The Epistemological Trend in the Evolution of the Law of Expert Testimony: A Scrutiny at Once Broader, Narrower, and Deeper

This article is a contribution to a symposium occasioned by Georgia’s adoption of an evidence code modeled after the Federal Rules of Evidence. The purpose of the article is to trace the evolution of the law governing the admissibility of expert testimony. Prior to the Supreme Court’s 1993 decision in Daubert, most jurisdictions followed some variation of the Frye general acceptance test. There are three noteworthy aspects of the state of the law prior to Daubert. First, many, if not most, Frye jurisdictions limited the reach of the test to instrumental, purportedly scientific evidence. These jurisdictions tended to exempt both soft science such as psychology and non-scientific expertise from scrutiny. Secondly, in some instances courts in Frye jurisdictions took a global approach to evaluating the admissibility of expert testimony. Rather than examining the specific theory or technique the expert relied on, the courts asked whether the general discipline or field was recognized and accepted. Thirdly, since the test was general acceptance, the courts accepted at face value knowledge claims by practitioners of the discipline; if the clear majority of the members of the field had embraced the scientific theory or technique, the courts did not probe beyond the discipline’s ipse dixit. The Daubert trilogy has changed the law governing the admissibility of expert testimony in each of these respects. To begin with, Daubert adopted a broad definition of science, which the lower courts quickly realized applied to soft as well as hard science. In Kumho, the Court made it clear that the reliability test announced in Daubert applies across the board to all species of expert testimony. Next, trilogy establishes that global analysis is no longer acceptable; rather, the trial judge’s responsibility is to evaluate the reliability of the specific theory or technique that the expert proposes relying on. All three cases, Daubert, Joiner, and Kumho subjected the proffered expert testimony to highly particularized scrutiny. Finally, while Daubert rejected the general acceptance and implicitly announced that the ipse dixit claims by the field are unacceptable, Joiner and Kumho explicitly ruled that ipse dixit claims by individual experts are equally unsatisfactory. As a result of these changes, the law of expert testimony is evolving toward an epistemological analysis of proffered expert evidence – a scrutiny that is at once broader, narrower, and deeper than the pre-Daubert mode of analysis. The Court has made it clear that the trial judge must test the expert’s knowledge claim. The claim is not exempt from scrutiny because it relates to soft science or non-scientific expertise. Nor is the claim exempt because the expert making the claim is a member of a recognized field. The expert must establish that there is a sufficient warrant for the specific knowledge claim that he or she is making. This trend toward an epistemological approach is no accident. In both Daubert and Kumho, the Court began its analysis by construing the word “knowledge” in the text of Federal Rule of Evidence 702. Even more importantly, when the Daubert Court undertook to define “scientific” in Rule 702, the Court focused on science as a methodology or process for validating claims. That focus leads naturally to an epistemological approach. Many of the great epistemologists, including Aristotle, Hume, and Collingwood were serious students of the scientific method precisely because they appreciated that it was a premier technique for validating knowledge claims. If we are interested in accurate judicial outcomes, moving toward a fundamentally epistemological approach is a step in the right direction.