In 1993, the Supreme Court’s opinion in Daubert v. Merrell Dow Pharmaceuticals1 ushered in a new era with regard to the admissibility of expert testimony. As expert testimony has become increasingly essential in a wide variety of litigated cases, the Daubert opinion has had an enormous impact. If plaintiffs’ expert proof is excluded on a crucial issue, plaintiffs cannot win and usually cannot even get their case to a jury. This discussion begins with a brief overview of the Supreme Court’s three opinions on expert testimony—often called the Daubert trilogy2—and their impact. It then examines a fourth Supreme Court case that relates to expert testimony, before turning to a variety of issues that judges are called upon to resolve, particularly when the proffered expert testimony hinges on scientific knowledge.
In the seminal Daubert case, the Court granted certiorari to decide whether the so-called Frye (or “general acceptance”) test,3 which some federal circuits (and virtually all state courts) used in determining the admissibility of scientific evidence, had been superseded by the enactment of the Federal Rules of Evidence in 1973. The Court held unanimously that the Frye test had not survived. Six justices joined Justice Blackmun in setting forth a new test for admissibility after concluding that “Rule 702…clearly contemplates some degree of regulation of the subjects and theories about which an expert may testify.”4 While the two other members of the Court agreed with this conclusion about the role of Rule 702, they thought that the task of enunciating a new rule for the admissibility of expert proof should be left to another day.5
The majority opinion in Daubert sets forth a number of major themes that run throughout the trilogy. First, it recognized the trial judge as the “gatekeeper” who must screen proffered expert testimony.6 Second, the objective of the screening is to ensure that expert testimony, in order to be admissible, must be “not only relevant, but reliable.”7 Although there was nothing particularly novel about the Supreme Court finding that a trial judge has the power to make an admissibility determination—Federal Rules of Evidence 104(a) and 702 pointed to such a conclusion—and federal trial judges had excluded expert testimony long before
1. 509 U.S. 579 (1993).
2. The other two cases are Gen. Elec. Co. v. Joiner, 522 U.S. 136 (1997) and Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999). The disputed issue in all three cases was causation.
3. Frye v. United States, 293 F. 1013 (D.C. Cir. 1923).
4. Daubert, 509 U.S. at 589.
5. Id. at 601.
6. Id. at 589.