By David Michaels

In 1993, the US Supreme Court ruled in Daubert v. Merrell Dow Pharmaceuticals, Inc. that judges must act as “gatekeepers” in the courtroom, determining if the scientific evidence introduced is relevant and reliable. The Daubert decision has had tremedous impact on how science is used (and misused) in courts.

That judges are not scientists, and are likely to have difficulty evaluating complex scientific evidence, was underscored in last week’s argument over whether the EPA should regulate the greenhouse gas carbon dioxide as a pollutant. When Justice Antonin Scalia was corrected on his statement about where in the atmosphere carbon dioxide ends up, he responded:

“Troposphere, whatever. I told you before I’m not a scientist.”

Laughter followed.


Scalia’s remarks inspire Cornelia Dean to pen a commentary (sub required) “When Questions of Science Come to a Courtroom, Truth Has Many Faces” in the New York Times. Dean, an insightful writer who served as the newspaper’s Science Editor from 1997 to 2003, describes the inherent conflict between the ways in which science and the law evaluate information and reach conclusions:

Idealistic lawyers and idealistic scientists often describe themselves as engaging in a search for truth.The scientists follow the scientific method. They state their hypotheses, describe the ways they test them, present their findings — and wait for another researcher to prove them wrong. Lawyers’ practice is built on the idea that the best way to shake the truth out of a complex dispute is for advocates on each side to argue it, as vigorously as they can, in front of an impartial judge or jury.

These approaches work more or less well on their own. But when a legal issue hinges on questions of science, they can clash. And the collision can resound all the way up to the Supreme Court.

On the occasion of its tenth Anniversary, the Project on Scientific Knowledge and Public Policy (SKAPP) issued a report on the Daubert decision: “Daubert: The Most Influential Supreme Court Decision You’ve Never Heard Of” (HTML excerpt or full report).

SKAPP also a convened a conference, bringing together a group of distinguished scientists, philosophers of science, judges and policy experts to present papers and discuss the use and misuse of scientific evidence in public policy, and the implications of Daubert. Papers by such luminaries as Sheila Jasanoff, Susan Haack and George Lakoff focused on how these issues are worked out in the legal and regulatory arena, with topics that included: what is the meaning of causation; how do scientists reach judgments; and is there a scientific method?

The papers presented at the conference and others on these topic s were published in a special issue of the American Journal of Public Health (Vol 95, S1, July 2005), and are available for free downloading on the SKAPP website.

In the lead editorial Scientific Evidence and Public Policy introducing the issue, I wrote:

Close analysis of the Supreme Court decision reveals a series of concerns. The requirements Daubert imposes on federal judges are unreachable–no absolute criteria exist for assessing the validity of scientific evidence. Scientific reasoning is no more susceptible to a mechanical approach than legal reasoning. Checklists of criteria, although appealing in their convenience, are inadequate tools for assessing causation. Alternatively, judges may rely on their own experience and “common sense,” which has inherent biases and limitations.

Compounding this problem, the Daubert decision provides nophilosophical tool to help judges identify “good science.” … It is, therefore, not surprising that judges are no better able to evaluate scientific evidence than groups of jurors, who use a deliberative process to pool their collective wisdom and assess the evidence presented to them……

[T]he criteria that make scientific claims valid within scientific settings are not easily transferable to legal settings. As Sheila Jasanoff writes, “the grand question for the law is not how judges can best do justice to science; the more critical concern is how courts can better render justice under conditions of endemic uncertainty and ignorance.”

The likelihood that questions of scientific validity are raised in a legal proceeding is related to the wealth of the parties involved. Indigent defendants in criminal trials, for example, are rarely capable of hiring experts to counter questionable science that purports to link them with a crime. In contrast, corporate defendants often hire teams of lawyers and scientific experts to use Daubert to make it difficult and costly for plaintiffs to put on their scientific cases through expert witnesses. The tobacco industry, for example, used its extensive resources to challenge the testimony of numerous expert witnesses; it recognized that driving up the costs to plaintiff attorneys would help insulate the industry from legal accountability for producing a dangerous product.

Overall, it appears that Daubert has likely discouraged plaintiffs without scientifically sound claims from pursuing them in court, whereas others with strong claims but insufficient resources have also been prevented from pursuing just compensation for injury.

In his dissent in the Daubert case, former Chief Justice William Rehnquist raised concern that Daubert would force judges, many of whom have little knowledge of science, to become “amateur scientists.”

Returning to last week’s Supreme Court session on global warming, it is understandable that Justice Scalia’s humorous acknowledgement brought laughter to the courtroom. But let’s also remember that the implications of the Daubert decision are very serious.

David Michaels heads the Project on Scientific Knowledge and Public Policy (SKAPP) and is Professor and Acting Chairman in the Department of Environmental and Occupational Health, the George Washington University School of Public Health and Health Services.

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