Cite as: 522 U. S. 136 (1997)
Opinion of Stevens, J.
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 toxicolo-gist 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.
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