OCTOBER TERM, 1997
Syllabus
GENERAL ELECTRIC CO. ET AL.
v. JOINER ET ux.
CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE
ELEVENTH CIRCUIT
No. 96-188. Argued October 14, 1997-Decided December 15,1997
After he was diagnosed with small-cell lung cancer, respondent
Joiner and his wife (hereinafter jointly respondent) sued in
Georgia state court, alleging,
inter alia, that his disease
was "promoted" by his workplace exposure to chemical "PCB's" and
derivative "furans" and "dioxins" that were manufactured by, or
present in materials manufactured by, petitioners. Petitioners
removed the case to federal court and moved for summary judgment.
Joiner responded with the depositions of expert witnesses, who
testified that PCB's, furans, and dioxins can promote cancer, and
opined that Joiner's exposure to those chemicals was likely
responsible for his cancer. The District Court ruled that there was
a genuine issue of material fact as to whether Joiner had been
exposed to PCB's, but granted summary judgment for petitioners
because (1) there was no genuine issue as to whether he had been
exposed to furans and dioxins, and (2) his experts' testimony had
failed to show that there was a link between exposure to PCB's and
small-cell lung cancer and was therefore inadmissible because it
did not rise above "subjective belief or unsupported speculation."
In reversing, the Eleventh Circuit applied "a particularly
stringent standard of review" to hold that the District Court had
erred in excluding the expert testimony.
Held:
1. Abuse of discretion-the standard ordinarily applicable to
review of evidentiary rulings-is the proper standard by which to
review a district court's decision to admit or exclude expert
scientific evidence. Contrary to the Eleventh Circuit's suggestion,
Daubert v.
Merrell Dow Pharmaceuticals, Inc.,
509 U. S. 579,
did not somehow alter this general rule in the context of a
district court's decision to exclude scientific evidence.
Daubert did not address the appellate review standard for
evidentiary rulings at all, but did indicate that, while the
Federal Rules of Evidence allow district courts to admit a somewhat
broader range of scientific testimony than did pre-existing law,
they leave in place the trial judge's "gatekeeper" role of
screening such evidence to ensure that it is not only relevant, but
reliable.
Id., at 589. A court of appeals applying
"abuse-of-discretion" review to such rulings may not categorically
distinguish between rulings allowing expert testimony and rulings
which disallow it. Compare
Beech Aircraft Corp. v.
Rainey, 488 U. S.
137
153,172, with
United States v.
Abel, 469 U. S. 45, 54. This
Court rejects Joiner's argument that because the granting of
summary judgment in this case was "outcome determinative," it
should have been subjected to a more searching standard of review.
On a summary judgment motion, disputed issues of fact are resolved
against the moving party-here, petitioners. But the question of
admissibility of expert testimony is not such an issue of fact, and
is reviewable under the abuse-of-discretion standard. In applying
an overly "stringent" standard, the Eleventh Circuit failed to give
the trial court the deference that is the hallmark of
abuse-of-discretion review. Pp. 141-143.
2. A proper application of the correct standard of review
indicates that the District Court did not err in excluding the
expert testimony at issue. The animal studies cited by respondent's
experts were so dissimilar to the facts presented here-i.
e., the studies involved infant mice that developed
alveologenic adenomas after highly concentrated, massive doses of
PCB's were injected directly into their peritoneums or stomachs,
whereas Joiner was an adult human whose small-cell carcinomas
allegedly resulted from exposure on a much smaller scale-that it
was not an abuse of discretion for the District Court to have
rejected the experts' reliance on those studies. Nor did the court
abuse its discretion in concluding that the four epidemiological
studies on which Joiner relied were not a sufficient basis for the
experts' opinions, since the authors of two of those studies
ultimately were unwilling to suggest a link between increases in
lung cancer and PCB exposure among the workers they examined, the
third study involved exposure to a particular type of mineral oil
not necessarily relevant here, and the fourth involved exposure to
numerous potential carcinogens in addition to PCB's. Nothing in
either
Daubert or the Federal Rules of Evidence requires a
district court to admit opinion evidence that is connected to
existing data only by the
ipse dixit of the expert. Pp.
143-147.
3. These conclusions, however, do not dispose of the entire
case. The Eleventh Circuit reversed the District Court's conclusion
that Joiner had not been exposed to furans and dioxins. Because
petitioners did not challenge that determination in their
certiorari petition, the question whether exposure to furans and
dioxins contributed to Joiner's cancer is still open. P. 147.
78 F.3d
524, reversed and remanded.
REHNQUIST, C. J., delivered the opinion for a unanimous Court
with respect to Parts I and II, and the opinion of the Court with
respect to Part III, in which O'CONNOR, SCALIA, KENNEDY, SOUTER,
THOMAS, GINSBURG, and BREYER, JJ., joined. BREYER, J., filed a
concurring opinion,
138
post, p. 147. STEVENS, J., filed an opinion concurring in
part and dissenting in part,
post, p. 150.
Steven R. Kuney argued the cause for petitioners. With him on
the briefs were John G. Kester, David H. Flint, Alexander
J.
Simmons, Jr., Henry W Ewalt, and Gerard H. Davidson, Jr.
Deputy Solicitor General Wallace argued the cause for the United
States as amicus curiae urging reversal. With him on the brief were
Acting Solicitor General Dellinger, Assistant Attorney General
Hunger, Edward C. DuMont, and John P. Schnitker.
Michael H. Gottesman argued the cause for
respondents.
With him on the brief were Kenneth
J. Chesebro, David L.
Shapiro, and Michael
J. Warshauer.
*
CHIEF JUSTICE REHNQUIST delivered the opinion of the Court.
We granted certiorari in this case to determine what standard an
appellate court should apply in reviewing a trial
*Briefs of
amici curiae urging reversal were filed for
the Chamber of Commerce of the United States by
Thomas S.
Martin, Stephen A. Bokat, and
Robin S.
Conrad;
for the American Medical Association by
Jack R. Bierig,
Carter G.
Phillips, Kirk B. Johnson, and
Michael L.
Ile; for the Chemical Manufacturers Association by
Bert
Black, David J. Schenck, and
Donald D.
Evans; for Dow Chemical Company by
John E. Muench and
Robert M. Dow, Jr.; for the Pharmaceutical Research and
Manufacturers of America by
Bruce N. Kuhlik; for the
Washington Legal Foundation by
Arvin Maskin, Gerald A. Stein,
Daniel J. Popeo, and
Paul D. Kamenar; and
for Bruce Ames et al. by
Martin S.
Kaufman and
Douglas Foster.
Briefs of
amici curiae urging affirmance were filed for
the Trial Lawyers for Public Justice by
Steven E. Fineman
and
Arthur H. Bryant; for the Association of Trial Lawyers
of America by
Jeffrey Robert White; for Ardith Cavallo by
William A. Beeton, Jr.; and for Peter Orris, M. D., et al.
by
Gerson H. Smoger.
Briefs of
amici curiae were filed for the New England
Journal of Medicine et al. by
Margaret S.
Woodruff
and
Arlin M. Adams; and for the Product Liability Advisory
Council, Inc., et al. by
Mary A. Wells, Jan S.
Amundson, and
Quentin Riegel.
139
court's decision to admit or exclude expert testimony under
Daubert v.
Merrell Dow Pharmaceuticals, Inc.,
509 U. S. 579
(1993). We hold that abuse of discretion is the appropriate
standard. We apply this standard and conclude that the District
Court in this case did not abuse its discretion when it excluded
certain proffered expert testimony.
I
Respondent Robert Joiner began work as an electrician in the
Water & Light Department of Thomasville, Georgia (City), in
1973. This job required him to work with and around the City's
electrical transformers, which used a mineral-oil-based dielectric
fluid as a coolant. Joiner often had to stick his hands and arms
into the fluid to make repairs. The fluid would sometimes splash
onto him, occasionally getting into his eyes and mouth. In 1983 the
City discovered that the fluid in some of the transformers was
contaminated with polychlorinated biphenyls (PCB's). PCB's are
widely considered to be hazardous to human health. Congress, with
limited exceptions, banned the production and sale of PCB's in
1978. See 90 Stat. 2020, 15 U. S. C. § 2605(e)(2)(A).
Joiner was diagnosed with small-cell lung cancer in 1991.
He 1 sued petitioners in Georgia state court the following year.
Petitioner Monsanto manufactured PCB's from 1935 to 1977;
petitioners General Electric and Westinghouse Electric manufactured
transformers and dielectric fluid. In his complaint Joiner linked
his development of cancer to his exposure to PCB's and their
derivatives, polychlorinated dibenzofurans (furans) and
polychlorinated dibenzodioxins (dioxins). Joiner had been a smoker
for approximately eight years, his parents had both been smokers,
and there was a history of lung cancer in his family. He was thus
perhaps already at a heightened risk of developing lung cancer
eventually. The suit alleged that his exposure to PCB's "pro-
IJoiner's wife was also a plaintiff in the suit and is a
respondent here.
For convenience, we refer to respondent in the singular.
140
moted" his cancer; had it not been for his exposure to these
substances, his cancer would not have developed for many years, if
at all.
Petitioners removed the case to federal court. Once there, they
moved for summary judgment. They contended that (1) there was no
evidence that Joiner suffered significant exposure to PCB's,
furans, or dioxins, and (2) there was no admissible scientific
evidence that PCB's promoted Joiner's cancer. Joiner responded that
there were numerous disputed factual issues that required
resolution by a jury. He relied largely on the testimony of expert
witnesses. In depositions, his experts had testified that PCB's
alone can promote cancer and that furans and dioxins can also
promote cancer. They opined that since Joiner had been exposed to
PCB's, furans, and dioxins, such exposure was likely responsible
for Joiner's cancer.
The District Court ruled that there was a genuine issue of
material fact as to whether Joiner had been exposed to PCB's. But
it nevertheless granted summary judgment for petitioners because
(1) there was no genuine issue as to whether Joiner had been
exposed to furans and dioxins, and (2) the testimony of Joiner's
experts had failed to show that there was a link between exposure
to PCB's and small-cell lung cancer. The court believed that the
testimony of respondent's experts to the contrary did not rise
above "subjective belief or unsupported speculation." 864 F. Supp.
1310, 1326 (ND Ga. 1994). Their testimony was therefore
inadmissible.
The Court of Appeals for the Eleventh Circuit reversed.
78 F.3d
524 (1996). It held that "[b]ecause the Federal Rules of
Evidence governing expert testimony display a preference for
admissibility, we apply a particularly stringent standard of review
to the trial judge's exclusion of expert testimony."
Id., at
529. Applying that standard, the Court of Appeals held that the
District Court had erred in excluding the testimony of Joiner's
expert witnesses. The
141
District Court had made two fundamental errors. First, it
excluded the experts' testimony because it "drew different
conclusions from the research than did each of the experts." The
Court of Appeals opined that a district court should limit its role
to determining the "legal reliability of proffered expert
testimony, leaving the jury to decide the correctness of competing
expert opinions."
Id., at 533. Second, the District Court
had held that there was no genuine issue of material fact as to
whether Joiner had been exposed to furans and dioxins. This was
also incorrect, said the Court of Appeals, because testimony in the
record supported the proposition that there had been such
exposure.
We granted petitioners' petition for a writ of certiorari, 520
U. S. 1114 (1997), and we now reverse.
II
Petitioners challenge the standard applied by the Court of
Appeals in reviewing the District Court's decision to exclude
respondent's experts' proffered testimony. They argue that that
court should have applied traditional "abuse of discretion" review.
Respondent agrees that abuse of discretion is the correct standard
of review. He contends, however, that the Court of Appeals applied
an abuse-of-discretion standard in this case. As he reads it, the
phrase "particularly stringent" announced no new standard of
review. I t was simply an acknowledgment that an appellate court
can and will devote more resources to analyzing district court
decisions that are dispositive of the entire litigation. All
evidentiary decisions are reviewed under an abuse-of-discretion
standard. He argues, however, that it is perfectly reasonable for
appellate courts to give particular attention to those decisions
that are outcome determinative.
We have held that abuse of discretion is the proper standard of
review of a district court's evidentiary rulings.
Old Chief
v.
United States, 519 U. S. 172, 174, n. 1
(1997);
United States v.
Abel, 469 U. S. 45, 54 (1984).
Indeed, our cases on
142
the subject go back as far as
Spring Co. v.
Edgar,
99 U. S. 645, 658
(1879), where we said that "[c]ases arise where it is very much a
matter of discretion with the court whether to receive or exclude
the evidence; but the appellate court will not reverse in such a
case, unless the ruling is manifestly erroneous." The Court of
Appeals suggested that
Daubert somehow altered this general
rule in the context of a district court's decision to exclude
scientific evidence. But
Daubert did not address the
standard of appellate review for evidentiary rulings at all. It did
hold that the "austere"
Frye standard of "general
acceptance" had not been carried over into the Federal Rules of
Evidence. But the opinion also said:
"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. 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." 509 U. S., at 589 (footnote omitted).
Thus, while the Federal Rules of Evidence allow district courts
to admit a somewhat broader range of scientific testimony than
would have been admissible under
Frye, they leave in place
the "gatekeeper" role of the trial judge in screening such
evidence. A court of appeals applying "abuse-of-discretion" review
to such rulings may not categorically distinguish between rulings
allowing expert testimony and rulings disallowing it. Compare
Beech Aircraft Corp. v.
Rainey, 488 U. S. 153, 172 (1988)
(applying abuse-ofdiscretion review to a lower court's decision to
exclude evidence), with
United States v.
Abel, supra,
at 54 (applying abuse-of-discretion review to a lower court's
decision to admit evidence). We likewise reject respondent's
argument that because the granting of summary judgment in this
case
143
was "outcome determinative," it should have been subjected to a
more searching standard of review. On a motion for summary
judgment, disputed issues of fact are resolved against the moving
party-here, petitioners. But the question of admissibility of
expert testimony is not such an issue of fact, and is reviewable
under the abuse-of-discretion standard.
We hold that the Court of Appeals erred in its review of the
exclusion of Joiner's experts' testimony. In applying an overly
"stringent" review to that ruling, it failed to give the trial
court the deference that is the hallmark of abuse-ofdiscretion
review. See,
e. g., Koon v.
United
States, 518 U. S.
81, 98-99 (1996).
III
We believe that a proper application of the correct standard of
review here indicates that the District Court did not abuse its
discretion. Joiner's theory of liability was that his exposure to
PCB's and their derivatives "promoted" his development of
small-cell lung cancer. In support of that theory he proffered the
deposition testimony of expert witnesses. Dr. Arnold Schecter
testified that he believed it "more likely than not that Mr.
Joiner's lung cancer was causally linked to cigarette smoking and
PCB exposure." App. 107. Dr. Daniel Teitelbaum testified that
Joiner's "lung cancer was caused by or contributed to in a
significant degree by the materials with which he worked."
Id., at 140.
Petitioners contended that the statements of Joiner's experts
regarding causation were nothing more than speculation. Petitioners
criticized the testimony of the experts in that it was "not
supported by epidemiological studies ... [and was] based
exclusively on isolated studies of laboratory animals." 3 Record,
Doc. No. 46 (Defendants' Joint Memorandum in Support of Summary
Judgment 3). Joiner responded by claiming that his experts had
identified "relevant animal studies which support their opinions."
4 Record, Doc. No. 53 (Plaintiffs' Brief in Opposition to
Defendants'
144
Motion for Summary Judgment 47). He also directed the court's
attention to four epidemiological studies 2 on which his experts
had relied.
The District Court agreed with petitioners that the animal
studies on which respondent's experts relied did not support his
contention that exposure to PCB's had contributed to his cancer.
The studies involved infant mice that had developed cancer after
being exposed to PCB's. The infant mice in the studies had had
massive doses of PCB's injected directly into their peritoneums 3
or stomachs. Joiner was an adult human being whose alleged exposure
to PCB's was far less than the exposure in the animal studies. The
PCB's were injected into the mice in a highly concentrated form.
The fluid with which Joiner had come into contact generally had a
much smaller PCB concentration of between O-to-500 parts per
million. The cancer that these mice developed was alveologenic
adenomas; Joiner had developed small-cell carcinomas. No study
demonstrated that adult mice developed cancer after being exposed
to PCB's. One of the experts admitted that no study had
demonstrated that PCB's lead to cancer in any other species.
Respondent failed to reply to this criticism. Rather than
explaining how and why the experts could have extrapolated their
opinions from these seemingly far-removed animal studies,
respondent chose "to proceed as if the only issue [was] whether
animal studies can ever be a proper foundation for an expert's
opinion." 864 F. Supp., at 1324. Of course, whether animal studies
can ever be a proper foundation for an expert's opinion was not the
issue. The issue was whether
these experts' opinions were
sufficiently supported by the animal studies on which they
purported to rely. The studies were so dissimilar to the facts
presented in this liti-
2 Epidemiological studies examine the pattern of disease in
human populations.
3 The peritoneum is the lining of the abdominal cavity.
145
gation that it was not an abuse of discretion for the District
Court to have rejected the experts' reliance on them.
The District Court also concluded that the four epidemiological
studies on which respondent relied were not a sufficient basis for
the experts' opinions. The first such study involved workers at an
Italian capacitor 4 plant who had been exposed to PCB's. Bertazzi,
Riboldi, Pesatori, Radice, & Zocchetti, Cancer Mortality of
Capacitor Manufacturing Workers, 11 American Journal of Industrial
Medicine 165 (1987). The authors noted that lung cancer deaths
among ex-employees at the plant were higher than might have been
expected, but concluded that "there were apparently no grounds for
associating lung cancer deaths (although increased above
expectations) and exposure in the plant."
Id., at 172. Given
that Bertazzi et aL were unwilling to say that PCB exposure had
caused cancer among the workers they examined, their study did not
support the experts' conclusion that Joiner's exposure to PCB's
caused his cancer.
The second study followed employees who had worked at Monsanto's
PCB production plant. J. Zack & D. Musch, Mortality of PCB
Workers at the Monsanto Plant in Sauget, Illinois (Dec. 14, 1979)
(unpublished report), 3 Record, Doc. No. 11. The authors of this
study found that the incidence of lung cancer deaths among these
workers was somewhat higher than would ordinarily be expected. The
increase, however, was not statistically significant and the
authors of the study did not suggest a link between the increase in
lung cancer deaths and the exposure to PCB's.
The third and fourth studies were likewise of no help.
The third involved workers at a Norwegian cable manufacturing
company who had been exposed to mineral oiL Ronneberg, Andersen,
& Skyberg, Mortality and Incidence of Cancer Among Oil Exposed
Workers in a Norwegian Cable Manufacturing Company, 45 British
Journal of Indus-
4 A capacitor is an electrical component that stores an electric
charge.
146
trial Medicine 595 (1988). A statistically significant increase
in lung cancer deaths had been observed in these workers. The
study, however, (1) made no mention of PCB's and (2) was expressly
limited to the type of mineral oil involved in that study, and thus
did not support these experts' opinions. The fourth and final study
involved a PCB-exposed group in Japan that had seen a statistically
significant increase in lung cancer deaths. Kuratsune, Nakamura,
Ikeda, & Hirohata, Analysis of Deaths Seen Among Patients with
Yusho-A Preliminary Report, 16 Chemosphere, Nos. 8/9, p. 2085
(1987). The subjects of this study, however, had been exposed to
numerous potential carcinogens, including toxic rice oil that they
had ingested.
Respondent points to
Daubert's language that the "focus,
of course, must be solely on principles and methodology, not on the
conclusions that they generate." 509 U. S., at 595. He claims that
because the District Court's disagreement was with the conclusion
that the experts drew from the studies, the District Court
committed legal error and was properly reversed by the Court of
Appeals. But conclusions and methodology are not entirely distinct
from one another. Trained experts commonly extrapolate from
existing data. But nothing in either
Daubert or the Federal
Rules of Evidence requires a district court to admit opinion
evidence that is connected to existing data only by the
ipse
dixit of the expert. A court may conclude that there is simply
too great an analytical gap between the data and the opinion
proffered. See
Turpin v.
Merrell Dow Pharmaceuticals,
Inc., 959 F.2d
1349, 1360 (CA6), cert. denied, 506 U. S. 826 (1992). That is
what the District Court did here, and we hold that it did not abuse
its discretion in so doing.
We hold, therefore, that abuse of discretion is the proper
standard by which to review a district court's decision to admit or
exclude scientific evidence. We further hold that, because it was
within the District Court's discretion to conclude that the studies
upon which the experts relied were not
147
sufficient, whether individually or in combination, to support
their conclusions that Joiner's exposure to PCB's contributed to
his cancer, the District Court did not abuse its discretion in
excluding their testimony. These conclusions, however, do not
dispose of this entire case.
Respondent's original contention was that his exposure to PCB's,
furans, and dioxins contributed to his cancer. The District Court
ruled that there was a genuine issue of material fact as to whether
Joiner had been exposed to PCB's, but concluded that there was no
genuine issue as to whether he had been exposed to furans and
dioxins. The District Court accordingly never explicitly considered
if there was admissible evidence on the question whether Joiner's
alleged exposure to furans and dioxins contributed to his cancer.
The Court of Appeals reversed the District Court's conclusion that
there had been no exposure to furans and dioxins. Petitioners did
not challenge this determination in their petition to this Court.
Whether Joiner was exposed to furans and dioxins, and whether if
there was such exposure, the opinions of Joiner's experts would
then be admissible, remain open questions. We accordingly reverse
the judgment of the Court of Appeals and remand this case for
proceedings consistent with this opinion.
It is so ordered.
JUSTICE BREYER, concurring.
The Court's opinion, which I join, emphasizes
Daubert's
statement that a trial judge, acting as "gatekeeper," must "'ensure
that any and all scientific testimony or evidence admitted is not
only relevant, but reliable.'"
Ante, at 142 (quoting
Daubert v.
Merrell Dow Pharmaceuticals, Inc., 509 U.
S. 579, 589 (1993)). This requirement will sometimes ask judges to
make subtle and sophisticated determinations about scientific
methodology and its relation to the conclusions an expert witness
seeks to offer-particularly when a case arises in an area where the
science itself is tentative or
148
uncertain, or where testimony about general risk levels in human
beings or animals is offered to prove individual causation. Yet, as
amici have pointed out, judges are not scientists and do not
have the scientific training that can facilitate the making of such
decisions. See,
e. g., Brief for Trial Lawyers for
Public Justice as
Amicus Curiae 15; Brief for New England
Journal of Medicine et al. as
Amici Curiae 2 ("Judges ...
are generally not trained scientists").
Of course, neither the difficulty of the task nor any
comparative lack of expertise can excuse the judge from exercising
the "gatekeeper" duties that the Federal Rules of Evidence
impose-determining, for example, whether particular expert
testimony is reliable and "will assist the trier of fact," Fed.
Rule Evid. 702, or whether the "probative value" of testimony is
substantially outweighed by risks of prejudice, confusion or waste
of time, Fed. Rule Evid. 403. To the contrary, when law and science
intersect, those duties often must be exercised with special
care.
Today's toxic tort case provides an example. The plaintiff in
today's case says that a chemical substance caused, or promoted,
his lung cancer. His concern, and that of others, about the causes
of cancer is understandable, for cancer kills over one in five
Americans. See U. S. Dept. of Health and Human Services, National
Center for Health Statistics, Health, United States 1996-97 and
Injury Chartbook 117 (1997) (23.3% of all deaths in 1995).
Moreover, scientific evidence implicates some chemicals as
potential causes of some cancers. See,
e. g., U. S.
Dept. of Health and Human Services, Public Health Service, National
Toxicology Program, 1 Seventh Annual Report on Carcinogens, pp.
v-vi (1994). Yet modern life, including good health as well as
economic well-being, depends upon the use of artificial or
manufactured substances, such as chemicals. And it may, therefore,
prove particularly important to see that judges fulfill their
Daubert gatekeeping function, so that they help assure that
the powerful engine of tort liability, which can generate
149
strong financial incentives to reduce, or to eliminate,
production, points toward the right substances and does not destroy
the wrong ones. It is, thus, essential in this sciencerelated area
that the courts administer the Federal Rules of Evidence in order
to achieve the "end[s]" that the Rules themselves set forth, not
only so that proceedings may be "justly determined," but also so
"that the truth may be ascertained." Fed. Rule Evid. 102.
I therefore want specially to note that, as cases presenting
significant science-related issues have increased in number, see
Judicial Conference of the United States, Report of the Federal
Courts Study Committee 97 (Apr. 2, 1990) ("Economic, statistical,
technological, and natural and social scientific data are becoming
increasingly important in both routine and complex litigation"),
judges have increasingly found in the Rules of Evidence and Civil
Procedure ways to help them overcome the inherent difficulty of
making determinations about complicated scientific, or otherwise
technical, evidence. Among these techniques are an increased use of
Rule 16's pretrial conference authority to narrow the scientific
issues in dispute, pretrial hearings where potential experts are
subject to examination by the court, and the appointment of special
masters and specially trained law clerks. See J. Cecil & T.
Willging, Court-Appointed Experts: Defining the Role of Experts
Appointed Under Federal Rule of Evidence 706, pp. 83-88 (1993); J.
Weinstein, Individual Justice in Mass Tort Litigation 107-110
(1995); cf. Kaysen, In Memoriam: Charles E. Wyzanski, Jr., 100
Harv. L. Rev. 713, 713-715 (1987) (discussing a judge's use of an
economist as a law clerk in
United States v.
United Shoe
Machinery Corp., 110 F. Supp. 295 (Mass. 1953), aff'd,
347 U. S. 521
(1954)).
In the present case, the New England Journal of Medicine has
filed an
amici brief "in support of neither petitioners nor
respondents" in which the Journal writes:
"[A] judge could better fulfill this gatekeeper function if he
or she had help from scientists. Judges should be
150
Opinion of STEVENS, J.
strongly encouraged to make greater use of their inherent
authority ... to appoint experts .... Reputable experts could be
recommended to courts by established scientific organizations, such
as the National Academy of Sciences or the American Association for
the Advancement of Science." Brief, supra, at 18-19.
Cf. Fed. Rule Evid. 706 (court may "on its own motion or on the
motion of any party" appoint an expert to serve on behalf of the
court, and this expert may be selected as "agreed upon by the
parties" or chosen by the court); see also Weinstein,
supra,
at 116 (a court should sometimes "go beyond the experts proffered
by the parties" and "utilize its powers to appoint independent
experts under Rule 706 of the Federal Rules of Evidence"). Given
this kind of offer of cooperative effort, from the scientific to
the legal community, and given the various Rules-authorized methods
for facilitating the courts' task, it seems to me that
Daubert's gatekeeping requirement will not prove
inordinately difficult to implement, and that it will help secure
the basic objectives of the Federal Rules of Evidence, which are,
to repeat, the ascertainment of truth and the just determination of
proceedings. Fed. Rule Evid. 102.
JUSTICE STEVENS, concurring in part and dissenting in part.
The question that we granted certiorari to decide is whether the
Court of Appeals applied the correct standard of review. That
question is fully answered in Parts I and II of the Court's
opinion. Part III answers the quite different question whether the
District Court properly held that the testimony of plaintiff's
expert witnesses was inadmissible. Because I am not sure that the
parties have adequately briefed that question, or that the Court
has adequately explained why the Court of Appeals' disposition was
erroneous, I do not join Part III. Moreover, because a proper
answer to that question requires a study of the record that can
be
151
performed more efficiently by the Court of Appeals than by the
nine Members of this Court, I would remand the case to that court
for application of the proper standard of review.
One aspect of the record will illustrate my concern. As the
Court of Appeals pointed out, Joiner's experts relied on "the
studies of at least thirteen different researchers, and referred to
several reports of the World Health Organization that address the
question of whether PCBs cause cancer."
78 F.3d
524, 533 (CAll 1996). Only one of those studies is in the
record, and only six of them were discussed in the District Court
opinion. Whether a fair appraisal of either the methodology or the
conclusions of Joiner's experts can be made on the basis of such an
incomplete record is a question that I do not feel prepared to
answer.
It does seem clear, however, that the Court has not adequately
explained why its holding is consistent with Federal Rule of
Evidence 702,1 as interpreted in
Daubert v.
Merrell Dow
Pharmaceuticals, Inc., 509 U. S. 579 (1993).2 In
general, scientific testimony that is both relevant and reliable
must be admitted and testimony that is irrelevant or unreliable
must be excluded.
Id., at 597. In this case, the District
Court relied on both grounds for exclusion.
The relevance ruling was straightforward. The District Court
correctly reasoned that an expert opinion that expo-
1 Rule 702 states: "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."
2 The specific question on which the Court granted certiorari in
Daubert was whether the rule of
Frye v.
United
States, 54 App. D. C. 46,
293 F.1d
13 (1923), remained valid after the enactment of the Federal
Rules of Evidence, but the Court went beyond that issue and set
forth alternative requirements for admissibility in place of the
Frye test. Even though the
Daubert test was announced
in dicta, see 509 U. S., at 598-601 (REHNQUIST, C. J., concurring
in part and dissenting in part), we should not simply ignore its
analysis in reviewing the District Court's rulings.
152
Opinion of STEVENS, J.
sure to PCB's, "furans" and "dioxins" together may cause lung
cancer would be irrelevant unless the plaintiff had been exposed to
those substances. Having already found that there was no evidence
of exposure to furans and dioxins, 864 F. Supp. 1310, 1318-1319 (ND
Ga. 1994), it necessarily followed that this expert opinion
testimony was inadmissible. Correctly applying
Daubert, the
District Court explained that the experts' testimony "manifestly
does not fit the facts of this case, and is therefore
inadmissible." 864 F. Supp., at 1322. Of course, if the evidence
raised a genuine issue of fact on the question of Joiner's exposure
to furans and dioxins-as the Court of Appeals held that it did-then
this basis for the ruling on admissibility was erroneous, but not
because the District Judge either abused her discretion or
misapplied the law.3
The reliability ruling was more complex and arguably is not
faithful to the statement in
Daubert that "[t]he focus, of
course, must be solely on principles and methodology, not on the
conclusions that they generate." 509 U. S., at 595. Joiner's
experts used a "weight of the evidence" methodology to assess
whether Joiner's exposure to transformer fluids promoted his lung
cancer.4 They did not suggest that any
3 Petitioners do not challenge the Court of Appeals'
straightforward review of the District Court's summary judgment
ruling on exposure to furans and dioxins. As today's opinion
indicates,
ante, at 147, it remains an open question on
remand whether the District Court should admit expert testimony
that PCB's, furans, and dioxins
together promoted Joiner's
cancer.
4 Dr. Daniel Teitelbaum elaborated on that approach in his
deposition testimony: "[A]s a toxicologist when I look at a study,
I am going to require that that study meet the general criteria for
methodology and statistical analysis, but that when all of that
data is collected and you ask me as a patient, 'Doctor, have I got
a risk of getting cancer from this?' That those studies don't
answer the question, that I have to put them all together in my
mind and look at them in relation to everything I know about the
substance and everything I know about the exposure and come to a
conclusion. I think when I say, 'To a reasonable medical
probability as a medical toxicologist, this substance was a
contributing cause,' ... to his cancer,
153
one study provided adequate support for their conclusions, but
instead relied on all the studies taken together (along with their
interviews of Joiner and their review of his medical records). The
District Court, however, examined the studies one by one and
concluded that none was sufficient to show a link between PCB's and
lung cancer. 864 F. Supp., at 1324-1326. The focus of the opinion
was on the separate studies and the conclusions of the experts, not
on the experts'methodology.
Id., at 1322 ("Defendants ...
persuade the court that Plaintiffs' expert testimony would not be
admissible ... by attacking the conclusions that Plaintiffs'
experts draw from the studies they cite").
Unlike the District Court, the Court of Appeals expressly
decided that a "weight of the evidence" methodology was
scientifically acceptable.5 To this extent, the Court of Appeals'
opinion is persuasive. It is not intrinsically "unscientific" for
experienced professionals to arrive at a conclusion by weighing all
available scientific evidence-this is not the sort of "junk
science" with which
Daubert was concerned.6 After all, as
Joiner points out, the Environmental Protection Agency (EPA) uses
the same methodology to assess risks, albeit using a somewhat
different threshold than that required in a trial. Brief for
Respondents 40-41 (quoting
that that is a valid conclusion based on the totality of the
evidence presented to me. And I think that that is an appropriate
thing for a toxicologist to do, and it has been the basis of
diagnosis for several hundred years, anyway." Supp. App. to Brief
for Respondents 19.
5 The court explained: "Opinions of any kind are derived from
individual pieces of evidence, each of which by itself might not be
conclusive, but when viewed in their entirety are the building
blocks of a perfectly reasonable conclusion, one reliable enough to
be submitted to a jury along with the tests and criticisms
cross-examination and contrary evidence would supply."
78 F.3d
524, 532 (CAll 1996).
6 An example of "junk science" that should be excluded under
Daubert as too unreliable would be the testimony of a
phrenologist who would purport to prove a defendant's future
dangerousness based on the contours of the defendant's skull.
154
Opinion of STEVENS, J.
EPA, Guidelines for Carcinogen Risk Assessment, 51 Fed. Reg.
33992, 33996 (1986)). Petitioners' own experts used the same
scientific approach as well. 7 And using this methodology, it would
seem that an expert could reasonably have concluded that the study
of workers at an Italian capacitor plant, coupled with data from
Monsanto's study and other studies, raises an inference that PCB's
promote lung cancer.8
The Court of Appeals' discussion of admissibility is faithful to
the dictum in
Daubert that the reliability inquiry must
focus on methodology, not conclusions. Thus, even though I fully
agree with both the District Court's and this Court's explanation
of why each of the studies on which the experts relied was by
itself unpersuasive, a critical question remains unanswered: When
qualified experts have reached relevant conclusions on the basis of
an acceptable methodology, why are their opinions inadmissible?
Daubert quite clearly forbids trial judges to assess the
validity or strength of an expert's scientific conclusions, which
is a matter for the jury.9 Because I am persuaded
7 See,
e. g., Deposition of Dr. William Charles
Bailey, Supp. App. to Brief for Respondents 56 ("I've just reviewed
a lot of literature and come to some conclusions ... ").
8 The Italian capacitor plant study found that workers exposed
to PCB's had a higher-than-expected rate of lung cancer death,
though "'the numbers were small [and] the value of the risk
estimate was not statistically significant.''' 864 F. Supp. 1310,
1324 (ND Ga. 1994). The Monsanto study also found a correlation
between PCB exposure and lung cancer death, but the results were
not statistically significant.
Id., at 1325. Moreover, it
should be noted that under Georgia law, which applies in this
diversity suit, Joiner need only show that his exposure to PCB's
'''promoted' " his lung cancer, not that it was the sole cause of
his cancer. Brief for Respondents 7, n. 16 (quoting Brief for
Appellants in No. 94-9131 (CAll), pp. 7-10).
9 The Court stated in
Daubert: "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 ....
Additionally, in the event the trial court concludes that the
scintilla of evidence presented supporting a position is
insufficient to
155
that the difference between methodology and conclusions is just
as categorical as the distinction between means and ends, I do not
think the statement that "conclusions and methodology are not
entirely distinct from one another,"
ante, at 146, either is
accurate or helps us answer the difficult admissibility question
presented by this record.
In any event, it bears emphasis that the Court has not held that
it would have been an abuse of discretion to admit the expert
testimony. The very point of today's holding is that the
abuse-of-discretion standard of review applies whether the district
judge has excluded or admitted evidence.
Ante, at 142. And
nothing in either
Daubert or the Federal Rules of Evidence
requires a district judge to reject an expert's conclusions and
keep them from the jury when they fit the facts of the case and are
based on reliable scientific methodology.
Accordingly, while I join Parts I and II of the Court's opinion,
I do not concur in the judgment or in Part III of its opinion.
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 .... 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." 509 U. S.,
at 596.
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