ISSN: 0022-1198
CODEN: JFSCA
Published Online: 1 September 2004
Page Count: 6

Matching and Partially-Matching DNA Profiles
Weir, BS
North Carolina State University, NC

(Received 8 February 2003; accepted 3 April 2004)

Abstract

The DNA profiles of two individuals can have 0, 1, or 2 pairs of alleles that are the same at each locus. These events may be called mismatches, partial matches or matches, respectively, and they have probabilities that depend on the population proportions of alleles as well as the population structure parameter theta. The observed and expected numbers of pairs of individuals with various numbers of matching or partially matching loci in FBI and Australian databases are found to be in good agreement provided theta is set equal to some small value greater than zero. The likelihood ratios for two individuals having a specified degree of relationship versus being unrelated also depend on the numbers of matching and partially matching loci, but even unrelated pairs of individuals can have likelihood ratios that support hypotheses of relatedness. Matching probabilities allow predictions to be made for the sizes of databases that are expected to contain a pair of individuals with high numbers of matching loci. It is very likely that two individuals with at least 9 matching loci among the 13 CODIS loci have already been typed.

Keywords:
forensic science, matching DNA profiles, population structure, relatedness, Australian DNA data, FBI DNA data

Paper ID: JFS2003039
DOI: 10.1520/JFS2003039
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