GENERAL ELECTRIC CO. v. JOINER (96-188) 78 F.3d 524, reversed and remanded.
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
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
See United States v. Detroit Timber & Lumber Co., 200 U.S. 321, 337.
SUPREME COURT OF THE UNITED STATES
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
sued in Georgia state court, alleging, inter alia, that his
disease was "promoted" by his workplace exposure to chemical "PCBs" 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
PCBs, 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 PCBs, 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 PCBs 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.
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. 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. 4—5.
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 PCBs 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 PCBs. Nothing in either Daubert or
the Federal Rules of Evidence requires a district court to admit opinion
evidence which is connected to existing data only by the ipse dixit of
the expert. Pp. 6—9.
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. Pp. 9—10.
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. Stevens,
J., filed an opinion concurring in part and dissenting in part.
Opinion of the Court
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,
Washington, D. C. 20543, of any typographical or other formal errors,
in order that corrections may be made before the preliminary print goes
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 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.
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-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 (PCBs). PCBs are widely
considered to be hazardous to human health. Congress, with limited exceptions,
banned the production and sale of PCBs 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 
sued petitioners in Georgia state court the following year. Petitioner
Monsanto manufactured PCBs 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 PCBs 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 PCBs "promoted" 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 PCBs, furans, or dioxins, and
(2) there was no admissible scientific evidence that PCBs 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 PCBs
alone can promote cancer and that furans and dioxins can also promote
cancer. They opined that since Joiner had been exposed to PCBs, 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 PCBs. 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 PCBs 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, 1329 (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 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. _____
(1997), and we now reverse.
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. It was simply an acknowledgement 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. ____, ____ n. 1 (1997) (slip op., at 1—2, n.1), United
States v. Abel, 469 U.S. 45, 54 (1984). Indeed, our cases on the
subject go back as far as Spring Co. v. Edgar, 99 U.S. 645,
658 (1879) where we said that "cases 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 which disallow it. Compare Beech Aircraft Corp v. Rainey,
488 U.S. 153, 172 (1988) (applying abuse of discretion 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 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 of discretion review. See, e.g., Koon
v. United States, 518 U.S. ____, ____ (1996)(slip op., at 14—15).
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 PCBs 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. at 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
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." Joiner responded by claiming that his experts had identified
"relevant animal studies which support their opinions." He
also directed the court’s attention to four epidemiological studies 
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 PCBs had contributed to his cancer. The studies involved
infant mice that had developed cancer after being exposed to PCBs. The
infant mice in the studies had had massive doses of PCBs injected directly
into their peritoneums  or stomachs. Joiner was an
adult human being whose alleged exposure to PCBs was far less than the
exposure in the animal studies. The PCBs 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 0—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 PCBs. One of
the experts admitted that no study had demonstrated that PCBs 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." Joiner, 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 litigation 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
 plant who had been exposed to PCBs. 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 PCBs caused his cancer.
The second study followed employees who had worked at Monsanto’s PCB
production plant. J. Zack & D. Munsch, Mortality of PCB Workers at
the Monsanto Plant in Sauget, Illinois (Dec. 14, 1979)(unpublished report),
3 Rec., 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 PCBs.
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 Industrial 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 PCBs 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, 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 which 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 (CA 6), 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 sufficient, whether individually or in combination, to support
their conclusions that Joiner’s exposure to PCBs 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 PCBs, 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 PCBs, 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.
Joiner’s wife was also a plaintiff in the
suit and is a respondent here. For convenience, we refer to respondent
in the singular.
Epidemiological studies examine the pattern
of disease in human populations.
The peritoneum is the lining of the abdominal
A capacitor is an electrical component that
stores an electric charge.
Breyer, J., concurring
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 5 (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 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 The 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 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 strong
financial incentives to reduce, or to eliminate, production, points towards
the right substances and does not destroy the wrong ones. It is, thus,
essential in this science-related 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
but also so "that the truth may be ascertained." Fed. Rule
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 (D Mass 1953), aff’d, 347 U.S.
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 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 for The New England Journal of Medicine 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.
Opinion of Stevens, J.
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 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 (CA11 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, 
as interpreted in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509
U.S. 579 (1993).  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 exposure to PCBs, "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. 
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. 
They did not suggest that any 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 PCBs 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
Unlike the District Court, the Court of Appeals expressly decided that
a "weight of the evidence" methodology was scientifically acceptable.
 To this extent, the Court of Appeals’ opinion is
persuasive. It is not intrinsically
"unscientific" for experienced professionals to arrive at a
conclusion by weighing all available scientific evidence– this is not
the sort of
"junk science" with which Daubert was concerned.
 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 EPA, Guidelines for Carcinogen Risk Assessment,
51 Fed. Reg. 33992, 33996 (1986)). Petitioners’ own experts used the
same scientific approach as well.  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
PCBs promote lung cancer. 
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 from assessing
the validity or strength of an expert’s scientific conclusions, which
is a matter for the jury.  Because I am persuaded
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 9, is either 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 5. 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.
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."
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. 1013 (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.
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 10, it remains an open question on remand whether the District
Court should admit expert testimony that PCBs, furans and dioxins together promoted
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, 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.
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 (CA11 1996).
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.
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 .
. . .").
The Italian capacitor plant study found
that workers exposed to PCBs 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
"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 (CA 11), pp. 7—10).
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 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.