Courts in the United States process huge quantities of scientific information. Every day, they must determine the validity of expertise ranging from acoustics to zoology, in matters ranging from civil slip-and-fall cases to criminal prosecutions that may result in prison sentences or even execution.
In federal courts and in virtually all states, judges are expected to be “gatekeepers,” responsible for assessing the validity of the scientific or technical expert testimony offered by the parties. Judges are expected to distinguish the scientific wheat from the pseudoscientific chaff. Yet most judges do not have the ability to fulfill this responsibility adequately. They have little or no background in science. Indeed, many went to law school because they were straight-A students in history or sociology but had no appetite for biology or statistics. As a practical matter, judges have largely failed in carrying out their responsibilities to evaluate the science offered in their courtrooms. But the problem of gatekeeping in research was solved by scientists long ago. That solution is peer review.
Historically, courts have adopted two basic approaches to the challenge of assessing validity at the courthouse door. One is the test associated with Frye v. United States, a 1923 case that calls upon judges to assess the general acceptance of the proffered science in the “relevant scientific community.” The second is associated with the 1993 landmark United States Supreme Court decision in Daubert v. Merrell Dow Pharmaceuticals, Inc., which requires federal judges to evaluate the methods and principles underlying expert evidence. Both tests establish courts as gatekeepers against junk science. Good science goes to the jury to weigh when considering the merits of the case, while bad science is shown the door. Unfortunately, however, most judges do not have the capacity or resources to effectively employ either test. They have no mechanism to actually survey mainstream scientific opinion; and judges who cannot distinguish a median from a mode are unlikely to handle multiple regression analysis with confidence.
The question is, how do we provide judges a mechanism by which to assess mainstream scientific opinion? Peer review works for science, but can it work for the courts? Properly done, peer review nearly always involves some level of anonymous evaluation by scientists actively engaged in similar research. If the law could access a similar system of independent evaluation to assess the methods and principles underlying expert testimony, it would produce a host of benefits. It would give courts a window into the mainstream views of the respective scientific field, and the reports of peer reviewers would provide neutral evaluations of the bases for the expert opinion. Over time, if peer review becomes an accepted—or expected—process, the party experts themselves will likely better conform their own opinions to those of the mainstream.
Admittedly, peer review suffers from many limitations. It is inherently conservative, tends to reinforce dominant views in the field, and may be unduly restrictive when brought to bear on certain fields of study. But from the law’s perspective, these limitations are virtues. The law is, at bottom, a fairly conservative enterprise. In the domain of scientific evidence, courts are ill-suited to distinguish between promising hypotheses that will eventually gain acceptance and those destined for the junk heap. And for all its shortcomings, no one in science advocates the abandonment of peer review. The current trend, in fact, is to call for more of it.
The same process can easily be adapted to evaluate expert testimony, with independent, anonymous scientists acting as peer reviewers, just as they do for scientific journals. It might be that scientists would be reluctant to get involved with courtroom proceedings. But they should care how their science is used, misused, or ignored by the courts. After all, the law employs science daily, with or without mainstream scientists’ participation. Scientists who agree to participate in peer review of proffered expert testimony can ensure that their fields are not misrepresented. Scientist peer reviewers do not themselves get embroiled in litigation, because they do not operate as experts for either party. The reviews are done independently and not in anticipation that they are serving any particular side in a dispute. And not to be entirely discounted, reviewers are paid for their work.
Although courts are not currently constituted to incorporate peer review into their admissibility decisions, such processes could be readily adopted by both lawyers and judges. For lawyers, independent and neutral evaluation through blind peer review would give them the traction to challenge opposing experts who stray beyond the bounds of accepted opinion or defend their own experts against such objections.
However much peer review processes might empower attorneys, the real beneficiaries of the independent perspectives offered by mainstream scientists are the courts. Currently, the only similar mechanism available to courts are appointed experts, an expensive and controversial method. When confronted by battling experts, peer review provides judges with the independent perspective they need to evaluate conflicting opinions. In civil litigation, the relatively modest costs would be borne by the parties and their testifying experts would be given the opportunity to respond to the reviews. Admittedly, criminal cases present greater challenges, because there are fewer resources available. Nonetheless, courts and prosecutors typically have modest budgets available to support expert testimony and some of these funds could be redirected to finance peer reviews.
Peer review has the potential to provide judges a sorely needed window into mainstream science. Through that window, courts are able to see the bases for expert evidence and are able to assess its level of acceptance within the scientific community. Accordingly, it is time that peer review, an age-old solution to scientific assessment, is brought to bear on the perennial problem of bringing scientific sensibilities into the law.