The impact of Daubert v. Merrell Dow Pharmaceuticals, Inc., on expert testimony: with applications to securities litigation.

• Author: Mahle, Stephen
• Position: U.S. and Florida law

Daubert began a wide-ranging debate about the rules that govern the admissibility in both state and federal trials.

When the U. S. Supreme Court handed down its opinion in Daubert v. Merrell Dow Pharmaceuticals, Inc., 125 L. Ed. 2d 469 (1993), it began a wide-ranging debate about the rules that govern the admissibility of expert testimony in both state and federal trials. The courts of 19 states have adopted Daubert, and those of 11 states, including Florida, apparently have rejected it.[1] Over 100 articles have been published in response to the decision,[2] and there are several Daubert websites, including one sponsored by Harvard Law School. This vigorous response is not surprising, because Daubert held that the Federal Rules of Evidence had displaced the 50-year-old Frye "generally accepted" standard for the admissibility of scientific testimony in federal trials and then determined a new "standard for admitting expert scientific testimony in a federal trial." Daubert, 125 L. Ed. 2d at 476. Despite substantial disagreement in the legal community about what Daubert really means, this article's perspectives are that the meaning of the Court's scientific dialogue is fairly clear and that even though the scientific principles that the Court articulates are ultimately discussed as scientific and statistical concepts that are somewhat alien to the legal system, the Court's holding has its basis in principles of philosophy and logic that have long informed the law.

The philosophy of science that the Court draws so heavily upon focuses on the nature of scientific investigation and informs virtually all of modern scientific inquiry, from DNA testing (do the blood samples match?), through medicine (does smoking cause lung cancer?), epidemiology (does Bendectin cause birth defects in human embryos?), economics (does spending rise with income?), and finance (did the re]ease of fraudulent information cause the firm's stock to rise?). The philosophy of science provides the framework that practitioners in all of these disciplines use to analyze data to find out whether their theories (smoking causes cancer; the release of fraudulent information caused the stock's price to rise) are correct, and once one understands the philosophical basis of science upon which the Court relies, much of the statistical part of scientific testimony just plain makes sense and that is half, and perhaps more, of understanding the entirety of the expert testimony that is offered in courts today.

This article begins by outlining the Court's holding and discussing the scientific framework that is the basis of the Court's analysis. Included in this discussion of the scientific framework employed by the Court is a discussion of how the fundamental statistical concepts that experts use in their testimony have evolved from the scientific framework that the Court articulates. Most of the article's statistical analysis of existing cases is from disciplines like epidemiology and DNA testing, since those are the areas that have most notably made their way into the legal system. However, the article also draws parallels from the techniques used by epidemiologists and DNA analysts to analogous techniques used in other fields, especially finance and economics. Demonstrating the similarity of the scientific techniques employed in these branches of science supports the article's contention that once one becomes conversant in the scientific techniques used in any one of these disciplines, that knowledge goes a long way toward understanding the scientific techniques used in the others. The article concludes with a discussion of the role of Daubert in Florida courts, which seems to be somewhat more extensive than what some Florida courts believe it to be.

The Daubert Court begins its explanation of the criteria that trial courts should use to screen "purportedly scientific evidence" by parsing Rule 702, focusing on the meanings of "scientific" and "knowledge."[3] An important key to understanding the Court's reliability-based analysis of the admissibility of expert testimony lies in the Court's focus on the requirement that, in order for expert testimony to be admissible, "[t]he subject of an expert's testimony must be `scientific ... knowledge,'" because it is "the requirement that an expert's testimony pertain to `scientific knowledge'" that "establishes a standard of evidentiary reliability" (emphasis added). Daubert, 125 L. Ed. 2d at 480-81. But, "in order to qualify as `scientific knowledge,' an inference or assertion must be derived by the scientific method...." Id. In brief, since only scientific knowledge can be offered as scientific expert testimony, and the Court regards as scientific knowledge only that which is derived by the scientific method, only inferences that are derived by the scientific method can be offered as expert testimony.

The Court repeatedly uses the phrase "the scientific method." This is a term of art with a specific meaning in the scientific community, and the Court's discussion of the scientific method quotes from seminal works on scientific inquiry more than enough to make it clear that the Court is using the term in that manner. Indeed, much of the language relied upon by the Court in its discussion of the scientific method is strikingly similar to the language used in several amicus briefs filed by or on behalf of scientists from industry and academia.[4] The Court stated that:

Ordinarily, a key question to be answered in determining whether a theory or technique is scientific knowledge that will assist the trier of fact will be whether it can be (and has been) tested. "Scientific methodology today is based on generating hypotheses and testing them to see if they can be falsified; indeed, this methodology is what distinguishes science from other fields of human inquiry."[5]

Daubert, 125 L. Ed. 2d at 483 (emphasis added).

The testing of hypotheses that the Court's emphasized language requires is called "hypothesis testing" and as the Court's quotations indicate, hypothesis testing is the essence of the scientific method. It is noteworthy that the Daubert Court required that experts follow this "scientific method" even before it turned to the four factors that commentators and lower courts have fixed upon. This is noteworthy because the scientific method is the cornerstone of the philosophy of science and because testimony that conforms to the scientific method will always satisfy the Court's first two criteria. The four Daubert criteria for evaluating the admissibility of expert testimony are: 1) whether the methods upon which the testimony is based are centered upon a testable hypothesis; 2) the known or potential rate of error associated with the method; 3) whether the method has been subject to peer review; and 4) whether the method is generally accepted in the relevant scientific community.[6] Given the rest of the opinion, it seems appropriate that the first two of the Court's four criteria amount to asking whether the techniques upon which the testimony is based are grounded in the scientific method. It is no less...