
practitioner.

(b) Instruction of students in an accredited
health professional school or accredited
residency or clinical research program in
the same health profession as the defendant.

4
under § 12-2604(A). After she failed to do so, the court

granted Dr. Siebel’s motion to dismiss.

¶5 The court of appeals reversed. Seisinger v. Siebel,

219 Ariz. 163, 164-65 ¶ 1, 195 P.3d 200, 201-02 (App. 2008). It

held that § 12-2604(A) conflicts with Rule 702 because the

statute categorically excludes potential experts qualified to

testify under the Rule. Id. at 166-67 ¶¶ 9-13, 195 P.3d at 203-

04. The court of appeals also held that § 12-2604(A) did not

establish substantive rights. Id. at 169-70 ¶¶ 20-21, 195 P.3d

206-07. The court therefore found that the statute violated the

separation of powers doctrine by infringing upon this Court’s

authority under Article 6, Section 5(5) of the Arizona

Constitution to promulgate procedural rules. Id. at 170 ¶ 22,

195 P.3d at 207.

¶6 We granted review because the case involves the

constitutionality of a statute and the issues presented are of

statewide importance. See ARCAP 23(c). We have jurisdiction

under Article 6, Section 5(3) of the Arizona Constitution and

A.R.S. § 12-120.24 (2003).

II.

A.

¶7 The Arizona Constitution commands that the

legislative, executive, and judicial departments “shall be

separate and distinct, and no one of such departments shall
5
exercise the powers properly belonging to either of the others.”

Ariz. Const. art. 3. The Constitution also vests this Court

with “[p]ower to make rules relative to all procedural matters

in any court.” Id. art. 6, § 5(5). Rules of evidence “have

generally been regarded as procedural in nature.” State ex rel.

Collins v. Seidel, 142 Ariz. 587, 590, 691 P.2d 678, 681 (1984).

¶8 Although we have occasionally said that procedural

rulemaking power is vested “exclusively” in this Court, State v.

Hansen, 215 Ariz. 287, 289 ¶ 9, 160 P.3d 166, 168 (2007); Daou

v. Harris, 139 Ariz. 353, 357-58, 678 P.2d 934, 938-39 (1984),

this statement is in some respects an oversimplification. A

statutory procedural enactment is not automatically invalid.

See Seidel, 142 Ariz. at 591, 691 P.2d at 682 (“That we possess

the rule-making power does not imply that we will never

recognize a statutory rule.”). Rather, we recognize “reasonable

and workable” statutory enactments that supplement rather than

conflict with rules we have promulgated. Id. (citation and

internal quotation marks omitted); see Readenour v. Marion Power

Shovel, 149 Ariz. 442, 445, 719 P.2d 1058, 1061 (1986) (defining

determinative issue as whether the statute “supplement[s] rather

than contradict[s]” an evidentiary rule). Therefore, it is more

accurate to say that the legislature and this Court both have

rulemaking power, but that in the event of irreconcilable

6
conflict between a procedural statute and a rule, the rule

prevails.

¶9 The legislature thus cannot repeal a rule of procedure

or evidence. Seidel, 142 Ariz. at 591, 691 P.2d at 682. But a

statute may “contradict” or effectively abrogate a rule even if

there is no express repeal. Accordingly, the legislature cannot

enact a statute that “provides an analytical framework contrary

to the rules” of evidence. Barsema v. Susong, 156 Ariz. 309,

314, 751 P.2d 969, 974 (1988).

¶10 Determining whether a statute unduly infringes on our

rulemaking power requires analysis of the particular rule and

statute said to be in conflict. Our cases provide some guidance

on purported conflicts between statutes and rules of evidence.

In Readenour, this Court upheld against a separation of powers

attack A.R.S. § 12-686(2), which makes inadmissible “as direct

evidence of a defect” evidence of changes made by the

manufacturer after “the product was first sold by the

defendant.” 149 Ariz. at 444 n.1, 719 P.2d at 1060 n.1. The

allegedly conflicting evidence rule was Rule 407, which makes

remedial measures taken after an event supposedly giving rise to

liability inadmissible “to prove negligence or culpable

conduct.” Rule 407 excludes from its general prohibition

evidence offered for other purposes, such as to prove

“ownership, control, or feasibility of precautionary measures.”
7
Readenour argued that the statute, by making inadmissible post-

sale changes, conflicted with the Rule, which excludes only

post-incident changes. Readenour, 149 Ariz. at 445, 719 P.2d at

1061.

¶11 We began from the proposition that “it is our duty to

save a statute, if possible, by construing it so that it does

not violate the constitution.” Id. (citing Ariz. Downs v. Ariz.

Horsemen’s Found., 130 Ariz. 550, 554, 637 P.2d 1053, 1057

(1981)). We therefore interpreted § 12-686(2), which prohibits

evidence of changes only “as direct evidence of a defect,” as

permitting the uses of such evidence allowed under Rule 407.

Id. This interpretation avoided any conflict between the

statute and the exceptions in the Rule.

¶12 We then concluded that the statute’s application to

pre-injury but post-sale changes did not conflict with the Rule.

Id. The Rule is silent on the admissibility of post-sale, pre-

injury changes, so the statute did not expressly abrogate the

Rule. Nor did the statute undermine the purposes of Rule 407.

We concluded that the policy of the Rule is to encourage

remedial measures, the probative value of the evidence excluded

is not high, and the extension of the prohibition to this period

fosters the policy embodied in the Rule. Id. at 445-46, 719

P.2d at 1061-62. We therefore “defer[red] to the legislative

decisions regarding the use or exclusion of relevant evidence to
8
promote substantive goals of public policy such as accident

prevention.” Id. at 446, 719 P.2d at 1062. We also noted that

§ 12-686(2) “is similar to a privilege statute, having both

procedural and substantive aspects.” Id.

¶13 In contrast, in Barsema we found that a statute

unconstitutionally conflicted with a rule of evidence. There,

the statute at issue, A.R.S. § 12-569, prohibited “for any

purpose” the admission of evidence that a witness has been or is

covered by a certain type of medical malpractice insurer or has

a financial interest in the operation of such an insurer.

Barsema, 156 Ariz. at 311-12, 751 P.2d at 971-72. The

conflicting rule was Evidence Rule 411, which prohibits

admission of evidence that “a person was or was not insured

against liability . . . upon the issue whether the person acted

negligently or otherwise wrongfully,” but allows admission of

such evidence when offered for another purpose, such as proof of

“bias or prejudice of a witness.”

¶14 Under Rule 411, evidence that a witness was insured

could be admitted for purposes other than establishing liability

if the trial judge found that it met the general Rule 402

requirement of relevancy and the Rule 403 requirement that its

probative value was not “substantially outweighed by the danger

of unfair prejudice” or other factors. Barsema, 156 Ariz. at

313, 751 P.2d at 973. In contrast, § 12-569 prohibited the use
9
of such evidence “for any purpose.” We were thus unable, as in

Readenour, to construe the statute to avoid conflict with the

rule. Instead, the mandate of Rule 411 – that evidence of

insurance offered for purposes other than to establish liability

is to be evaluated on a case-by-case basis under Rules 402 and

403 – had been superseded by a statutory regime in which the

evidence was always excluded. We therefore concluded that § 12-

569 unduly infringed on our rulemaking power because it does not

“merely supplement[]” Rule 411, but rather “provides an

analytical framework contrary to the rules.” Id. at 314, 751

P.2d at 974.

B.

¶15 In this case, the court of appeals held that § 12-

2604(A) conflicted with Rule 702 “because the statute cannot be

harmonized with the Rule.” Seisinger, 219 Ariz. at 169 ¶ 19,

195 P.3d at 206. We agree.

¶16 Rule 702 permits expert testimony to “assist the trier

of fact to understand the evidence or to determine a fact in

issue” when a witness is “qualified as an expert by knowledge,

skill, experience, training, or education.” “The test of

whether a person is an expert is whether a jury can receive help

on a particular subject from the witness. The degree of

qualification goes to the weight given the testimony, not its

10
admissibility.” State v. Davolt, 207 Ariz. 191, 210 ¶ 70, 84

P.3d 456, 475 (2004) (citation omitted).

¶17 Dr. Siebel argues that there is no conflict between

the statute and the Rule because § 12-2604(A) simply assures

that an expert witness has the qualifications required by the

Rule. But the statute makes clear that its requirements are in

addition to those in Rule 702. Section 12-2604(C) provides that

“[t]his section does not limit the power of the trial court to

disqualify an expert witness on grounds other than the

qualifications set forth in this section.” The expert therefore

must both possess the qualifications required by Rule 702 and

satisfy the additional requirements of § 12-2604(A).

¶18 Thus, as the court of appeals noted, § 12-2604(A)

“precludes a witness who is otherwise qualified under Rule 702

from testifying in a medical malpractice case unless he or she

meets the additional criteria set forth in the statute.”

Seisinger, 219 Ariz. at 167 ¶ 13, 195 P.3d at 204. To be sure,

a trial judge could conclude under Rule 702 that a particular

physician who has not recently practiced or taught is not

qualified to testify about the current standard of care. But,

particularly when the standard of care has not materially

changed during the period after a physician left active practice

or teaching, a trial judge might also well conclude that the

witness remains qualified through “knowledge, skill, experience,
11
training, or education” to assist the jury through expert

testimony. As to such a witness, the statute automatically

produces a different result than the Rule might produce.

Indeed, such was the obvious intent of the statute: It is

designed to limit which physicians are qualified to express

expert opinions. See Minutes of Meeting: Hearing on S.B. 1036

Before the H. Comm. on Health, 47th Leg., 1st Reg. Sess. (Ariz.

Mar. 23, 2005) (statement of Sen. Robert Cannell, co-sponsor of

measure containing § 12-2604(A), that “physicians do not want

retired physicians to testify against them”).

¶19 Consequently, we agree with the court of appeals that

§ 12-2604(A) and Rule 702 are in “direct conflict.” Seisinger,

219 Ariz. at 167 ¶ 13, 195 P.3d at 204. In interpreting a

similar statute, the Michigan Supreme Court reached precisely

this conclusion, noting that the legislature “envisioned and

intended that the statute would often compel different

qualification determinations than the rule when applied to a

given case.” McDougall v. Schanz, 597 N.W.2d 148, 153 (Mich.

1999).

¶20 Several federal cases have held that state statutes

similar to § 12-2604(A) must be applied in diversity cases

notwithstanding Federal Rule of Evidence 702. See, e.g., Legg

v. Chopra, 286 F.3d 286, 291-92 (6th Cir. 2002); see also

McDowell v. Brown, 392 F.3d 1283, 1294-95 (11th Cir. 2004)
12
(following Legg); Miville v. Abington Mem’l Hosp., 377 F. Supp.

2d 488, 493 (E.D. Pa. 2005) (same). These cases, however, are

not contrary to our conclusion that § 12-2604(A) conflicts with

Arizona Rule of Evidence 702.

¶21 The federal cases interpret Federal Rule of Evidence

601, which provides that “in civil actions and proceedings, with

respect to an element of a claim or defense as to which State

law supplies the rule of decision, the competency of a witness

shall be determined in accordance with State law.” Therefore,

the conclusion by the federal courts that the state statutes

enacted a rule of competency compelled application of the state

law. Moreover, the question of whether a federal court sitting

in diversity applies state or federal law turns under Erie

Railroad Co. v. Tompkins, 304 U.S. 64 (1938), on notions of

federalism, not separation of powers. Congress has no more

ability through legislation than does the Supreme Court of the

United States through rulemaking to prescribe the substantive

rules of decision in diversity cases. See Hanna v. Plumer, 380

U.S. 460, 471-72 (1965) (“[N]either Congress nor the federal

courts can . . . fashion rules which are not supported by a

grant of federal authority contained in Article I or some other

section of the Constitution; in such areas state law must govern

because there can be no other law.”).

13
¶22 In contrast to the federal rule, Arizona Rule of

Evidence 601 states: “Every person is competent to be a witness

except as otherwise provided in these rules or by statute.” The

Arizona Rule is silent as to the effect of a conflict between a

rule and a statute. Thus, even assuming that § 12-2604(A) is a

rule of competency, see Kenneth S. Broun et al., McCormick on

Evidence § 69, at 332 (6th ed. 2006) (characterizing the

qualification requirements in Federal Rule of Evidence 702 as

competency requirements), the question nonetheless remains under

Article 3 and Article 6, Section 5(5), whether the statute

impermissibly conflicts with Rule 702.

¶23 Our prior cases illustrate the point. For example,

Rule 402 provides that “[a]ll relevant evidence is admissible,

except as otherwise provided by the Constitution of the United

States, by the Constitution of Arizona or by applicable statutes

or rules.” But in Readenour, we stated that we “cannot let the

legislature define what is relevant.” 149 Ariz. at 446, 719

P.2d at 1062. And in Barsema, we struck down a statute that

effectively modified the relevancy rules notwithstanding the

“except as otherwise provided” language of Rule 402. Barsema,

156 Ariz. at 314, 751 P.2d at 974. Similarly, Rule 802 provides

that hearsay is inadmissible “except as provided by applicable

constitutional provisions, statutes, or rules.” Nonetheless, in

State v. Robinson, we struck down a legislative exception to the
14
hearsay rules under the separation of powers doctrine. 153

Ariz. 191, 197-98, 735 P.2d 801, 807-08 (1987).

III.

A.

¶24 As the court of appeals recognized, a determination

that a statute and court rule cannot be harmonized is but the

first step in a separation of powers analysis. Seisinger, 219

Ariz. at 169 ¶ 20, 195 P.3d at 206. If there is a conflict, as

the court of appeals recognized, id., we must then determine

whether the challenged statutory provision is substantive or

procedural. See, e.g., Valerie M. v. Ariz. Dep’t of Econ. Sec.,

219 Ariz. 331, 336 ¶ 21, 198 P.3d 1203, 1208 (2009); Hansen, 215

Ariz. at 289 ¶ 9, 160 P.3d at 168 (“[W]hen a statute and a rule

conflict, we traditionally inquire into whether the matter

regulated can be characterized as substantive or procedural, the

former being the legislature’s prerogative and the latter the

province of this Court.”); State v. Fowler, 156 Ariz. 408, 410-

11, 752 P.2d 497, 499-500 (App. 1987).

¶25 The court of appeals concluded that § 12-2604(A) is

not substantive because “the legislative history of the

enactment of § 12-2604(A) does not establish that the Arizona

Legislature had concerns regarding the right to sue, limiting

the right to sue or changing the burden of proof to prevail in

medical malpractice cases.” Seisinger, 219 Ariz. at 170 ¶ 21,
15
195 P.3d at 207. Even assuming the factual accuracy of this

statement,2 however, the issue of whether an enactment is

procedural or substantive cannot turn on the record made in

legislative hearings. The question is instead one of law.

¶26 This legal inquiry, like the determination of whether

a rule and a statute conflict, is mandated by fundamental

concepts of separation of powers. Article 4, Part 1, Section 1

of the Arizona Constitution vests the legislature (and the

people through ballot measure) with the “legislative authority”

of the State. The legislature has plenary power to deal with

any topic unless otherwise restrained by the Constitution. Giss

v. Jordan, 82 Ariz. 152, 159, 309 P.2d 779, 783-84 (1957); Adams

v. Bolin, 74 Ariz. 269, 283, 247 P.2d 617, 626 (1952). Thus,

once we determine that a statute conflicting with a court-

promulgated rule is “substantive,” the statute must prevail.

See Valerie M., 219 Ariz. at 336 ¶ 21, 198 P.3d at 1208; Hansen,

215 Ariz. at 289 ¶ 10, 160 P.3d at 168 (“[I]if [the conflicting

statute] is substantive, it indisputably governs.”).

_______________________________ 
2
The accuracy of this statement is at least subject to
question. A co-sponsor of the bill that contained § 12-2604(A)
stated that his goal was “to improve the malpractice climate in
our state,” encourage physicians to practice here, and lower
medical malpractice rates. Minutes of Meeting: Hearing on S.B.
1036 Before the H. Comm. on Health, 47th Leg., 1st Reg. Sess.
(Ariz. Mar. 23, 2005) (statement of Sen. Robert Cannell).

16
¶27 Just as the primacy of the courts in promulgating

procedural rules does not exclude a supplementary legislative

role, our Constitution does not prohibit the judiciary from

developing substantive law. An obvious example of this role is

in the area of the common law. The legislature has expressly

provided that the “common law . . . is adopted and shall be the

rule of decision in all courts of this state.” A.R.S. § 1-201

(2002).3 The American legal tradition relies on courts to make

substantive law through the development of the common law. See

Cronin v. Sheldon, 195 Ariz. 531, 537, 991 P.2d 231, 237 (1999)

(“Courts do make law. The common law is and has been a product

of the courts for hundreds of years. To adopt the common law

is, by definition, to adopt the plenary role of the judiciary in

its continuing development.”).

¶28 But just as a procedural statute cannot prevail

against a procedural rule validly promulgated under Article 6,

judge-made substantive law is subordinated to contrary

legislative acts validly adopted under Article 4. Section 1-201

recognizes this basic constitutional principle, adopting the

common law only insofar as it is “not repugnant to or

inconsistent with the constitution of the United States or the

_______________________________ 
3
The sentiment expressed in § 1-201 was first adopted in
1907 Ariz. Sess. Laws ch. 10, § 8, and has been part of every
succeeding Arizona code.

17
constitution or the laws of this state.” Thus, when a

substantive statute conflicts with the common law, the statute

prevails under a separation of powers analysis. See Pleak v.

Entrada Prop. Owners’ Ass’n, 207 Ariz. 418, 422 ¶ 12, 87 P.3d

831, 835 (2004).

1.

¶29 Although the basic constitutional principle of

separation of powers is easily stated, the precise dividing line

between substance and procedure “has proven elusive.” In re

Shane B., 198 Ariz. 85, 88 ¶ 9, 7 P.3d 94, 97 (2000). In an

oft-quoted passage, this Court stated that

the substantive law is that part of the law which
creates, defines and regulates rights; whereas the
adjective, remedial or procedural law is that which
prescribes the method of enforcing the right or
obtaining redress for its invasion. It is often said
the adjective law pertains to and prescribes the
practice, method, procedure or legal machinery by
which the substantive law is enforced or made
effective.

State v. Birmingham, 96 Ariz. 109, 110, 392 P.2d 775, 776

(1964). This definition, while unexceptionable, unfortunately

does not provide an answer in close cases. Statutes relating to

evidence present particularly difficult problems, as such

statutes, like rules of evidence, often have both substantive

and procedural aspects. See Readenour, 149 Ariz. at 446, 719

P.2d at 1062 (noting that § 12-682(2) has “both procedural and

substantive aspects”); cf. Legg, 286 F.3d at 290 (“[S]ome state
18
evidentiary rules have substantive aspects, thereby defying the

substance-procedure distinction.”).4 The relevant inquiry

therefore cannot end, as our concurring colleague suggests, see

¶ 52, infra, with the conclusion that there is some conflict

between a validly enacted rule of evidence and a statute.5 The

ultimate question is whether the statute enacts, at least in

relevant part, law that effectively “creates, defines, and

_______________________________ 
4
The federal courts have also struggled to define the
distinction between substance and procedure in developing the
Erie doctrine. In arguably the most articulate attempt to
resolve this problem, Justice Harlan once wrote that “the proper
line of approach in determining whether to apply a state or a
federal rule, whether ‘substantive’ or ‘procedural,’ is to stay
close to basic principles by inquiring if the choice of rule
would substantially affect those primary decisions respecting
human conduct which our constitutional system leaves to state
regulation.” Hanna, 380 U.S. at 475 (Harlan, J., concurring)
(citing Henry M. Hart, Jr. & Herbert Wechsler, The Federal
Courts and the Federal System 678 (1953)). The federal cases
interpreting Erie, however, provide only limited guidance
because they address issues of federalism, not separation of
powers between coordinate branches of government. See ¶¶ 20-21,
supra.
5
Arizona Rule of Evidence 407, for example, codifies the
common law rule generally making certain remedial measures
inadmissible as proof of prior negligence. The Rule plainly
reflects a substantive policy decision — that it is more
important to encourage remedy of defects than to allow
plaintiffs to use arguably relevant evidence as proof of
negligence. Although we need not today address the issue
conclusively, it would seem that the legislature would be free
to enact a contrary policy decision, allowing use of such
evidence when its probative value is not substantially
outweighed by potential prejudice. Cf. Readenour, 149 Ariz. at
446, 719 P.2d at 1062 (concluding that statute expanding
exclusion of remedial measures beyond that required by Rule 407
had “both procedural and substantive aspects”).

19
regulates rights.”

¶30 Even if a litmus test as to what is substantive is not

possible, our cases do provide guidance. “Because the

legislature is empowered to set burdens of proof as a matter of

substantive law, a valid statute specifying the burden of proof

prevails over common law or court rules adopting a different

standard.” Valerie M., 219 Ariz. at 336 ¶ 21, 198 P.3d at 1208;

see State v. Fletcher, 149 Ariz. 187, 191-93, 717 P.2d 866, 870-

72 (1986) (holding that burden of proof of insanity is

substantive and may be altered by the legislature). We have

also recognized that common law privileges are substantive and

generally subject to legislative amendment. See Readenour, 149

Ariz. at 446, 719 P.2d at 1062; State v. Whitaker, 112 Ariz.

537, 540, 544 P.2d 219, 222 (1975). Similarly, the legislature

may modify the elements of common law causes of action, subject

to constitutional constraints not at issue in this case. See

Duncan v. Scottsdale Med. Imaging, Ltd., 205 Ariz. 306, 314 n.2,

70 P.3d 435, 443 n.2 (2003) (recognizing that legislature may

regulate tort elements, subject to constraints imposed by

Arizona Constitution article 18, § 6); cf. McDougall, 597 N.W.2d

at 158-59 (noting legislative ability to modify elements of

causes of action).

¶31 Because § 12-2604(A) provides that certain expert

testimony cannot be received, Seisinger argues that it must be
20
procedural. But, as Readenour teaches, a statute excluding

evidence is not inevitably procedural; privilege statutes

exclude highly relevant evidence but are nonetheless

substantive. 149 Ariz. at 446, 719 P.2d at 1062. We thus

approach our analysis of § 12-2604(A) with the goal of

determining, absent labels, the true function of the statute.6

We do so mindful of our duty to construe legislation, if

possible, so that it does not violate the constitution.

Readenour, 149 Ariz. at 446, 719 P.2d at 1062.

2.

¶32 In medical malpractice actions, as in all negligence

actions, the plaintiff must prove the existence of a duty, a

_______________________________ 
6
For the same reason, we are skeptical that the issue can be
resolved, as the concurrence suggests, simply by characterizing
§ 12-2604(A) as usurping a “core judicial function[].” See
¶ 64, infra. The dividing line between “core” functions and
others is no more apparent in difficult cases than that between
procedural and substantive enactments. Perhaps more
importantly, we have previously stated that Rule 702 does not
involve a “core” judicial function. We noted in Robinson that,
“[u]nlike the rules affected by statutes at issue in Seidel or
Readenour, the hearsay rules are at the core of the judicial
function.” 153 Ariz. at 197, 735 P.2d at 801. Seidel involved
Rule 702. See 142 Ariz. at 590, 691 P.2d at 681.

Moreover, although the cases involving Federal Rule of
Evidence 702 and statutes similar to § 12-2604(A) are
distinguishable, see ¶¶ 20-22, supra, they surely suggest at
least that a state legislature does not assume a “core” judicial
role in enacting such statutes. Were such the case, Article III
courts would seem constrained by separation of powers principles
implicit in the federal constitution to find these statutes
unenforceable.

21
breach of that duty, causation, and damages. Smethers v.

Campion, 210 Ariz. 167, 170 ¶ 12, 108 P.3d 946, 949 (App. 2005).

The “yardstick by which a physician’s compliance with [his] duty

is measured is commonly referred to as the ‘standard of care.’”

Id. ¶ 13.

¶33 Under the common law, breach of duty in malpractice

actions required proof that the defendant failed to exercise the

“same care in the performing of his duties as was ordinarily

possessed and exercised by other physicians of the same class in

the community in which he practiced.” Rice v. Tissaw, 57 Ariz.

230, 237-38, 112 P.2d 866, 869 (1941) (citing Butler v. Rule, 29

Ariz. 405, 242 P. 436 (1926)). Arizona courts have long held

that the standard of care normally must be established by expert

medical testimony. See, e.g., Riedisser v. Nelson, 111 Ariz.

542, 544, 534 P.2d 1052, 1054 (1975); Stallcup v. Coscarart, 79

Ariz. 42, 46, 282 P.2d 791, 793-94 (1955); Boyce v. Brown, 51

Ariz. 416, 421, 77 P.2d 455, 457 (1938).7 Thus, except when it

_______________________________ 
7
The Arizona cases mirror the general common law rule. See,
e.g., Ewing v. Goode, 78 F. 442, 444 (C.C.S.D. Ohio 1897)
(“[W]hen a case concerns the highly specialized art of treating
an eye for cataract, or for the mysterious and dread disease of
glaucoma, with respect to which a layman can have no knowledge
at all, the court and jury must be dependent on expert evidence.
There can be no other guide, and, where want of skill or
attention is not thus shown by expert evidence applied to the
facts, there is no evidence of it proper to be submitted to the
jury.”); McGraw v. Kerr, 128 P. 870, 874 (Colo. 1912) (“The
authorities are practically uniform in holding[,] and counsel

22
was “a matter of common knowledge . . . that the injury would

not ordinarily have occurred if due care had been exercised,”

Falcher v. Saint Luke’s Hosp. Med. Ctr., 19 Ariz. App. 247, 250,

506 P.2d 287, 290 (1973), a plaintiff could not meet the burden

of production under the common law absent expert testimony.8

Failure to produce the required expert testimony mandated

judgment for the physician-defendant. See, e.g., Rodriguez v.

Jackson, 118 Ariz. 13, 17, 574 P.2d 481, 485 (App. 1978).

¶34 Arizona courts have also long held that expert

testimony on the standard of care can be presented only by a

physician. Rice, 57 Ariz. at 238, 112 P.2d at 869. Therefore,

a plaintiff producing only the testimony of a nurse or a

pharmacologist on the standard of care has not satisfied the

substantive burden of proof, and his claim is subject to summary

disposition. See Rudy v. Meshorer, 146 Ariz. 467, 470, 706 P.2d

1234, 1237 (App. 1985) (“The testimony of a registered nurse

cannot be used to establish the standard of care a doctor must

meet.”); Rodriguez, 118 Ariz. at 17, 574 P.2d at 485.
_________________________________ 
for the plaintiff admits, that as to what is or is not proper
practice in examination and treatment, or the usual practice and
treatment, is a question for experts, and can be established
only by their testimony.”).
8
Section 12-2604(A) does not purport to abolish the common-
law res ipsa loquitur doctrine. Rather, the statute applies
only to those cases in which expert testimony is otherwise
required. Sanchez v. Old Pueblo Anesthesia, P.C., 218 Ariz.
317, 321 ¶ 14, 183 P.2d 1285, 1289 (App. 2008).

23
¶35 Arizona common law decisions requiring expert

testimony from physicians in medical malpractice cases long

predated the adoption of the Arizona Rules of Evidence in 1977.

Thus, as a purely chronological matter, the requirement of a

physician expert cannot be said to have resulted from our

promulgation of a procedural rule. More importantly, the common

law doctrine is far stricter than Rule 702. Our decisions hold

that a plaintiff cannot satisfy the burden of production absent

an expert physician witness; failure to produce such a witness

results in judgment for the defendant. In contrast, Rule 702

does not require that a plaintiff produce expert testimony in

any case. Rather, the Rule simply permits expert testimony when

the finder of fact would thereby be aided. Nor does Rule 702

purport to require that experts on the standard of care be

physicians. Rather, the Rule leaves to the trial judge the

determination of whether the witness possesses the required

“knowledge, skill, experience, training or education.”

¶36 Accordingly, even when the Dean of the College of

Nursing at the University of Arizona testified that a registered

nurse could, under many circumstances, be qualified both by

training and experience to know the applicable standard of care,

the court of appeals concluded that summary judgment for the

defendant was required when there was no testimony from a

medical doctor. Rodriguez, 118 Ariz. at 16-17, 574 P.2d at 484-
24
85; see also id. (reaching same conclusion as to Ph.D.

pharmacologist despite similar testimony from associate dean of

medical school); Rudy, 146 Ariz. at 470, 706 P.2d at 1237

(affirming summary judgment when the only testimony on standard

of care came from registered nurse).

¶37 In short, the requirement of expert physician

testimony in a medical malpractice action is not simply the

result of Rule 702 or some other procedural rule. Our decisions

requiring expert physician testimony do not turn on a case-by-

case examination of the training or qualifications of any

individual expert. Rather, they teach that a plaintiff cannot

satisfy the burden of proving a required element of the tort in

the absence of a very specific kind of evidence. To establish

the requisite standard of care, Arizona cases do not accept just

any kind of expert witness, but rather demand a physician.

¶38 We therefore conclude that the requirement of expert

testimony in a medical malpractice action is a substantive

component of the common law governing this tort action. The

common law requirement reflected a policy decision by the courts

that the plaintiff’s substantive burden of production could only

be met by a particular kind of evidence. The common law

requirement thus effectively established an element of the cause

of action, by specifying the kind of proof necessary to meet the

plaintiff’s burden of production.
25
¶39 The common law elements of a medical malpractice

action have now been partially codified by the legislature in

A.R.S. § 12-563. Because § 12-563 defines the elements of a

cause of action, it is plainly substantive. Section 12-2604(A)

is substantive in much the same sense. It “regulates rights,”

Birmingham, 96 Ariz. at 110, 392 P.2d at 776, by modifying the

common law to increase a plaintiff’s burden of production with

respect to a statutory element of the tort, departure from the

standard of care. Before the enactment of § 12-2604(A),

Seisinger could satisfy that burden by presenting the testimony

of Dr. Aldrete, assuming he qualifies as an expert under Rule

702. After § 12-2604(A) became effective, the same evidence is

not sufficient, as a matter of law, to avoid summary judgment.

The statute thus did not merely alter court procedures, but

rather changed the substantive law as to what a plaintiff must

prove in medical malpractice actions. Cf. Peck v. Tegtmeyer,

834 F. Supp. 903, 909 (W.D. Va. 1992) (“In other words, under

the statutory scheme, the standard of care is that which is

testified to by an expert qualified under the statute.”), aff’d

mem., 4 F.3d 985 (4th Cir. 1993); Legg, 286 F.3d at 290 (“State

witness competency rules are often intimately intertwined with a

state substantive rule. This is especially true with medical

malpractice statutes, because expert testimony is usually

required to establish the standard of care.”).
26
¶40 Our conclusion that § 12-2604(A) is substantive

insofar as it requires a certain type of evidence to prove an

element of the tort does not, as our concurring colleague

suggests, “shift[] the established boundaries of judicial and

legislative domains.” See ¶ 60, infra. The doctrine of

separation of powers does not constrain the legislature from

modifying, or even abolishing, the elements of common law causes

of action. See ¶ 30, supra. Nor do separation-of-powers

principles restrict the legislature’s ability to increase the

plaintiff’s common law burden of proof. See id. If separation

of powers would not prevent the legislature from requiring that

all medical malpractice plaintiffs prove claims beyond a

reasonable doubt, it is difficult to see why the legislature

cannot require a heightened level of proof of the standard of

care.

¶41 Although we maintain plenary power over procedural

rules, we do not believe that power precludes the legislature

from addressing what it believes to be a serious substantive

problem – the effects on public health of increased medical

malpractice insurance rates and the reluctance of qualified

physicians to practice here — by effectively increasing the

plaintiff’s burden of production in medical malpractice actions.

Given the critical substantive function that our common law

decisions have ascribed to expert testimony about the standard
27
of care, § 12-2604(A) is properly viewed as a modification of

that substantive common law, not merely as a change in

procedure.

B.

¶42 We therefore conclude that insofar as § 12-2604(A)

specifies the kind of expert testimony necessary to establish

medical malpractice, it is substantive in nature and does not

offend the separation of powers doctrine. Section 12-2604(A)

was enacted in 2005. 2005 Ariz. Sess. Laws, ch. 183, § 1 (1st

Reg. Sess.). This case was filed in 2004, and concerns conduct

occurring in 2002. Therefore, we must decide whether § 12-

2604(A) applies retroactively to actions filed before its

effective date.

¶43 “No statute is retroactive unless explicitly declared

therein.” A.R.S. § 1-244 (2002). Section 12-2604 contains no

such declaration. Arizona courts have “engrafted an exception”

to this statute under which a statute may nonetheless have

“retroactive effect if it is merely procedural.” In re Shane

B., 198 Ariz. at 87 ¶ 8, 7 P.3d at 96 (citation and internal

quotations omitted). We have today concluded that § 12-2604(A)

is not merely procedural. The statute therefore does not apply

retroactively to Seisinger’s claim.

28
 IV.

¶44 For the reasons above, we hold that § 12-2604(A) does

not violate the constitutional separation of powers doctrine.

We therefore vacate the opinion of the court of appeals. This

case does not present, and we today express no opinion, as to

whether the statute contravenes any other constitutional

provision. Because § 12-2604(A) does not apply retroactively,

we also vacate the judgment of the superior court and remand for

further proceedings consistent with this opinion.

_______________________________________
Andrew D. Hurwitz, Justice

CONCURRING:

_______________________________________
Rebecca White Berch, Vice Chief Justice

_______________________________________
Michael D. Ryan, Justice

_______________________________________
W. Scott Bales, Justice

E C K E R S T R O M, Judge, concurring in part and concurring in
the result.

¶45 I agree fully with the majority’s conclusions, set

forth in part II of the foregoing opinion: (1) that the Arizona
29
Constitution commands that the legislative, executive, and

judicial branches shall be “separate and distinct” and that no

branch “shall exercise the powers properly belonging to either

of the others,” Ariz. Const. art. 3; (2) that the Arizona

Constitution has expressly endowed the judiciary with the power

to promulgate “rules relative to all procedural matters in any

court,” id. art. 6, § 5(5); (3) that judicial rule-making power

generally includes the power to promulgate rules of evidence;

and (4) that the statute at issue here, A.R.S. § 12-2604(A),

conflicts with Arizona Rule of Evidence 702. I write separately

because, in this case, I cannot harmonize those premises with

the majority’s ultimate holding that § 12-2604(A) is

constitutional.

¶46 As Judge Irvine aptly observes in the court of appeals

opinion, “the separation of powers doctrine does not require

absolute compartmentalization of the branches.” Seisinger v.

Siebel, 219 Ariz. 163, ¶ 7, 195 P.3d 200, 202 (App. 2008). And,

as the majority’s scholarly opinion here chronicles, our

constitution tolerates each department’s incursion into the

other’s presumptive domain only so long as that incursion does

not conflict with, “or ‘tend[] to engulf,’” the power of the

constitutionally sanctioned branch. State ex rel. Napolitano v.

Brown, 194 Ariz. 340, ¶ 6, 982 P.2d 815, 817 (1999) (quoting

State v. Robinson, 153 Ariz. 191, 197, 735 P.2d 801, 807
30
(1987)). But when our legislature does enact a statute that

conflicts with a procedural rule promulgated by this Court, we

must determine which branch possesses the primary power, as set

forth in the Arizona Constitution, to address the topic at

issue. State v. Hansen, 215 Ariz. 287, ¶ 9, 160 P.3d 166, 168

(2007).

¶47 The Arizona Constitution endows the judicial

department with primary authority to create rules governing the

standards for the admissibility of evidence in an Arizona state

courtroom—at least when, as here, those rules pursue goals at

the core of the judicial function. As the majority

acknowledges, Article 6, Section 5(5) of the Arizona

Constitution expressly vests this Court with the “[p]ower to

make rules relative to all procedural matters in any court.”

And, this Court has repeatedly observed that, because the

Arizona Rules of Evidence are generally procedural in nature,

this Court’s authority to promulgate such rules ordinarily falls

within the power granted by that article. See, e.g., Barsema v.

Susong, 156 Ariz. 309, 314, 751 P.2d 969, 974 (1988); State v.

Robinson, 153 Ariz. 191, 197, 735 P.2d 801, 807 (1987);

Readenour v. Marion Power Shovel, 149 Ariz. 442, 444-45, 719

31
P.2d 1058, 1060-61 (1986); State ex rel. Collins v. Seidel, 142

Ariz. 587, 590, 691 P.2d 678, 681 (1984).9

¶48 But the authority of the judicial department over most

rules of evidence does not derive exclusively from its express

authority to promulgate procedural rules pursuant to Article 6,

Section 5(5), but also from the basic content of the “judicial

power” given to this department by our constitution in Article

6, Section 1. See Burney v. Lee, 59 Ariz. 360, 363-64, 129 P.2d

308, 309-10 (1942) (identifying rule-making authority as

“essentially judicial” in nature and inherent in court’s Article

6, Section 1 power). When addressing the constitutionality of a

statute conflicting with Arizona Rule of Evidence 802, this

Court has observed that the judiciary’s constitutional power to

promulgate hearsay rules derives both from “the reach of [the

Court’s] rulemaking authority” and the function of those rules

to pursue goals central to the judicial role. See Robinson, 153

_______________________________ 
9
As the majority correctly observes, judge-made substantive
law does not prevail over conflicting legislation merely because
this Court has characterized that law as a rule of evidence.
Specific rules of evidence that fall outside the domain of
plenary judicial power, as articulated by the Arizona
Constitution, are subordinate to conflicting legislation on the
same topic. See Valerie M. v. Ariz. Dep’t of Econ. Sec., 219
Ariz. 331, ¶ 21, 198 P.3d 1203, 1208 (2009). In the above-
referenced cases, however, this Court has repeatedly
acknowledged that most rules of evidence are fairly
characterized as procedural rather than substantive.

32
Ariz. at 197, 735 P.2d at 807. In that case, Justice Feldman

explained:

[T]he hearsay rules are at the core of the judicial
function: defining what is reliable evidence and
establishing judicial processes to test reliability.
Under basic separation of powers principles, these
judicial functions are separate and different from
legislative powers. As Professor Wigmore long ago
explained, “the judicial power involves the
application of the law to concrete facts and,
therefore, the investigation and establishment of the
facts. Any statute which prevents the judicial body
from ascertaining the [true] facts [in the case before
it] . . . is ineffective.”

Id. (alterations in original) (citation omitted). In so

reasoning, the court also observed that the enhancement of “the

truth-finding process” and rules designed to assure the

reliability of evidence presented stand at “the heart of the

judicial process.” Id.

¶49 Under the specific evidentiary rule at issue here,

Rule 702, expert testimony is admissible any time it “will

assist the trier of fact to understand the evidence or to

determine a fact in issue,” but only on condition that the

witness is “qualified as an expert by knowledge, skill,

experience, training, or education.” In this way, Rule 702 both

facilitates a party’s ability to establish facts relevant to the

proceedings and installs a threshold mechanism for ensuring that

such testimony is reliable.

33
¶50 The Court’s intention to pursue those twin goals in

promulgating Rule 702 is also evident in its prefatory note to

the section of the rules relating to expert witness testimony:

The rules in this article are designed to avoid
unnecessary restrictions concerning the admissibility
of opinion evidence; however, as this note makes
clear, an adverse attorney may, by timely objection,
invoke the court’s power to require that before
admission of an opinion there be a showing of the
traditional evidentiary prerequisites. Generally, it
is not intended that evidence which would have been
inadmissible under pre-existing law should now become
admissible.

Ariz. R. Evid. art. 7 note. Thus, in promulgating Rule 702,

this Court has sought to pursue goals that are central to the

judicial function—to create threshold standards for the

reliability of the testimony provided and assure an impartial

and rational process for each party to establish facts in a

courtroom. See also Ariz. R. Evid. 102 (identifying purpose of

Arizona Rules of Evidence as fair and efficient “development of

the law of evidence to the end that the truth may be ascertained

and proceedings justly determined”).10 In so doing, the Court

_______________________________ 
10
Arizona courts have yet to elaborate on what pursuits, if
any, might be characterized as core functions of the judiciary
beyond providing an efficient, reliable, and impartial truth-
finding process. But, to properly carry out the intent
expressed by our constitutional text in granting exclusively to
this department “[t]he judicial power,” Ariz. Const. art. 6,
§ 1, any such analysis would need to be securely tethered to
traditional notions of that power as reflected in conventional
understandings of institutional competence and judicial domain.
The majority may well be correct that articulating the precise

34
has exercised the judicial powers expressly conferred on this

department by both Sections 1 and 5(5) of Article 6 of the

Arizona Constitution.

¶51 For this reason, I must part ways with the majority’s

analytical approach and ultimate conclusion. If Rule 702 is

indeed an exercise of constitutionally endowed judicial power,

as authorized by both general and specific provisions of the

Arizona Constitution found in Article 6, it follows that a

statute addressing the same subject must constitute an improper

_________________________________ 
boundaries of the power bestowed by Article 6, Section 1 will be
difficult and may provide no greater analytical clarity than the
substantive/procedural framework suggested by the language of
Article 6, Section 5(5). But we cannot avoid considering the
language of Article 6, Section 1 merely because enforcing that
language might be analytically complex. And we do no service to
the legislative branch by overlooking that language. Indeed,
not all provisions of our rules of evidence would necessarily
advance a core judicial function and be protected from incursion
by the legislature. For example, traditional notions of the
judicial power would not support characterizing Arizona Rule of
Evidence 407 as an exercise of this Court’s plenary authority.
This is not because, as the majority suggests, the promulgation
of Rule 407 “reflects a substantive policy decision.” See n.5,
supra. All rules of evidence, even patently procedural ones,
reflect some form of policy decision—most often related, as
evidenced by the stated purpose of the rules, to providing an
efficient, reliable, and impartial truth-finding process.
Rather, Rule 407 falls outside of the primary domain of this
department because it addresses a concern (regarding subsequent
remedial measures) unrelated to core functions of the judiciary.
Put another way, it is indisputably a core function of the
judicial branch to create an impartial and efficient process for
presenting reliable evidence in a courtroom. It is not a core
judicial function to encourage property owners and manufacturers
to remedy dangerous conditions.

35
exercise of legislative authority to the extent the statute

conflicts with the rule. Put more succinctly, if the power to

determine the threshold for admissibility of expert testimony,

as set forth in Rule 702, properly belongs to the judicial

department, it cannot simultaneously belong to the legislature.

See Ariz. Const. art. 3 (dividing powers of government into

legislative, executive, and judicial departments and requiring

“such departments shall be separate and distinct, and no one of

such departments shall exercise the powers properly belonging to

either of the others”).

¶52 The majority does not directly dispute this fact, see

¶¶ 8-9, supra, but nonetheless performs a supplementary analysis

of whether the requirements set forth in § 12-2604(A) may be

characterized as “substantive or procedural.” See ¶ 24, supra.

In light of the clear answers provided by the text of the

Arizona Constitution when applied to Rule 702, I question the

necessity of engaging in that further analysis.

¶53 As discussed, this Court has repeatedly addressed the

constitutionality of statutes in purported conflict with

specific provisions of the Arizona Rules of Evidence. In each

of those cases, the Court has simply assumed, with brief

reference to the authority provided in Article 6, Section 5(5),

that the pertinent evidentiary rule fell squarely within the

judicial domain and that the statute would be unconstitutional
36
to the extent it conflicted with the rule. See Barsema, 156

Ariz. at 314, 751 P.2d at 974; Robinson, 153 Ariz. at 196-97,

735 P.2d at 806-07; Readenour, 149 Ariz. at 444-45, 719 P.2d at

1060-61; Seidel, 142 Ariz. at 590-91, 691 P.2d at 681-82. None

of those cases engaged in a supplementary and dispositive

analysis to confirm whether the statute’s content also could be

characterized as procedural. Only in Readenour did this Court

even mention the substantive/procedural dichotomy—noting that

the statute there had substantive and procedural features—and it

did so only in the context of explaining why the statute

harmonized rather than conflicted with the rule of evidence in

question there. 149 Ariz. at 446, 719 P.2d at 1062.

¶54 Thus, in apparent recognition of the fact that a power

cannot simultaneously belong to both branches, this Court has

declined to apply the procedural/substantive analysis to a

statute when such analysis is not necessary to resolve the

separation of powers question before it. Rather, it has

answered that question by determining whether the Court’s rule

of evidence falls within its grant of exclusive constitutional

authority and, if so, whether the statute conflicts with the

rule.11

_______________________________ 
11
In recognizing the logic of this approach, I do not suggest
that the separation of powers inquiry ends upon the discovery of
“some conflict between a validly enacted rule of evidence and a

37
¶55 The wisdom of this approach is aptly demonstrated by

the ease with which a statute setting forth an evidentiary rule

may be characterized as both substantive and procedural—and the

difficulty of determining which aspect controls. As the

majority observes and as this Court has previously acknowledged,

statutes relating to the admissibility of evidence “often have

both substantive and procedural aspects.” See ¶ 29, supra.

Presumably, then, we can only assess the fundamental nature of a

statute on this continuum by first identifying its respective

substantive and procedural features and then determining which

of those features are most relevant to the criteria

constitutionally provided for resolving separation of powers

problems.

¶56 Although the majority opinion cogently highlights what

it characterizes as the substantive aspects of § 12-2604(A), see

¶ 39, supra, it fails to identify or analyze the manifest

procedural features of that statute. To the extent our

jurisprudence has provided a yardstick for distinguishing
_________________________________ 
statute.” See ¶ 29, supra. Rather, once an evidentiary rule
has been determined to be an exercise of this Court’s plenary
authority as set forth by the various provisions of Article 6 of
the Arizona Constitution, then it follows that any conflicting
provision in a statute is unconstitutional. As the majority
correctly observes, a rule can be validly promulgated but
subordinate to any conflicting legislation if its promulgation
does not fall within the powers granted to the judicial branch
in Article 6. See ¶ 27, supra.

38
between substantive and procedural law, it has observed that

substantive law “creates, defines and regulates rights,” while

procedural law “prescribes the method of enforcing the right or

obtaining redress for its invasion.” State v. Birmingham, 96

Ariz. 109, 110, 392 P.2d 775, 776 (1964). Under that

definition, procedural law “pertains to . . . the practice,

method, procedure or legal machinery by which the substantive

law is enforced or made effective.” Id.

¶57 The majority declines to assess the procedural

features of § 12-2604(A) under the Birmingham test. But, in my

view, such an exercise provides considerable clarity in

assessing the essential nature of the statute. As a threshold

matter, § 12-2604(A) prescribes an evidentiary rule relating to

“an action alleging medical malpractice.” And there is no

dispute that the elements of that cause of action, because they

define the right to seek redress, are substantive law. But

§ 12-2604(A) does not create the right to sue when the elements

of that cause of action are met, nor does it specify what those

essential elements are: Those are set forth in part in A.R.S.

§ 12-563. Rather, § 12-2604(A) itemizes the qualifications an

expert witness must possess to present testimony on the standard

of care element found in § 12-563(1).

¶58 Thus, while § 12-563 sets forth substantive law by

specifying what must be proven, § 12-2604(A) prescribes the
39
method by which litigants must prove their entitlement to relief

under that substantive law. Under the traditional test

articulated in Birmingham, laws that provide “the method” for

asserting a specific substantive right are procedural in

nature.12 96 Ariz. at 110, 392 P.2d at 776.

¶59 The procedural aspect of § 12-2604(A) is highlighted

not only by our traditional approach to characterizing a

statute, but also by the function it performs in the context of

our evidentiary law. Neither the majority opinion nor any of

the litigants dispute that Rule 702 is procedural or that its

promulgation falls for that reason within the express delegation

of authority to the judiciary found in Article 6, Section 5(5).

To the extent the provisions of § 12-2604(A) conflict with Rule

702, as the majority opinion correctly concludes they do, those
_______________________________ 
12
The majority asks why the legislature may not “require a
heightened level of proof of the standard of care,” if the
legislature maintains the power to set forth the burden of proof
in the first instance. See ¶ 40, supra. But there remains an
analytical distinction under the Birmingham test between a
statute setting forth the quantum of proof necessary to support
a cause of action and a statute specifying what potential
witnesses may be used in doing so. Indeed, § 12-2604(A) does
not so much purport to address the level of proof as the form
that proof must take. For example, an experienced but recently
retired physician with all of the same academic qualifications
and practical experience as the defendant physician might well
be able to provide a very high level of proof for the plaintiff
on the question of the standard of care but would still be
disqualified from doing so by § 12-2604(A)(2)(a) and (3)(a),
which prohibit expert testimony if the witness no longer
maintains “active clinical practice.”

40
features of the statute must necessarily be procedural. And,

regardless of whether one ultimately concludes that the rule and

statute conflict, both specify preconditions for the

presentation of expert testimony in a court of law. Because

both perform essentially the same function, it makes little

sense to characterize one provision as procedural and the other

as substantive.13

¶60 At a minimum, then, the procedural features of § 12-

2604(A) are prominent. At the same time, the arguments for

characterizing the statute as substantive law are, in my

estimation, less persuasive. In essence, the majority posits

that elevated standards for the admission of expert testimony in

medical malpractice cases effectively establish an element of

the cause of action, “by specifying the kind of proof necessary

to meet the plaintiff’s burden of production.” See ¶ 38, supra.

But there are few, if any, rules of evidence that do not

similarly qualify the method by which claimants must meet their

burdens of production. Indeed, this is the function of those

rules. For example, the hearsay rules play this role in every
_______________________________ 
13
Although § 12-2604(A) addresses a particular element of a
particular cause of action—while Rule 702 applies broadly to all
causes of action—it makes little sense to conclude that the
legislature may constitutionally do in small increments what it
may not do in large ones. Certainly, no text in the Arizona
Constitution suggests such a basis for distinguishing
legislative and judicial domains.

41
case—rendering a certain type of information unavailable to

claimants to support the elements of their claim. Indeed, if

the Court were to apply this analytical approach in every case

addressing a conflict between a statute and a rule of evidence,

the statute must always prevail—and the legislature, not the

judicial department, would possess hegemony over all evidentiary

rules. Because such a shift of power stands in direct conflict

to the grant of authority to the judicial department found in

the text of the Arizona Constitution, I fear the majority’s

approach is incorrect and risks shifting the established

boundaries of judicial and legislative domains.

¶61 Although the majority’s characterization of § 12-

2604(A) as a constructive element of a medical malpractice cause

of action proves too much, I believe its second argument in

support of characterizing the statute as substantive, proves too

little. The majority observes correctly that this Court has

addressed standards for the admissibility of testimony on the

standard of care in medical malpractice cases, both before and

after it promulgated Rule 702. See ¶¶ 33-37, supra. And our

jurisprudence, like § 12-2604(A), has set threshold evidentiary

standards for the admissibility of such expert testimony higher

than those required by Rule 702. See ¶¶ 33-37, supra. The

majority then suggests that, because that jurisprudence has

evolved apart from the Arizona Rules of Evidence, it is
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presumptively substantive law, subject to legislative override.

See id.

¶62 However, as discussed, our constitutional text

expressly empowers the judicial department to “make rules

relative to all procedural matters.” Ariz. Const. art. 6,

§ 5(5). But it does not specify the method by which those rules

may be generated, developed, or promulgated. Indeed, as the

majority opinion acknowledges, this Court did not codify any

rules of evidence until 1977. See ¶ 35, supra. Thus, rules of

procedure do not become substantive law merely because they have

been articulated, explained, qualified, or amplified in case law

rather than in the text of a codified set of rules. Otherwise,

this Court would risk abdicating its express constitutional

rule-making authority every time it construes a question of

evidentiary, civil, juvenile, or criminal procedure in a

decision, a result our constitution simply does not contemplate.

¶63 In sum, the power to promulgate Rule 702 falls

squarely within the power allotted the judiciary by the general

and specific terms of Article 6 of the Arizona Constitution.

Because § 12-2604(A) conflicts with it, I would find that

statute to be an unconstitutional encroachment by the

legislature on the powers of this branch.

¶64 In so concluding, I am cognizant that the judiciary

must foster comity between the respective branches and that, in
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possessing the trust and responsibility to resolve disputes

among the branches including our own, we must be careful not to

develop self-serving and self-empowering approaches in analyzing

such questions. But we must also enforce the provisions of our

constitution that expressly grant the judiciary the primary

authority over those procedural rules that serve core judicial

functions. Because I fear the majority analysis fashions a

wholly new framework for addressing separation of powers

conflicts between statutes and evidentiary rules, and, in so

doing, shifts to the legislature power that constitutionally

belongs to this department, I can concur only in the result.

_________________________________
Peter J. Eckerstrom, Judge* 

_______________________________ 
*
Chief Justice Ruth V. McGregor has recused herself from
this case. Pursuant to Article 6, Section 3 of the Arizona
Constitution, the Honorable Peter J. Eckerstrom, Judge of the
Arizona Court of Appeals, Division Two, was designated to sit in
this matter.

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