06/28/93 DAUBERT et ux., individu v.
MERRELL DOW PHARMACEUTIC
BLUE BOOK CITATION FORM: 1993.SCT.130 (http://www.versuslaw.com)
[Editor's note: footnotes (if any) trail the opinion]
NOTE: Where it is feasible, a syllabus (headnote) will be released, as
is being done in connection with this case, at the time the opinion is
issued. The syllabus constitutes no part of the opinion of the Court but
has been prepared by the Reporter of Decisions for the convenience of
the reader. See United States v. Detroit Lumber Co., 200 U. S. 321, 337.
SUPREME COURT OF THE UNITED STATES
Syllabus
DAUBERT et ux., individually and as guardians and litem for DAUBERT,
et al.
v.
MERRELL DOW PHARMACEUTICALS, INC.
Certiorari to the United States Court of Appeals for the Ninth Circuit
No. 92-102.
Argued March 30, 1993
Decided June 28, 1993
Petitioners, two minor children and their parents, alleged in their suit
against respondent that the children's serious birth defects had been
caused by the mothers' prenatal ingestion of Bendectin, a prescription
drug marketed by respondent. The District Court granted respondent summary
judgment based on a well-credentialed expert's affidavit concluding, upon
reviewing the extensive published scientific literature on the subject,
that maternal use of Bendectin has not been shown to be a risk factor
for human birth defects. Although petitioners had responded with the testimony
of eight other well-credentialed experts, who based their conclusion that
Bendectin can cause birth defects on animal studies, chemical structure
analyses, and the unpublished ``reanalysis'' of previously published human
statistical studies, the court determined that this evidence did not meet
the applicable ``general acceptance'' standard for the admission of expert
testimony. The Court of Appeals agreed and affirmed, citing Frye v. United
States, 54 App. D. C. 46, 47, 293 F. 1013, 1014, for the rule that expert
opinion based on a scientific technique is inadmissible unless the technique
is ``generally accepted'' as reliable in the relevant scientific community.
Held: The Federal Rules of Evidence, not Frye, provide the standard for
admitting expert scientific testimony in a federal trial. Pp. 4-17.
(a) Frye's ``general acceptance'' test was superseded by the Rules' adoption.
The Rules occupy the field, United States v. Abel, 469 U. S. 45, 49, and,
although the common law of evidence may serve as an aid to their application,
id., at 51-52, respondent's assertion that they somehow assimilated Frye
is unconvincing. Nothing in the Rules as a whole or in the text and drafting
history of Rule 702, which specifically governs expert testimony, gives
any indication that ``general acceptance'' is a necessary precondition
to the admissibility of scientific evidence. Moreover, such a rigid standard
would be at odds with the Rules' liberal thrust and their general approach
of relaxing the traditional barriers to ``opinion'' testimony. Pp. 4-8.
(b) The Rules-especially Rule 702-place appropriate limits on the admissibility
of purportedly scientific evidence by assigning to the trial judge the
task of ensuring that an expert's testimony both rests on a reliable foundation
and is relevant to the task at hand. The reliability standard is established
by Rule 702's requirement that an expert's testimony pertain to ``scientific
. . . knowledge,'' since the adjective ``scientific'' implies a grounding
in science's methods and procedures, while the word ``knowledge'' connotes
a body of known facts or of ideas inferred from such facts or accepted
as true on good grounds. The Rule's requirement that the testimony ``assist
the trier of fact to understand the evidence or to determine a fact in
issue'' goes primarily to relevance by demanding a valid scientific connection
to the pertinent inquiry as a precondition to admissibility. Pp. 9-12.
(c) Faced with a proffer of expert scientific testimony under Rule 702,
the trial judge, pursuant to Rule 104(a), must make a preliminary assessment
of whether the testimony's underlying reasoning or methodology is scientifically
valid and properly can be applied to the facts at issue. Many considerations
will bear on the inquiry, including whether the theory or technique in
question can be (and has been) tested, whether it has been subjected to
peer review and publication, its known or potential error rate, and the
existence and maintenance of standards controlling its operation, and
whether it has attracted widespread acceptance within a relevant scientific
community. The inquiry is a flexible one, and its focus must be solely
on principles and methodology, not on the conclusions that they generate.
Throughout, the judge should also be mindful of other applicable Rules.
Pp. 12-15.
(d) Cross-examination, presentation of contrary evidence, and careful
instruction on the burden of proof, rather than wholesale exclusion under
an uncompromising ``general acceptance'' standard, is the appropriate
means by which evidence based on valid principles may be challenged. That
even limited screening by the trial judge, on occasion, will prevent the
jury from hearing of authentic scientific breakthroughs is simply a consequence
of the fact that the Rules are not designed to seek cosmic understanding
but, rather, to resolve legal disputes. Pp. 15-17. 951 F. 2d 1128, vacated
and remanded.
Blackmun, J., delivered the opinion for a unanimous Court with respect
to Parts I and II-A, and the opinion of the Court with respect to Parts
II-B, II-C, III, and IV, in which White, O'Connor, Scalia, Kennedy, Souter,
and Thomas, JJ., joined. Rehnquist, C. J., filed an opinion concurring
in part and dissenting in part, in which Stevens, J., joined.
NOTICE: This opinion is subject to formal revision before publication
in the preliminary print of the United States Reports. Readers are requested
to notify the Reporter of Decisions, Supreme Court of the United States,
Wash-ington, D.C. 20543, of any typographical or other formal errors,
in order that corrections may be made before the preliminary print goes
to press.
[1] SUPREME COURT OF THE UNITED STATES
[2] No. 92-102
[3] WILLIAM DAUBERT, et ux., etc., et al.,
[4] PETITIONERS
v.
[5] MERRELL DOW PHARMACEUTICALS, INC.
[6] On Writ of Certiorari to the United States Court of Appeals for the
Ninth Circuit
[7] [June 28, 1993]
[8] Justice Blackmun delivered the opinion of the Court.
[9] In this case we are called upon to determine the standard for admitting
expert scientific testimony in a federal trial.
I.
[10] Petitioners Jason Daubert and Eric Schuller are minor children born
with serious birth defects. They and their parents sued respondent in
California state court, alleging that the birth defects had been caused
by the mothers' ingestion of Bendectin, a prescription anti-nausea drug
marketed by respondent. Respondent removed the suits to federal court
on diversity grounds.
[11] After extensive discovery, respondent moved for summary judgment,
contending that Bendectin does not cause birth defects in humans and that
petitioners would be unable to come forward with any admissible evidence
that it does. In support of its motion, respondent submitted an affidavit
of Steven H. Lamm, physician and epidemiologist, who is a well-credentialed
expert on the risks from exposure to various chemical substances. *fn1
Doctor Lamm stated that he had reviewed all the literature on Bendectin
and human birth defects-more than 30 published studies involving over
130,000 patients. No study had found Bendectin to be a human teratogen
(i.e., a substance capable of causing malformations in fetuses). On the
basis of this review, Doctor Lamm concluded that maternal use of Bendectin
during the first trimester of pregnancy has not been shown to be a risk
factor for human birth defects.
[12] Petitioners did not (and do not) contest this characterization of
the published record regarding Bendectin. Instead, they responded to respondent's
motion with the testimony of eight experts of their own, each of whom
also possessed impressive credentials. *fn2 These experts had concluded
that Bendectin can cause birth defects. Their conclusions were based upon
"in vitro" (test tube) and "in vivo" (live) animal
studies that found a link between Bendectin and malformations; pharmacological
studies of the chemical structure of Bendectin that purported to show
similarities between the structure of the drug and that of other substances
known to cause birth defects; and the "reanalysis" of previously
published epidemiological (human statistical) studies.
[13] The District Court granted respondent's motion for summary judgment.
The court stated that scientific evidence is admissible only if the principle
upon which it is based is " `sufficiently established to have general
acceptance in the field to which it belongs.' " 727 F. Supp. 570,
572 (SD Cal. 1989), quoting United States v. Kilgus, 571 F. 2d 508, 510
(CA9 1978). The court concluded that petitioners' evidence did not meet
this standard. Given the vast body of epidemiological data concerning
Bendectin, the court held, expert opinion which is not based on epidemiological
evidence is not admissible to establish causation. 727 F. Supp., at 575.
Thus, the animal-cell studies, live-animal studies, and chemical-structure
analyses on which petitioners had relied could not raise by themselves
a reasonably disputable jury issue regarding causation. Ibid. Petitioners'
epidemiological analyses, based as they were on recalculations of data
in previously published studies that had found no causal link between
the drug and birth defects, were ruled to be inadmissible because they
had not been published or subjected to peer review. Ibid. 951 F.2d 1128
(1991). Citing Frye v. United States, 54 App. D.C. 46,
[14] The United States Court of Appeals for the Ninth Circuit affirmed.
47, 293 F. 1013, 1014 (1923), the court stated that expert opinion based
on a scientific technique is inadmissible unless the technique is "generally
accepted" as reliable in the relevant scientific community. 951 F.
2d, at 1129-1130. The court declared that expert opinion based on a methodology
that diverges "significantly from the procedures accepted by recognized
authorities in the field . . . cannot be shown to be `generally accepted
as a reliable technique.' " Id., at 1130, quoting United States v.
Solomon, 753 F. 2d 1522, 1526 (CA9 1985).
[15] The court emphasized that other Courts of Appeals considering the
risks of Bendectin had refused to admit reanalyses of epidemiological
studies that had been neither published nor subjected to peer review.
951 F. 2d, at 1130-1131. Those courts had found unpublished reanalyses
"particularly problematic in light of the massive weight of the original
published studies supporting [respondent's] position, all of which had
undergone full scrutiny from the scientific community." Id., at 1130.
Contending that reanalysis is generally accepted by the scientific community
only when it is subjected to verification and scrutiny by others in the
field, the Court of Appeals rejected petitioners' reanalyses as "unpublished,
not subjected to the normal peer review process and generated solely for
use in litigation." Id., at 1131. The court concluded that petitioners'
evidence provided an insufficient foundation to allow admission of expert
testimony that Bendectin caused their injuries and, accordingly, that
petitioners could not satisfy their burden of proving causation at trial.
[16] We granted certiorari, ___ U. S. ___ (1992), in light of sharp divisions
among the courts regarding the proper standard for the admission of expert
testimony. Compare, e. g., United States v. Shorter, 257 U. S. App. D.C.
358, 363-364, 809 F. 2d 54, 59-60 (applying the "general acceptance"
standard), cert. denied, 484 U. S. 817 (1987), with DeLuca v. Merrell
Dow Pharmaceuticals, Inc., 911 F. 2d 941, 955 (CA3 1990) (rejecting the
"general acceptance" standard).
II.
A.
[17] In the 70 years since its formulation in the Frye case, the "general
acceptance" test has been the dominant standard for determining the
admissibility of novel scientific evidence at trial. See E. Green &
C. Nesson, Problems, Cases, and Materials on Evidence 649 (1983). Although
under increasing attack of late, the rule continues to be followed by
a majority of courts, including the Ninth Circuit. *fn3
[18] The Frye test has its origin in a short and citation-free 1923 decision
concerning the admissibility of evidence derived from a systolic blood
pressure deception test, a crude precursor to the polygraph machine. In
what has become a famous (perhaps infamous) passage, the then Court of
Appeals for the District of Columbia described the device and its operation
and declared:
[19] "Just when a scientific principle or discovery crosses the
line between the experimental and demonstrable stages is difficult to
define. Somewhere in this twilight zone the evidential force of the principle
must be recognized, and while courts will go a long way in admitting expert
testimony deduced from a well-recognized scientific principle or discovery,
the thing from which the deduction is made must be sufficiently established
to have gained general acceptance in the particular field in which it
belongs." 54 App. D.C., at 47, 293 F., at 1014 (emphasis added).
[20] Because the deception test had "not yet gained such standing
and scientific recognition among physiological and psychological authorities
as would justify the courts in admitting expert testimony deduced from
the discovery, development, and experiments thus far made," evidence
of its results was ruled inadmissible. Ibid.
[21] The merits of the Frye test have been much debated, and scholarship
on its proper scope and application is legion. *fn4 Petitioners' primary
attack, however, is not on the content but on the continuing authority
of the rule. They contend that the Frye test was superseded by the adoption
of the Federal Rules of Evidence. *fn5 We agree.
[22] We interpret the legislatively-enacted Federal Rules of Evidence
as we would any statute. Beech Aircraft Corp. v. Rainey, 488 U. S. 153,
163 (1988). Rule 402 provides the baseline:
[23] "All relevant evidence is admissible, except as otherwise provided
by the Constitution of the United States, by Act of Congress, by these
rules, or by other rules prescribed by the Supreme Court pursuant to statutory
authority. Evidence which is not relevant is not admissible."
[24] "Relevant evidence" is defined as that which has "any
tendency to make the existence of any fact that is of consequence to the
determination of the action more probable or less probable than it would
be without the evidence." Rule 401. The Rule's basic standard of
relevance thus is a liberal one.
[25] Frye, of course, predated the Rules by half a century. In United
States v. Abel, 469 U. S. 45 (1984), we considered the pertinence of background
common law in interpreting the Rules of Evidence. We noted that the Rules
occupy the field, id., at 49, but, quoting Professor Cleary, the Reporter,
explained that the common law nevertheless could serve as an aid to their
application:
[26] "In principle, under the Federal Rules no common law of evidence
remains. `All relevant evidence is admissible, except as otherwise provided
. . . .' In reality, of course, the body of common law knowledge continues
to exist, though in the somewhat altered form of a source of guidance
in the exercise of delegated powers." Id., at 51-52.
[27] We found the common-law precept at issue in the Abel case entirely
consistent with Rule 402's general requirement of admissibility, and considered
it unlikely that the drafters had intended to change the rule. Id., at
50-51. In Bourjaily v. United States, 483 U. S. 171 (1987), on the other
hand, the Court was unable to find a particular common-law doctrine in
the Rules, and so held it superseded.
[28] Here there is a specific Rule that speaks to the contested issue.
Rule 702, governing expert testimony, provides:
[29] "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, experience,
training, or education, may testify thereto in the form of an opinion
or otherwise."
[30] Nothing in the text of this Rule establishes "general acceptance"
as an absolute prerequisite to admissibility. Nor does respondent present
any clear indication that Rule 702 or the Rules as a whole were intended
to incorporate a "general acceptance" standard. The drafting
history makes no mention of Frye, and a rigid "general acceptance"
requirement would be at odds with the "liberal thrust" of the
Federal Rules and their "general approach of relaxing the traditional
barriers to `opinion' testimony." Beech Aircraft Corp. v. Rainey,
488 U. S., at 169 (citing Rules 701 to 705). See also Weinstein, Rule
702 of the Federal Rules of Evidence is Sound; It Should Not Be Amended,
138 F.R.D. 631, 631 (1991) ("The Rules were designed to depend primarily
upon lawyer-adversaries and sensible triers of fact to evaluate conflicts").
Given the Rules' permissive backdrop and their inclusion of a specific
rule on expert testimony that does not mention "general acceptance,"
the assertion that the Rules somehow assimilated Frye is unconvincing.
Frye made `general acceptance' the exclusive test for admitting expert
scientific testimony. That austere standard, absent from and incompatible
with the Federal Rules of Evidence, should not be applied in federal trials.
*fn6
B.
[31] That the Frye test was displaced by the Rules of Evidence does not
mean, however, that the Rules themselves place no limits on the admissibility
of purportedly scientific evidence. *fn7 Nor is the trial judge disabled
from screening such evidence. To the contrary, under the Rules the trial
judge must ensure that any and all scientific testimony or evidence admitted
is not only relevant, but reliable.
[32] The primary locus of this obligation is Rule 702, which clearly
contemplates some degree of regulation of the subjects and theories about
which an expert may testify. "If scientific, technical, or other
specialized knowledge will assist the trier of fact to understand the
evidence or to determine a fact in issue" an expert "may testify
thereto." The subject of an expert's testimony must be "scientific
. . . knowledge." *fn8 The adjective "scientific" implies
a grounding in the methods and procedures of science. Similarly, the word
"knowledge" connotes more than subjective belief or unsupported
speculation. The term "applies to any body of known facts or to any
body of ideas inferred from such facts or accepted as truths on good grounds."
Webster's Third New International Dictionary 1252 (1986). Of course, it
would be unreasonable to conclude that the subject of scientific testimony
must be "known" to a certainty; arguably, there are no certainties
in science. See, e. g., Brief for Nicolaas Bloembergen et al. as Amici
Curiae 9 ("Indeed, scientists do not assert that they know what is
immutably `true'-they are committed to searching for new, temporary theories
to explain, as best they can, phenomena"); Brief for American Association
for the Advancement of Science and the National Academy of Sciences as
Amici Curiae 7-8 ("Science is not an encyclopedic body of knowledge
about the universe. Instead, it represents a process for proposing and
refining theoretical explanations about the world that are subject to
further testing and refinement") (emphasis in original). But, in
order to qualify as "scientific knowledge," an inference or
assertion must be derived by the scientific method. Proposed testimony
must be supported by appropriate validation-i.e., "good grounds,"
based on what is known. In short, the requirement that an expert's testimony
pertain to "scientific knowledge" establishes a standard of
evidentiary reliability. *fn9
[33] Rule 702 further requires that the evidence or testimony "assist
the trier of fact to understand the evidence or to determine a fact in
issue." This condition goes primarily to relevance. "Expert
testimony which does not relate to any issue in the case is not relevant
and, ergo, non-helpful." 3 Weinstein & Berger Para(s) 702[02],
p. 702-18. See also United States v. Downing, 753 F. 2d 1224, 1242 (CA3
1985) ("An additional consideration under Rule 702-and another aspect
of relevancy-is whether expert testimony proffered in the case is sufficiently
tied to the facts of the case that it will aid the jury in resolving a
factual dispute"). The consideration has been aptly described by
Judge Becker as one of "fit." Ibid. "Fit" is not always
obvious, and scientific validity for one purpose is not necessarily scientific
validity for other, unrelated purposes. See Starrs, Frye v. United States
Restructured and Revitalized: A Proposal to Amend Federal Evidence Rule
702, and 26 Jurimetrics J. 249, 258 (1986). The study of the phases of
the moon, for example, may provide valid scientific "knowledge"
about whether a certain night was dark, and if darkness is a fact in issue,
the knowledge will assist the trier of fact. However (absent creditable
grounds supporting such a link), evidence that the moon was full on a
certain night will not assist the trier of fact in determining whether
an individual was unusually likely to have behaved irrationally on that
night. Rule 702's "helpfulness" standard requires a valid scientific
connection to the pertinent inquiry as a precondition to admissibility.
[34] That these requirements are embodied in Rule 702 is not surprising.
Unlike an ordinary witness, see Rule 701, an expert is permitted wide
latitude to offer opinions, including those that are not based on first-hand
knowledge or observation. See Rules 702 and 703. Presumably, this relaxation
of the usual requirement of first-hand knowledge-a rule which represents
"a `most pervasive manifestation' of the common law insistence upon
`the most reliable sources of information,' " Advisory Committee's
Notes on Fed. Rule Evid. 602 (citation omitted)-is premised on an assumption
that the expert's opinion will have a reliable basis in the knowledge
and experience of his discipline.
C.
[35] Faced with a proffer of expert scientific testimony, then, the trial
judge must determine at the outset, pursuant to Rule 104(a), *fn10 whether
the expert is proposing to testify to (1) scientific knowledge that (2)
will assist the trier of fact to understand or determine a fact in issue.
*fn11 This entails a preliminary assessment of whether the reasoning or
methodology underlying the testimony is scientifically valid and of whether
that reasoning or methodology properly can be applied to the facts in
issue. We are confident that federal judges possess the capacity to undertake
this review. Many factors will bear on the inquiry, and we do not presume
to set out a definitive checklist or test. But some general observations
are appropriate.
[36] Ordinarily, a key question to be answered in determining whether
a theory or technique is scientific knowledge that will assist the trier
of fact will be whether it can be (and has been) tested. "Scientific
methodology today is based on generating hypotheses and testing them to
see if they can be falsified; indeed, this methodology is what distinguishes
science from other fields of human inquiry." Green, at 645. See also
C. Hempel, Philosophy of Natural Science 49 (1966) ("[T]he statements
constituting a scientific explanation must be capable of empirical test");
K. Popper, Conjectures and Refutations: The Growth of Scientific Knowledge
37 (5th ed. 1989) ("[T]he criterion of the scientific status of a
theory is its falsifiability, or refutability, or testability").
[37] Another pertinent consideration is whether the theory or technique
has been subjected to peer review and publication. Publication (which
is but one element of peer review) is not a sine qua non of admissibility;
it does not necessarily correlate with reliability, see S. Jasanoff, The
Fifth Branch: Science Advisors as Policymakers 61-76 (1990), and in some
instances well-grounded but innovative theories will not have been published,
see Horrobin, The Philosophical Basis of Peer Review and the Suppression
of Innovation, 263 J. Am. Med. Assn. 1438 (1990). Some propositions, moreover,
are too particular, too new, or of too limited interest to be published.
But submission to the scrutiny of the scientific community is a component
of "good science," in part because it increases the likelihood
that substantive flaws in methodology will be detected. See J. Ziman,
Reliable Knowledge: An Exploration of the Grounds for Belief in Science
130-133 (1978); Relman and Angell, How Good Is Peer Review?, 321 New Eng.
J. Med. 827 (1989). The fact of publication (or lack thereof) in a peer-reviewed
journal thus will be a relevant, though not dispositive, consideration
in assessing the scientific validity of a particular technique or methodology
on which an opinion is premised.
[38] Additionally, in the case of a particular scientific technique,
the court ordinarily should consider the known or potential rate of error,
see, e. g., United States v. Smith, 869 F. 2d 348, 353-354 (CA7 1989)
(surveying studies of the error rate of spectrographic voice identification
technique), and the existence and maintenance of standards controlling
the technique's operation. See United States v. Williams, 583 F. 2d 1194,
1198 (CA2 1978) (noting professional organization's standard governing
spectrographic analysis), cert. denied, 439 U. S. 1117 (1979).
[39] Finally, "general acceptance" can yet have a bearing on
the inquiry. A "reliability assessment does not require, although
it does permit, explicit identification of a relevant scientific community
and an express determination of a particular degree of acceptance within
that community." United States v. Downing, 753 F. 2d, at 1238. See
also 3 Weinstein & Berger Para(s) 702[03], pp. 702-41 to 702-42. Widespread
acceptance can be an important factor in ruling particular evidence admissible,
and "a known technique that has been able to attract only minimal
support within the community," Downing, supra, at 1238, may properly
be viewed with skepticism.
[40] The inquiry envisioned by Rule 702 is, we emphasize, a flexible
one. *fn12 Its overarching subject is the scientific validity-and thus
the evidentiary relevance and reliability-of the principles that underlie
a proposed submission. The focus, of course, must be solely on principles
and methodology, not on the conclusions that they generate.
[41] Throughout, a judge assessing a proffer of expert scientific testimony
under Rule 702 should also be mindful of other applicable rules. Rule
703 provides that expert opinions based on otherwise inadmissible hearsay
are to be admitted only if the facts or data are "of a type reasonably
relied upon by experts in the particular field in forming opinions or
inferences upon the subject." Rule 706 allows the court at its discretion
to procure the assistance of an expert of its own choosing. Finally, Rule
403 permits the exclusion of relevant evidence "if its probative
value is substantially outweighed by the danger of unfair prejudice, confusion
of the issues, or misleading the jury . . . ." Judge Weinstein has
explained: "Expert evidence can be both powerful and quite misleading
because of the difficulty in evaluating it. Because of this risk, the
judge in weighing possible prejudice against probative force under Rule
403 of the present rules exercises more control over experts than over
lay witnesses." Weinstein, 138 F.R.D., at 632.
III.
[42] We conclude by briefly addressing what appear to be two underlying
concerns of the parties and amici in this case. Respondent expresses apprehension
that abandonment of "general acceptance" as the exclusive requirement
for admission will result in a "free-for-all" in which befuddled
juries are confounded by absurd and irrational pseudoscientific assertions.
In this regard respondent seems to us to be overly pessimistic about the
capabilities of the jury, and of the adversary system generally. Vigorous
cross-examination, presentation of contrary evidence, and careful instruction
on the burden of proof are the traditional and appropriate means of attacking
shaky but admissible evidence. See Rock v. Arkansas, 483 U. S. 44, 61
(1987). Additionally, in the event the trial court concludes that the
scintilla of evidence presented supporting a position is insufficient
to allow a reasonable juror to conclude that the position more likely
than not is true, the court remains free to direct a judgment, Fed. Rule
Civ. Proc. 50 (a), and likewise to grant summary judgment, Fed. Rule Civ.
Proc. 56. Cf., e.g., Turpin v. Merrell Dow Pharmaceuticals, Inc., 959
F. 2d 1349 (CA6) (holding that scientific evidence that provided foundation
for expert testimony, viewed in the light most favorable to plaintiffs,
was not sufficient to allow a jury to find it more probable than not that
defendant caused plaintiff's injury), cert. denied, 506 U. S. ___ (1992);
Brock v. Merrell Dow Pharmaceuticals, Inc., 874 F. 2d 307 (CA5 1989) (reversing
judgment entered on jury verdict for plaintiffs because evidence regarding
causation was insufficient), modified, 884 F. 2d 166 (CA5 1989), cert.
denied, 494 U. S. 1046 (1990); Green 680-681. These conventional devices,
rather than wholesale exclusion under an uncompromising "general
acceptance" test, are the appropriate safeguards where the basis
of scientific testimony meets the standards of Rule 702.
[43] Petitioners and, to a greater extent, their amici exhibit a different
concern. They suggest that recognition of a screening role for the judge
that allows for the exclusion of "invalid" evidence will sanction
a stifling and repressive scientific orthodoxy and will be inimical to
the search for truth. See, e.g., Brief for Ronald Bayer et al. as Amici
Curiae. It is true that open debate is an essential part of both legal
and scientific analyses. Yet there are important differences between the
quest for truth in the courtroom and the quest for truth in the laboratory.
Scientific conclusions are subject to perpetual revision. Law, on the
other hand, must resolve disputes finally and quickly. The scientific
project is advanced by broad and wide-ranging consideration of a multitude
of hypotheses, for those that are incorrect will eventually be shown to
be so, and that in itself is an advance. Conjectures that are probably
wrong are of little use, however, in the project of reaching a quick,
final, and binding legal judgment-often of great consequence-about a particular
set of events in the past. We recognize that in practice, a gatekeeping
role for the judge, no matter how flexible, inevitably on occasion will
prevent the jury from learning of authentic insights and innovations.
That, nevertheless, is the balance that is struck by Rules of Evidence
designed not for the exhaustive search for cosmic understanding but for
the particularized resolution of legal disputes. *fn13
IV.
[44] To summarize: "general acceptance" is not a necessary
precondition to the admissibility of scientific evidence under the Federal
Rules of Evidence, but the Rules of Evidence-especially Rule 702-do assign
to the trial judge the task of ensuring that an expert's testimony both
rests on a reliable foundation and is relevant to the task at hand. Pertinent
evidence based on scientifically valid principles will satisfy those demands.
[45] The inquiries of the District Court and the Court of Appeals focused
almost exclusively on "general acceptance," as gauged by publication
and the decisions of other courts. Accordingly, the judgment of the Court
of Appeals is vacated and the case is remanded for further proceedings
consistent with this opinion.
[46] It is so ordered.
[47] Chief Justice Rehnquist, with whom Justice Stevens joins, concurring
in part and dissenting in part.
[48] The petition for certiorari in this case presents two questions:
first, whether the rule of Frye v. United States, 54 App. D. C. 46, 293
F. 1013 (1923), remains good law after the enactment of the Federal Rules
of Evidence; and second, if Frye remains valid, whether it requires expert
scientific testimony to have been subjected to a peer-review process in
order to be admissible. The Court concludes, correctly in my view, that
the Frye rule did not survive the enactment of the Federal Rules of Evidence,
and I therefore join Parts I and II-A of its opinion. The second question
presented in the petition for certiorari necessarily is mooted by this
holding, but the Court nonetheless proceeds to construe Rules 702 and
703 very much in the abstract, and then offers some "general observations."
Ante, at 12.
[49] "General observations" by this Court customarily carry
great weight with lower federal courts, but the ones offered here suffer
from the flaw common to most such observations-they are not applied to
deciding whether or not particular testimony was or was not admissible,
and therefore they tend to be not only general, but vague and abstract.
This is particularly unfortunate in a case such as this, where the ultimate
legal question depends on an appreciation of one or more bodies of knowledge
not judicially noticeable, and subject to different interpretations in
the briefs of the parties and their amici. Twenty-two amicus briefs have
been filed in the case, and indeed the Court's opinion contains no less
than 37 citations to amicus briefs and other secondary sources.
[50] The various briefs filed in this case are markedly different from
typical briefs, in that large parts of them do not deal with decided cases
or statutory language-the sort of material we customarily interpret. Instead,
they deal with definitions of scientific knowledge, scientific method,
scientific validity, and peer review-in short, matters far afield from
the expertise of judges. This is not to say that such materials are not
useful or even necessary in deciding how Rule 703 should be applied; but
it is to say that the unusual subject matter should cause us to proceed
with great caution in deciding more than we have to, because our reach
can so easily exceed our grasp.
[51] But even if it were desirable to make "general observations"
not necessary to decide the questions presented, I cannot subscribe to
some of the observations made by the Court. In Part II-B, the Court concludes
that reliability and relevancy are the touchstones of the admissibility
of expert testimony. Ante, at 9. Federal Rule of Evidence 402 provides,
as the Court points out, that "[e]vidence which is not relevant is
not admissible." But there is no similar reference in the Rule to
"reliability." The Court constructs its argument by parsing
the language "[i]f scientific, technical, or other specialized knowledge
will assist the trier of fact to understand the evidence or to determine
a fact in issue . . . an expert . . . may testify thereto . . . ."
Fed. Rule Evid. 702. It stresses that the subject of the expert's testimony
must be "scientific . . . knowledge," and points out that "scientific"
"implies a grounding in the methods and procedures of science,"
and that the word "knowledge" "connotes more than subjective
belief or unsupported speculation." Ante, at 9. From this it concludes
that "scientific knowledge" must be "derived by the scientific
method." Ante, at 10. Proposed testimony, we are told, must be supported
by "appropriate validation." Ante, at 10. Indeed, in footnote
9, the Court decides that "[i]n a case involving scientific evidence,
evidentiary reliability will be based upon scientific validity."
Ante, at 10, n. 9 (emphasis in original).
[52] Questions arise simply from reading this part of the Court's opinion,
and countless more questions will surely arise when hundreds of district
judges try to apply its teaching to particular offers of expert testimony.
Does all of this dicta apply to an expert seeking to testify on the basis
of "technical or other specialized knowledge"-the other types
of expert knowledge to which Rule 702 applies-or are the "general
observations" limited only to "scientific knowledge" ?
What is the difference between scientific knowledge and technical knowledge;
does Rule 702 actually contemplate that the phrase "scientific, technical,
or other specialized knowledge" be broken down into numerous subspecies
of expertise, or did its authors simply pick general descriptive language
covering the sort of expert testimony which courts have customarily received?
The Court speaks of its confidence that federal judges can make a "preliminary
assessment of whether the reasoning or methodology underlying the testimony
is scientifically valid and of whether that reasoning or methodology properly
can be applied to the facts in issue." Ante, at 12. The Court then
states that a "key question" to be answered in deciding whether
something is "scientific knowledge" "will be whether it
can be (and has been) tested." Ante, at 12. Following this sentence
are three quotations from treatises, which speak not only of empirical
testing, but one of which states that "the criterion of the scientific
status of a theory is its falsifiability, or refutability, or testability,"
ante, pp. 12-13.
[53] I defer to no one in my confidence in federal judges; but I am at
a loss to know what is meant when it is said that the scientific status
of a theory depends on its "falsifiability," and I suspect some
of them will be, too.
[54] I do not doubt that Rule 702 confides to the judge some gatekeeping
responsibility in deciding questions of the admissibility of proffered
expert testimony. But I do not think it imposes on them either the obligation
or the authority to become amateur scientists in order to perform that
role. I think the Court would be far better advised in this case to decide
only the questions presented, and to leave the further development of
this important area of the law to future cases.
***** BEGIN FOOTNOTE(S) HERE *****
[55] *fn1 Doctor Lamm received his master's and doctor of medicine degrees
from the University of Southern California. He has served as a consultant
in birth-defect epidemiology for the National Center for Health Statistics
and has published numerous articles on the magnitude of risk from exposure
to various chemical and biological substances. App. 34-44.
[56] *fn2 For example, Shanna Helen Swan, who received a master's degree
in biostatics from Columbia University and a doctorate in statistics from
the University of California at Berkeley, is chief of the section of the
California Department of Health and Services that determines causes of
birth defects, and has served as a consultant to the World Health Organization,
the Food and Drug Administration, and the National Institutes of Health.
App. 113-114, 131-132. Stewart A. Newman, who received his master's and
a doctorate in chemistry from Columbia University and the University of
Chicago, respectively, is a professor at New York Medical College and
has spent over a decade studying the effect of chemicals on limb development.
App. 54-56. The credentials of the others are similarly impressive. See
App. 61-66, 73-80, 148-153, 187-192, and Attachment to Petitioners' Opposition
to Summary Judgment, Tabs 12, 20, 21, 26, 31, 32.
[57] *fn3 For a catalogue of the many cases on either side of this controversy,
see P. Gianelli & E. Imwinkelried, Scientific Evidence 1-5, pp. 10-14
(1986 & Supp. 1991).
[58] *fn4 See, e. g., Green, Expert Witnesses and Sufficiency of Evidence
in Toxic Substances Litigation: The Legacy of Agent Orange and Bendectin
Litigation, 86 Nw. U. L. Rev. 643 (1992) (hereinafter Green); Becker &
Orenstein, The Federal Rules of Evidence After Sixteen Years-The Effect
of "Plain Meaning" Jurisprudence, the Need for an Advisory Committee
on the Rules of Evidence, and Suggestions for Selective Revision of the
Rules, 60 Geo. Wash.L.Rev. 857, 876-885 (1992); Hanson, "James Alphonso
Frye is Sixty-Five Years Old; Should He Retire?," 16 W. St. U. L.
Rev. 357 (1989); Black, A Unified Theory of Scientific Evidence, 56 Ford.
L. Rev. 595 (1988); Imwinkelried, The "Bases" of Expert Testimony:
The Syllogistic Structure of Scientific Testimony, 67 N.C. L. Rev. 1 (1988);
Proposals for a Model Rule on the Admissibility of Scientific Evidence,
26 Jurimetrics J. 235 (1986); Gianelli, The Admissibility of Novel Scientific
Evidence: Frye v. United States, A Half-Century Later, 80 Colum. L. Rev.
1197 (1980); The Supreme Court, 1986 Term, 101 Harv. L. Rev. 7, 119, 125-127
(1987).
[59] Indeed, the debates over Frye are such a well-established part of
the academic landscape that a distinct term-"Frye-ologist"-has
been advanced to describe those who take part. See Behringer, Introduction,
Proposals for a Model Rule on the Admissibility of Scientific Evidence,
26 Jurimetrics J., at 239, quoting Lacey, Scientific Evidence, 24 Jurimetrics
J. 254, 264 (1984).
[60] *fn5 Like the question of Frye's merit, the dispute over its survival
has divided courts and commentators. Compare, e. g., United States v.
Williams, 583 F. 2d 1194 (CA2 1978), cert. denied, 439 U. S. 1117 (1979)
(Frye is superseded by the Rules of Evidence), with Christopherson v.
Allied-Signal Corp., 939 F. 2d 1106, 1111, 1115-1116 (CA5 1991) (en banc)
(Frye and the Rules coexist), cert. denied, ___ U. S. ___ (1992), 3 J.
Weinstein & M. Berger, Weinstein's Evidence Para(s) 702[03], pp. 702-36
to 702-37 (1988) (hereinafter Weinstein & Berger) (Frye is dead),
and M. Graham, Handbook of Federal Evidence Section(s) 703.2 (2d ed. 1991)
(Frye lives). See generally P. Gianelli & E. Imwinkelried, Scientific
Evidence Section(s) 1-5, pp. 28-29 (1986 & Supp. 1991) (citing authorities).
[61] *fn6 Because we hold that Frye has been superseded and base the
discussion that follows on the content of the congressionally-enacted
Federal Rules of Evidence, we do not address petitioners' argument that
application of the Frye rule in this diversity case, as the application
of a judge-made rule affecting substantive rights, would violate the doctrine
of Erie R. Co. v. Tompkins, 304 U. S. 64 (1938).
[62] *fn7 The Chief Justice "do[es] not doubt that Rule 702 confides
to the judge some gatekeeping responsibility," post, at 4, but would
neither say how it does so, nor explain what that role entails. We believe
the better course is to note the nature and source of the duty.
[63] *fn8 Rule 702 also applies to "technical, or other specialized
knowledge." Our discussion is limited to the scientific context because
that is the nature of the expertise offered here.
[64] *fn9 We note that scientists typically distinguish between "validity"
(does the principle support what it purports to show?) and "reliability"
(does application of the principle produce consistent results?). See Black,
A Unified Theory of Scientific Evidence, 56 Ford. L. Rev. 595, 599 (1988).
Although "the difference between accuracy, validity, and reliability
may be such that each is distinct from the other by no more than a hen's
kick," Starrs, Frye v. United States Restructured and Revitalized:
A Proposal to Amend Federal Evidence Rule 702, 26 Jurimetrics J. 249,
256 (1986), our reference here is to evidentiary reliability-that is,
trustworthiness. Cf., e. g., Advisory Committee's Notes on Fed. Rule Evid.
602 (" `[T]he rule requiring that a witness who testifies to a fact
which can be perceived by the senses must have had an opportunity to observe,
and must have actually observed the fact' is a `most pervasive manifestation'
of the common law insistence upon 'the most reliable sources of information.'
" (citation omitted)); Advisory Committee's Notes on Art. VIII of
the Rules of Evidence (hearsay exceptions will be recognized only "under
circumstances supposed to furnish guarantees of trustworthiness").
In a case involving scientific evidence, evidentiary reliability will
be based upon scientific validity.
[65] *fn10 Rule 104(a) provides:
[66] "Preliminary questions concerning the qualification of a person
to be a witness, the existence of a privilege, or the admissibility of
evidence shall be determined by the court, subject to the provisions of
subdivision (b) [pertaining to conditional admissions]. In making its
determination it is not bound by the rules of evidence except those with
respect to privileges." These matters should be established by a
preponderance of proof. See Bourjaily v. United States, 483 U. S. 171,
175-176 (1987).
[67] *fn11 Although the Frye decision itself focused exclusively on "novel"
scientific techniques, we do not read the requirements of Rule 702 to
apply specially or exclusively to unconventional evidence. Of course,
well-established propositions are less likely to be challenged than those
that are novel, and they are more handily defended. Indeed, theories that
are so firmly established as to have attained the status of scientific
law, such as the laws of thermodynamics, properly are subject to judicial
notice under Fed. Rule Evid. 201.
[68] *fn12 A number of authorities have presented variations on the reliability
approach, each with its own slightly different set of factors. See, e.
g., Downing, 753 F. 2d 1238-1239 (on which our discussion draws in part);
3 Weinstein & Berger Para(s) 702[03], pp. 702-41 to 702-42 (on which
the Downing court in turn partially relied); McCormick, Scientific Evidence:
Defining a New Approach to Admissibility, 67 Iowa L. Rev. 879, 911-912
(1982); and Symposium on Science and the Rules of Evidence, 99 F.R.D.
187, 231 (1983) (statement by Margaret Berger). To the extent that they
focus on the reliability of evidence as ensured by the scientific validity
of its underlying principles, all these versions may well have merit,
although we express no opinion regarding any of their particular details.
[69] *fn13 This is not to say that judicial interpretation, as opposed
to adjudicative factfinding, does not share basic characteristics of the
scientific endeavor: "The work of a judge is in one sense enduring
and in another ephemeral. . . . In the endless process of testing and
retesting, there is a constant rejection of the dross and a constant retention
of whatever is pure and sound and fine." B. Cardozo, The Nature of
the Judicial Process 178, 179 (1921).
***** END FOOTNOTE(S) HERE *****
[Editor's note: Illustrations from the original opinion, if any, are
available in the print version]
Copyright 1993 VersusLaw, Inc., (206) 250-0142 http://www.versuslaw.com
19930628
1993.SCT.130
|