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Comparison of Allelic Variation and Statistical Properties of RFLP Versus PCR-Based DNA Profiles Final Report

NCJ Number
Date Published
January 1996
9 pages
Goals of this study were to collect and analyze data on DNA typing results and to address questions regarding the power and reliability of methods for calculating the probability of DNA matches.
The study found that different types of DNA markers, such as variable number of tandem repeats (VNTR's), short tandem repeats, and microsatellites, showed different modes of evolution, but differences were too slight to affect forensic calculations. The study developed novel measures of genetic distance to evaluate differences between populations. These measures demonstrated that any biases in measuring population frequencies were either too slight to affect forensic calculations or were always conservative and benefitted the defendant. In addition, the study established the minimal size of a reliable data sample (approximately 100 to 150 individuals) and evaluated the occurrence and consequences of null or overlapping VNTR alleles. It was determined that most current data sets used in forensic cases are of adequate size. Further, the study developed a technically correct method of determining confidence intervals in calculating the probability of DNA matches, in order to deal with limited sample sizes. Finally, the study demonstrated that the presence of population substructure does not pose any problem in providing conservative forensic calculations. 38 references

Date Published: January 1, 1996