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 thebasis 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.9 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.


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. 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.

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 10, it remains an open question on remand whether the District Court should admit expert testimony that PCBs, 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, 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 (CA11 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.

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 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 to PCBs “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).

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 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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