Neuropsychiatry at the Courtroom Gates: Selective Entry or Anything Goes?

That the influx of technology into our lives will include its entry into law and legal proceedings is a foregone conclusion. "Progress" of this kind can be slowed or regulated, perhaps, but it cannot be stopped. The proposed use of positron emission tomography (PET) scan-derived data on brain functioning in a criminal insanity case is merely one of the latest efforts to put biotechnology to forensic use. How the court reacts to this particular admissibility proposition-in or out?-may serve as a useful example of how the larger battle is fought. Trial judges are the gatekeepers in our legal system. They make the initial decision as to whether a piece of controversial evidence, scientific or otherwise, may go to the jury. Trial judges are under pressure to admit innovative factual evidence or theory from several sources, among which trial attorneys, the purveyors and practitioners of the new techniques, and the law itself (as personified by the "progressive" rulings of appellate judges or legislators) are the more obvious. The 1975 Federal Rules of Evidence exemplify the success of this sort of pressure. Pertaining to the admissibility of evidence generally and of scientific evidence in particular, the Federal Rules are clearly more liberal in intent and effect than was the doctrine that preceeded them: the 1923 Frye rule, which required "general acceptance" of the proffered new technology or theory. In the recent case of Daubert v. Merrell Dow Pharmaceuticals, however, the U.S. Supreme Court has let it be known that standards of reliability continue to be in force for scientific evidence submitted under the Federal Rules and that gatekeeping remains an important function of the trial judge. Nonetheless, a "sleeper" rule permitting experts to support the opinions they offer in court with reasonable clarifying information opens the evidentiary door a bit wider than the restrictions of Daubert might suggest. In the case at hand, this rule led to a preliminary decision that PET scan data concerning the defendant could come in, despite the lack of a scientifically established connection between such data and the criminal behavior at issue. This particular result is probably a bad one. Does that mean PET scan evidence in the courts is an example of general forensic misuse of neurotechnology? Are the new admissibility rules hopelessly out of whack? There is no need for such broadsides. The better conclusion is that neuropsychiatrists should continue to work together with lawyers and lawmakers to ensure, as much as possible, the appropriate application of this technology to legal proceedings.