Jenifer A.L. Smith, Ph.D., Alan M. Guisti, MS, and Bruce Budowle, Ph.D.
FBI Laboratory

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In May of 1996, a second committee formed by the National Research Council issued a report that clearly supported the current technologies used by the forensic DNA community. Comprehensive review of numerous resources resulted in conclusions such as "The technology for DNA profiling and the methods for estimating frequencies and related statistics have progressed to the point where the reliability and validity of properly collected and analyzed DNA data should not be in doubt." They clearly rejected the ad hoc "ceiling principle," strongly endorsed the binning approach and put issues such as "laboratory error rates," to rest. In addition to this powerful endorsement of the forensic DNA community’s current practices, they addressed the issue of "uniqueness". They state, "The definition of uniqueness is outside our province. It is for the courts to decide, but in case such a decision is to be made, we show how to do the relevant calculations." With available testing procedures, interpretation of data can lead to identification of an individual as a source of a particular stain. Attorneys may question and judges may decide the admissibility of these determinations but it is within the purview of the scientist to report the identification. To this end, the DNA Analysis Unit (DNAU-I) of the FBI Laboratory will uniquely identify an individual as the source of a particular body fluid stain using RFLP profiles consisting of six to eight matching loci. This presentation will detail the statistical approach and calculations practiced by the DNAU-I.