Scientific Evidence

A third admissibility test eventually emerged from the Frye debates; the new test rejected the Frye standard but demanded proof of reliability. The Supreme Court adopted this approach in 1993, ruling that the Federal Rules of Evidence had displaced the Frye test. The case, Daubert v. Merrell Dow Pharmaceuticals, Inc. , involved the admissibility of expert epidemiological testimony concerning whether Bendectin, an anti-nausea drug, causes birth defects. In place of Frye, the Court substituted a reliability test. The test, in the Court's view, derived from a federal statute, Evidence Rule 702, which uses the terms "scientific" and "knowledge." The Court embraced a classically Newtonian understanding of scientific methodology—the process of formulating a hypothesis and then engaging in experimentation or observation to falsify or validate the hypothesis. "[I]n order to qualify as 'scientific knowledge,' an inference or assertion must be derived by the scientific method. Proposed testimony must be supported by appropriate validation– i.e., 'good grounds,' based on what is known. In short, the requirement that an expert's testimony pertain to 'scientific knowledge' establishes a standard of evidentiary reliability" (p. 590). In performing this "gatekeeping role," the trial court may consider a number of factors. First, the court should determine whether the scientific theory or technique has been tested. Citing scientific authorities, the Court recognized that a hallmark of science is empirical testing. Second, whether a theory or technique had been subjected to peer review and publication is "a relevant, though not dispositive, consideration in assessing. . . scientific validity." The peer review and publication process increase the likelihood that flaws will be revealed. They thus serve as circumstantial evidence that the hypothesis has been validated by sound scientific methodology. Third, a technique's "known or potential rate of error" is a pertinent factor. Fourth, the "existence and maintenance of standards controlling the technique's operation" is another indicia of trustworthiness. Finally, "general acceptance" remains an important consideration. Although the Court rejected "general acceptance" as the sole criterion for admissibility as in the Frye test, it recognized its relevance in assessing the reliability of scientific evidence. Again, this factor can be important circumstantial evidence of the soundness of the research underlying the expert's hypothesis.

Although the Daubert decision was a civil case, it applied to federal criminal trials as well. Its ancestry can be traced to civil litigation concerning toxic torts (asbestos, Agent Orange, and silicone breast implants) in the 1980s. Frye had rarely been applied to civil cases until the 1980s. At this point, the Frye test, which had previously been championed by the criminal defense bar, was adopted by big business in their battle against "junk science." A plank against junk science appeared in the Republican platform in 1988; and President George Bush, by executive order, imposed a modified Frye test on Justice Department lawyers in civil cases. Inconsistently, the same Justice Department was advocating a lower standard, the complete rejection of Frye, in criminal DNA cases (Giannelli, 1993).

Application in the states. Daubert's effect on state jurisdictions depends on several factors. As previously stated, Daubert rests on an interpretation of the Federal Rules of Evidence, a federal statute. As a statutory rather than a constitutional case, Daubert is not binding on the states, which are therefore free to continue to follow Frye. The state courts have that freedom even in the forty jurisdictions with evidence codes modeled after the Federal Rules, some of which still adhere to the Frye test. Although numerous jurisdictions have rejected Frye in favor of the Daubert approach, other courts have retained the Frye test. For example, the Arizona Supreme Court declined to follow Daubert, noting that it was "not bound by the United States Supreme Court's non-constitutional construction of the Federal Rules of Evidence when we construe the Arizona Rules of Evidence" (State v. Bible, 858 P.2d 1152, 1183 (Ariz. 1993), cert. denied, 511 U.S. 1046 (1994)). Indeed, Frye still has adherents in some of the most populous states—California, New York, Pennsylvania, Michigan, and Florida. Courts retaining Frye have found Daubert wanting. The Washington Supreme Court declared: "While Frye may be difficult to apply in some contexts, this is a result of the complexity of the particular science at issue, the extent to which the scientific community has made its view known, and the extent of any dispute in the scientific community. . . . Questions of admissibility of complex, controversial scientific techniques or methods, like those involving DNA evidence, are going to be difficult under either standard" (State v. Copeland, 922 P.2d 1304, 1314 (Wash. 1996)).

Post-Daubert issues. Although the Daubert decision resolved a number of significant issues, like most landmark cases, it left many questions unanswered. One question raised by the Daubert opinion is whether the Supreme Court intended its reliability test to be more permissive than the Frye test. There is some language in the opinion that points in this direction, and a number of courts have embraced this position. The polygraph cases are a good example. In United States v. Posado, 57 F.3d 428, 429 (5th Cir. 1995), the Fifth Circuit stated that "the rationale underlying this circuit's per se rule against admitting polygraph evidence did not survive Daubert." The court did not hold that polygraph evidence was admissible but only that admissibility should be left to the discretion of the trial judge.

There is, however, another view—that Daubert sets forth a different, but not necessarily less stringent, standard. Some language in Daubert supports this position, particularly the Court's emphasis on the "gatekeeper" function of the trial judge. Federal courts examining handwriting and hair analysis have questioned the admissibility of testimony based on these traditional techniques, thereby undercutting the notion that Daubert is a more liberal standard.

Technical evidence. In interpreting Rule 702, the Supreme Court in Daubert dealt only with "scientific" evidence. The epidemiological testimony offered in Daubert was purportedly scientific. Rule 702, however, also includes the terms "technical" and "specialized" knowledge. That alternate phrasing raised two issues: (1) whether Daubert's reliability requirement extended to these other types of nonscientific expert testimony, and (2) if so, whether the factors set forth in Daubert for judging reliability applied in this context. In 1999, the Supreme Court in Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), answered both questions in the affirmative. Kumho involved a civil case—a tire blowout accident, in which the Court upheld the trial court's decision to exclude engineering testimony concerning the cause of the blowout. The Court acknowledged that some of the Daubert factors might prove inappropriate in assessing the reliability of certain types of nonscientific testimony. The Court accorded trial judges discretion to select the factors to employ in evaluating the specific type of nonscientific expertise. Kumho applies to criminal cases as well. Accordingly, the Daubert reliability requirement applies across the board to all expert evidence, for example, handwriting and hair comparisons.