Saturday, September 5, 2009

Scientific witness in the courtroom

This past June the U.S. Supreme court issued a decision with fascinating ramifications for the notion of scientific authority. They ruled that reports from crime laboratories may not be used at trial against a criminal defendant unless the analysts responsible for creating the data are present to give testimony and bear cross-examination. This decision is an interpretation of the Sixth Amendment, which provides in part that an accused has the right “to be confronted with the witnesses against him. “

The case brought before the court arose from the conviction of Luis E. Melendez-Dias on cocaine trafficking charges. Part of the evidence against him was a laboratory report stating that bags of white powder allegedly belonging to Melendez-Dias contained cocaine. The lab report was submitted by prosecutors with an analyst’s certificate, but no analyst appeared to give testimony.

Adam Liptak, reporting in the New York Times on the court decision, notes the unusual way in which the court divided on the 5-to-4 decision. With the majority were Justices Scalia, Thomas, Stevens, Souter and Ginsburg. Dissenting were Justice Kennedy who wrote vigorously for the dissenters; Roberts, Alito and Breyer. This was no ordinary cleavage along conservative/liberal lines! Scalia, writing for the majority, took the view that defendants had the same right to confront adverse expert testimony as they enjoy with respect to any other form of testimony. Kennedy, in dissent, pointed to the huge disruptions that might occur in court cases if every laboratory report needed to be brought to the court by a bona fide representative of the laboratory making the report; that is, a real analyst who could as needed provide expert background testimony. However, according to Jeffrey L. Fisher, a law professor at Stanford, who represented Mr. Melendez-Dias, about a third of states already follow procedures that comply with the new decision.

The court’s decision raises several questions that are of importance for science’s relationship with society. The first level at which to approach this is to ask whether there is a matter here at all of science’s epistemic, or expert, authority. Justice Scalia, in his majority opinion wrote that the Constitution would require allowing defendants to confront witnesses even if “all analysts always possessed the scientific acumen of Mme. Curie and the veracity of Mother Teresa.” In other words, even assuming that the crime lab results are of the highest scientific quality, and that the reporter is a person of impeccable moral standards, the Constitution requires that the defendant have the opportunity to confront the witness. But of course not all crime lab personnel are fully competent, free from making errors of various kinds, or always above suspicion of reporting results tilted toward the prosecution’s case. In these respects, cross examination of a witness reporting forensic results is of a kind with cross examination of any other witness. It really doesn’t go to the question of whether the scientific principles and applied technology that undergird the reported results are sound and relevant to the evidence being presented. Nor does it cover the question of whether the laboratory has obtained the results through full and competent observance of all the required protocols.

There is plenty of reason to be concerned regarding the quality and veracity of much forensic evidence. The National Academies of Science in February of this year issued a report on the state of forensic science in the US, and on what steps might be taken to strengthen it. Quoting from the report’s executive summary, “…in some cases, substantive information and testimony based on faulty forensic science analyses may have contributed to wrongful convictions of innocent people. This fact has demonstrated the potential danger of giving undue weight to evidence and testimony derived from imperfect testing and analysis. Moreover, imprecise or exaggerated expert testimony has sometimes contributed to the admission of erroneous or misleading evidence.” Defense counsel thus may have plenty of grounds for questioning the technical witness that brings forth the forensic evidence. It may be a good strategy to question the basic scientific assumptions underlying the methods employed. On the other hand, when the matter at hand is fairly simple, raising too many questions can be a poor strategy in that it merely serves to call attention to the results. In any event, the defense now possesses a power it had not previously had. Justice Kennedy and the other dissenting justices seem to be very concerned about cases where the analyst may not be available, or where over the passage of time the analyst may have retired, changed jobs and so forth. These are legitimate concerns, but they seem to me to pale in comparison with the prospect of defendants facing a written laboratory report without any means of cross examining the person or persons responsible for the analyses.

It is not always easy to keep the non-scientific world attuned to the notion that the doing of science, even at the level of often mundane analysis of forensic materials, is a human activity. Science is not really about objective truth in some abstract and disembodied sense. It is about kinds of truth found in the course of looking at aspects of the world with a certain kind of eye, with a certain ethic of disinterestedness. That sort of work is done by humans. Even given the best of intentions, errors may be committed, omissions may occur. When scientists report to the larger society on what they have done they should not be perceived as oracles, presenting something drafted by Gods. It is one of science’s shortcomings that is has not engaged the larger society as fully as it should, that science is not seen as the product of human endeavor. Yes, the social structure of science does go a long way toward weeding out errors and falsifications during the formation of new knowledge, but in the day-to-day applications of science, as in a forensic laboratory, human nature is at work. When someone’s future may hang on the outcome of courtroom deliberations, the human who has generated scientific evidence that bears on the case should be there to testify to it.

No comments:

Post a Comment