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13 Cardozo L. Rev. 303 (1991 - 1992)
Some Caveats Concerning DNA as Criminal Identification Evidence: With Thanks to the Reverend Bayes

handle is hein.journals/cdozo13 and id is 325 raw text is: SOME CAVEATS CONCERNING DNA AS CRIMINAL IDENTIFICATION EVIDENCE: WITH THANKS TO THE REVEREND BAYES Richard Lempert* INTRODUCTION The conference panel at which this paper was originally presented was structured along the lines of a debate. The three speak- ers who were supposed to advocate the use of DNA evidence were labeled, as is customary, Proponents. But those who were supposed to take the negative side were not called Opponents. Rather they were labeled Caveators. I do not know who is responsible for this label,' but I think it gets things exactly right. To my mind anyone consider- ing DNA as criminal identification evidence should be a Caveator. The promise and utility of DNA analysis in identifying the perpetra- tors of such serious crimes as rape and homicide must be acknowl- edged, but one must also be aware of the limits of the DNA identification process as it now exists and the ways in which these limits affect what experts can reliably tell judges and jurors. In partic- ular, I shall argue below that current practices may lead to misleading claims for reasons that to date have not been fully appreciated by the forensic science community. In making some of these arguments I shall use the Bayesian perspective which Finkelstein and Fairley2 long ago posited as a paradigm for thinking about identification evidence. Although the forensic use of DNA to identify criminals is in this country less than five years old, the law review literature is already replete with articles discussing the technology.' Many of these arti- * Francis A. Allen Professor of Law, University of Michigan Law School. B.A., 1964, Oberlin College; J.D., 1968, Ph.D., 1972, University of Michigan. Work on this paper was supported by the Cook funds of the University of Michigan Law School. I especially thank Ian Evett and William Thompson who commented helpfully on the initial version of this paper and who provided me with material that was of great aid as I revised. This version of the paper is, however, very different from the version they saw, and there is no reason to expect that they would agree with everything I have written. I am also grateful to Sam Gross and Larry Kramer for their helpful comments on this manuscript. I I assume Peter Tillers who organized the conference is responsible for the label, but I never went so far as to ask him. 2 Finkelstein & Fairley, A Bayesian Approach to Identification Evidence, 83 HARV. L. REV. 489 (1970). 3 See, e.g., Thompson & Ford, DNA Typing. Acceptance and Weight of the New Genetic Identification Tests, 75 VA. L. REv. 45 (1989); Note, The Dark Side of DNA Profiling: Unrelia-