Opinion ID: 629046
Heading Depth: 2
Heading Rank: 1

Heading: DNA Profiling

Text: 11 Before examining the standard of admissibility, we shall outline the process of DNA identification profiling. 5 The process of DNA profiling identification involves, broadly speaking, two steps. First, the scientist compares DNA from a known sample with DNA from an unknown source. The DNA is compared at several different points, to see if the DNA pattern in the unknown sample at each specific point matches the DNA pattern in the known sample at each specific point. The scientist will declare a match only if all DNA segments compared on the two samples are identical, i.e., show the same pattern, within a certain range of error. 12 Finding a match is not, however, the end of the procedure. A DNA match merely tells the scientist that the person who contributed the known sample is a potential contributor of the unknown sample. The second step of the DNA identification process then involves a determination of the probability that someone other than the contributor of the known sample could have contributed the unknown sample. 13 To do this probability analysis, the scientist compares the tested samples against information about the general population. The FBI and other laboratories have done experiments to determine the frequency with which certain DNA patterns appear in different racial and ethnic populations. By reference to these studies, the scientist determines the frequency with which each DNA pattern appearing on the known sample exists in the population from which the known sample comes. After determining this probability for each of the DNA segments tested, the scientist multiplies the probabilities of each of the segments tested to determine the probability that someone in that population would have identical patterns on all the DNA segments tested. For example, if 50% of the population had the pattern the known sample showed at test site A, 50% had the pattern the known sample showed at test site B, 50% had the pattern the known sample showed at test site C, and 50% had the pattern the known sample showed at test site D, the probability that any one member of that population would have all four of those patterns would be .5 X .5 X .5 X .5, or 6.25%. Expert testimony in DNA profiling cases is generally expressed in these terms. For example, the expert will testify that probability studies demonstrate 1 in 2600 American Indians would be expected to produce a matching sample. 14 DNA profiling is still relatively new as a forensic tool and has been the subject of heated controversy in both the legal and scientific communities. However, it is generally conceded that the principle of DNA profiling is recognized as reliable and that the procedures are not so new or novel as to warrant disagreement. People v. Castro, 144 Misc.2d 956, 545 N.Y.S.2d 985 (N.Y.Sup.Ct.1989) (clearly established unanimity). Other commentators have stated:There is nothing controversial about the theory underlying DNA typing. Indeed, this theory is so well accepted that its accuracy is unlikely even to be raised as an issue in hearings on the admissibility of the new tests. 15 Thompson & Ford, DNA Typing: Acceptance and Weight of the New Genetic Identification Tests, 75 Va.L.Rev. 45, 60 (1989). See also U.S. Congress, Office of Technology Assessment, Genetic Witness: Forensic Uses of DNA Tests 7-8, OTA-BA-438 (Washington, D.C.: U.S. Government Printing Office, July 1990) (stating that DNA profiling is valid and reliable in forensics where procedures are properly performed and analyzed). Nevertheless, beyond the theoretical level, concerns persist over possible error and ambiguity. The problems arise at two levels: controlling the experimental conditions of the analysis and interpreting the results. McCormick on Evidence Sec. 203 at 900-01 (4th ed. 1992). 6 Clearly, the procedures are extraordinarily complex and the rigors of forensic probability calculations cannot be trivialized. Super-impose on these concerns the effect of the evidence in a criminal trial, and the dilemma posed is clear. One commentator has suggested: 16 [w]henever novel scientific evidence is offered in court, the legal system faces competing concerns. One [sic] one hand, there is a danger that excessive caution will prevent valuable evidence from being admitted in a timely manner. On the other hand, there is a danger that evidence accepted quickly and uncritically will later prove less reliable than promised. 17 Thompson & Ford, DNA Typing, Trial at 64 (Sept.1988). There is no consensus among the state courts which have considered the admissibility of DNA evidence. However, with notable exceptions, the tide seems to be turning in favor of general admissibility. 7