Kumho and How We Know

Abstract

JOSEPH SANDERS [*] I INTRODUCTION In the summer of 1999, the United States Supreme Court issued the last in a trilogy of 1990s cases dealing with the question of the admissibility of expert testimony in federal courts. [1] In Kumho Tire Co. v. Carmichael, [2] the Court was asked to decide if the judicial gatekeeping role it set forth in the first of these three cases, Daubert v. Merrell Dow Pharmaceuticals, [3] applied only to "scientific" knowledge or to all expert testimony. The court concluded that all expert testimony must be both relevant and reliable before it can be admitted, but that the specific factors set forth in Daubert to judge the reliability of scientific evidence may be supplemented and perhaps replaced by other factors when expert testimony is based on "technical" or "other specialized" knowledge. [4] The opinion explicitly recognized that not all expert testimony can be judged by a single standard because not all experts know things in exactly the same way. [5] This point had been colorfully made five years earlier in the Sixth Circuit's opinion in Berry v. City of Detroit. [6] In Berry, while wrestling with the admissibility of the expert testimony of a "sociologist cum sheriff" [7] as to whether the disciplinary practices of the Detroit police department demonstrated a policy of deliberate indifference to the rights of the citizenry, thus giving rise to municipal liability under 42 U.S.C. [sections] 1983, the Sixth Circuit made the following comparison between scientific and nonscientific expert testimony: The distinction between scientific and non-scientific expert testimony is a critical one. By way of illustration, if one wanted to explain to a jury how a bumblebee is able to fly, an aeronautical engineer might be a helpful witness. Since flight principles have some universality, the expert could apply general principles to the case of the bumblebee. Conceivably, even if he had never seen a bumblebee, he still would be qualified to testify, as long as he was familiar with its component parts. On the other hand, if one wanted to prove that bumblebees always take off into the wind, a beekeeper with no scientific training at all would be an acceptable expert witness if a proper foundation were laid for his conclusions. The foundation would not relate to his formal training, but to his firsthand observations. In other words, the beekeeper does not know any more about flight principles than the jurors, but he has seen a lot more bumblebees than they have. [8] How do aeronautical engineers and beekeepers know what they know? How does their knowledge differ and how is it the same? The insight of the Berry opinion is that a satisfactory answer to the legal question of admissibility is in part contingent upon our understanding of the nature of expert knowledge. But this alone is not enough. Admissibility standards are also influenced by the organization of the legal system itself. In this article, I attempt to shed some light on different ways experts (and non-experts) know things and then to offer some thoughts on how this should influence the legal assessment of the admissibility of expert testimony. [9] In Part II, I review the legal developments leading up to Kumho. I give special emphasis to the alternative approaches to admissibility reflected in the Frye [10] and Daubert [11] tests and to the Kumho decision to sweep non-scientific evidence under the Daubert umbrella. [12] Part III addresses two questions: What is the law's implicit epistemology with respect to scientific knowledge, and how does scientific knowledge differ from other forms of knowing? I argue that while there may be differences between intellectual fields along such dimensions as a reliance on individual "experience" as a basis of judgment, and the ability of fields to isolate themselves from political, economic, and social pressures, the differences are often as great within disciplines as between them. …