DEPARTMENT OF JUSTICE
|TO:||File 137420.XCP0095-97 (THE FORCE)|
Assistant Attorney General
|RE:||Admissibility of Expert Testimony After Daubert|
|DA:||June 8, 1998|
Attorney Work Product
Prepared in Contemplation of Litigation:
The U.S. Supreme Court held in Daubert I that the Federal Rules of Evidence, not Frye, provide the standard for admitting expert scientific testimony in a federal trial. Rule 702 provides:
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.
"If scientific ... knowledge will assist the trier of fact ..." an expert "may testify thereto." Emphasis added at 509 US 590. The adjective "scientific" implies a grounding in the methods and procedures of science, while "knowledge" "connotes a body of known facts or of ideas inferred from such facts or accepted as true on good grounds." Id. citing Webster's Third at 1252 (1986). Scientists do not assert that they know what is immutably "true," but, in order to qualify as "scientific knowledge," "an inference or assertion must be derived by the scientific method." Id. (emphasis added). Thus the requirement that an expert's testimony pertain to "scientific knowledge" establishes a standard or evidentiary reliability, that is trustworthiness. Id. text and fn. 9 (emphasis added)
The trial judge must thus make a preliminary assessment of whether the testimony's underlying reasoning or methodology is scientifically valid (as well as of whether that reasoning methodology properly can be applied to the facts in issue, that is, whether the testimony is relevant). Id. 591. Considerations which bear on this inquiry include
The inquiry, though a "flexible" one, must focus on principles and methodology. Id. at 594-595 (emphasis added).
The trial judge should also be mindful of other applicable Rules. E.g., as
Judge Weinstein explained: "Expert evidence can be both powerful and quite misleading because of the difficulty of evaluating it. Because of this risk, the judge in weighing possible prejudice against probative force under Rule 403... exercises more control over experts than over lay witnesses." Weinstein, 138 F.R.D., at 632.
Evidence based on valid principles may be challenged by cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof, rather than on Frye's "uncompromising" "general acceptance" standard. Also, if the trial judge 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 ... and likewise to grant summary judgment. ... " Id. 596 (citations omitted)
Even limited screening by the judge may, on occasion, prevent the jury from hearing of authentic scientific breakthroughs. This is the price that must be paid for having the Rules function not to seek cosmic understanding, but to resolve particularized legal disputes. Id. 596-597.
Before the US Supreme Court issued its decision in Daubert I, the Ninth Circuit had affirmed the district court's grant of summary judgment in that case "largely because the opinions proffered by plaintiffs' experts run counter to the substantial consensus of the scientific community." 43 F3d 1311, 1314 (9th Cir. 1995) (Daubert II). On remand, Circuit Judge Kozinski undertook "the task of ensuring that an expert's testimony both rests on a reliable foundation and is relevant to the task at hand." Id. 1313. Judge Kozinski considered that the task of federal judges ruling on the admissibility of expert scientific testimony face a far more complex and daunting task post-Daubert:
First, we must determine nothing less than whether the experts' testimony reflects "scientific knowledge," whether their findings are "derived by the scientific method ," and whether their work product amounts to "good science." Second we must ensure that the proposed expert testimony is "relevant to the task at hand, ... i.e., that it logically advances a material aspect of the proposing party's case.
43 F3d 1315. The court opined that this task is still more daunting when the dispute concerns matters "at the very cutting edge of scientific research, where fact meets theory and certainty dissolves into probability." Id. 1316.
Despite its misgivings, the court ably articulated the fundamental task as "to analyze not what the experts say, but their basis for saying it." The court rhetorically asked itself, "How do we figure out whether scientists have derived their findings through the scientific method or whether their testimony is based on scientifically valid principles." Id. 1316. The answer boils down to determining "whether the analysis undergirding the experts' testimony falls within the range of accepted standards governing how scientists construct their research and reach their conclusions." Id. 1317.
The two principal ways a proponent of expert testimony can show that the evidence satisfies this "first prong" of Rule 702 are (1) establishing that an expert's proffered testimony "grows out of pre-litigation research" or (2) that the expert's research has been subjected to peer review. Id. 1318. The criterion of "pre-litigation research" poses the question whether the experts propose to testify about matters "growing naturally and directly out of research they have conducted independent of the litigation, or whether they have developed their opinions expressly for purposes of testifying." Id. 1317. "That an expert testifies based on research he has conducted independent of the litigation provides important, objective proof that the research comports with the dictates of good science" (by contrast with the practice of expert-shopping, which leads to bad science). The court believes that the reliability of such research consists of its being "less likely to have been biased toward a particular conclusion by the promise of remuneration," the fact that to be conducted "in the usual course of business" it "must normally satisfy a variety of standards to attract funding and institutional support," and the fact that usually, only a limited number of scientists are actively conducting research on the subject that is germane to a given case, thus providing a natural constraint on the parties' ability to shop for experts who agree with them. Id. 1317. For these reasons, being based directly on "legitimate, pre-existing research unrelated to the litigation provides the most persuasive basis for concluding that the opinions [an expert] expresses were 'derived by the scientific method."' Id.
If proffered scientific testimony is not based on independent research, another means of showing its basis in scientifically valid principles is by proof that "the research and analysis supporting the proffered conclusions have been subjected to normal scientific scrutiny through peer review and publication." Id. 1318, text n. 6. The court refers, "of course, to publication in a generally-recognized scientific journal that conditions publication on a bona fide process of peer review." The court here cites generally The Journal's Peer Review Process, 321 New Eng. J. Med. 837 (1989). Id. n. 6. That the research is accepted for publication "in a reputable scientific journal after being subjected to the usual rigors of peer review is a significant indication that it is taken seriously by other scientists, i.e., that it meets at least the minimal criteria for good science." If nothing else, peer review and publication "increase the likelihood that substantive flaws in methodology will be detected." Id. 1318, citing Daubert I, 113 CST at 2797.
Showing that preferred testimony grows out of independent, pre-litigation research or has been subjected to peer review constitute a prima facie case as to admissibility under Rule 702. The opposing party could then challenge that showing by "presenting evidence (including expert testimony) that the proposing party's expert employed unsound methodology or failed to assiduously follow an otherwise sound protocol." Where the opposing party thus raises a material dispute as to admissibility, the district court must hold an in limine hearing to consider the conflicting evidence and make findings about the soundness and reliability of the methodology employed by the scientific experts. Id. at n. 10, citing Fed.R.Evid. 104(a) and 706.
If a party cannot show that its expert's testimony is based on pre-litigation research or has been subjected to peer review, the proponent may attempt to satisfy its burden by the testimony of its own experts, who "must explain precisely how they went about reaching their conclusions and point to some objective source -- a learned treatise, the policy statement of a professional association, a published article in a reputable scientific journal or the like -- to show that they have followed the scientific method, as it is practiced by (at least) a recognized minority of scientists in their field. Id. 1319 citing US v. Rincon, 28 F3d 921, 924 (9th Cir. 1994) for the proposition that research must be described "in sufficient detail that the district court [can] determine if the research was scientifically valid." Since the focus is on reliability, the parties are not limited to what is generally accepted; however, the fact that a party's expert used a methodology accepted by only a minority of scientists would be a proper basis for impeachment at trial. Id. n 11.