과학적 증거의 증거능력 판단에 관한 소고

The emergence of genetic science poses significant challenges at both the substantive and procedural levels of litigation. The use of scientific proof in a forensic setting has proven problematic for both judges and attorneys because most of them are not technically trained. Much of the difficulty encountered by courts when facing scientific evidence lies not in a lack of understanding the underlying science but in the task of choosing between competing scientific explanations tendered by individuals who seek to wear the mantle of experts. Judicial discomfort in handling scientific evidence has increased in recent years with the emergence of scientific testimony offered by experts whose availability and malleability have earned them the sobriquet of hired guns. Just as the controversy over roving experts was at its height, the role of judges in determining the admissibility of scientific and technical evidence was made more difficult by the 1993 U.S. Supreme Court’s decision in Daubert v. Merrell Dow Pharmaceutical, Inc., which abolished the seventy-year-old test for evaluating scientific evidence first pronounced in Frye v. United States. Under Frye’s simplistic teaching, trial courts, when faced with a challenge to the admissibility of expert testimony, determined whether the expert’s methods were generally accepted in the relevant scientific community. If so, the evidence was admitted with any deficiencies attributable to either the frailty of the underlying science or the expert’s qualifications, both matters of weight for the jury. The underlying evidentiary issue in Daubert was the scientific validity of the methodology of studies offered by the plaintiffs to prove that a drug used by pregnant mothers to control nausea could cause birth defects. In considering that matter, the Supreme Court unanimously ruled that Frye did not survive the enactment of Federal Rule of Evidence 702, and some other approach was necessary. A majority of the Court then ruled that when confronted with novel or scientific evidence, the trial judge must assume the role of gatekeeper to ensure that the expert’s testimony both rests on a reliable foundation and is relevant to the task at hand. In discharging the reliability task, the trial judge may use a variety of sources, including the testimony of experts. However, ultimately it is the trial judge’s decision whether the evidence passes the test of reliability. Although the language of the majority opinion in Daubert appears to confer broad discretion on trial judges, it emphasizes the need to determine the reliability of scientific knowledge through its origin in the scientific method. To that end, the Supreme Court directed trial judges to consider at least four factors when determining admissibility: (1) whether the theory or technique can be tested, (2) whether the proffered work has been subjected to peer review, (3) whether the rate of error is acceptable, and (4) whether the method at issue enjoys widespread acceptance. As areas of scientific inquiry advance, the judicial system will be challenged to accommodate this new knowledge while not abandoning the safeguards of relevancy and reliability. Both trial judges, as gatekeepers of admissibility, and appellate judges, as definers of the standards of proof, will be required to acquire new learning in fields unfamiliar to them. Unless these challenges are met, the judicial system may find itself unable to cope with the demands of modern litigation and the latest forensic techniques.