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120 The FBI’s success in gaining control of DNA profiling quickly attracted the attention of a few defense attorneys who were deeply skeptical that the bureau’s testing regime was any better than those of Lifecodes or Cellmark. Because the tactics used against the private labs—that is, making a strong distinction between forensic and nonforensic uses of the technique—achieved only limited success in court, the defense decided to focus on the population genetics issues that had played a secondary role in early cases such as Castro and Schwartz. In a series of trials culminating in the Toledo, Ohio, federal court case of United States v. Yee, et al. (134 F.R.D. 161, 1991), the defense community argued that the method used by the bureau to calculate the probability of a random match between a suspect’s DNA profile and the DNA profile found at the crime scene was dangerously flawed. Their central claim was that the bureau did not adequately take into account a phenomenon called “population substructure” when estimating the rarity of a given genetic marker within the major racial groups—the reference population used in forensic casework to determine the rarity of a particular allele. Instead, they assumed that all major ethnicities within a given race, such as Swedes, Norwegians, Irish, Jewish, and Italian in the Caucasian racial group, tend to intermarry and have gene frequencies that do not diverge significantly from the group average. Although these subpopulations may have slight differences from the overall racial profile, for the FBI and their supporters, these deviations were only of academic interest and did not affect the kinds of probability calculations made in forensic casework. Making this assumption allowed forensic scientists to carry out simple probability calculations that did not correct for the possibility that the donors of the two DNA profiles being compared belonged to a subtype more genetically similar than the Caucasian population as a whole. The defense and their experts argued that the probability of a random match would be significantly higher if two donors belonged to a subpopulation of individuals with a lower level of The DNA Wars  c h a p t e r 6 Chap-06.qxd 6/28/07 10:00 AM Page 120 the dna wars 121 genetic diversity than the larger reference population being used for the probability calculation, because they are more likely to share particular combinations of alleles in common. After Yee, race and population genetics became the dominant source of controversy surrounding DNA evidence in the American legal system, leaving many of the issues that arose in Castro and other previous cases unresolved. It is important to note that this controversy did not emerge from the scientific community. Instead, lawyers—most notably Barry Scheck and Peter Neufeld—generated disagreement about population genetics by constructing an alternative set of expert witnesses with which to challenge claims made by the prosecution and their witnesses. In Yee, as in previous cases involving the private companies, prosecutors sought to control the relevant scientific disciplines and legitimate experts involved in the evaluation of DNA evidence, a process that sociologist of science Thomas Gieyrn has labeled “boundary work.”1 In this case, prosecutors argued that the human genetics community was the “relevant scientific community” to testify in court about the validity and reliability of the FBI’s interpretation of DNA profiles. Scheck and Neufeld, on the other hand, sought to convince the judge that the relevant scientific community was much broader, encompassing individuals whose work was not directly related to the study of human populations or forensic investigations.They used this same tactic with significant success in Castro when they had Eric Lander qualified as an academic scientist who was knowledgeable enough about forensic science to be considered an expert by the judge,even though he was not considered to be part of the forensic science community itself.The prosecution and its allies sought to counter these moves by co-opting the strategy that Scheck and Neufeld used in their early challenges to prosecution experts testifying on behalf of the private companies’ DNA typing regimes. As important as the minutiae of population genetics were to the outcome of Yee, there was much more at stake in this case and the controversy that emerged in its wake. Most important, the prosecution and defense were doing battle over the identity of the expert witnesses. Not only did the...

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