NCJ Number
207180
Journal
Journal of Forensic Sciences Volume: 49 Issue: 5 Dated: September 2004 Pages: 1009-1014
Date Published
September 2004
Length
6 pages
Annotation
This note examines the "ibs" (two pairs of DNA alleles identical in state) probabilities for pairs of individuals, with attention to the circumstance in which any two alleles in the population have a probability ("theta") of being identical by descent (ibd).
Abstract
The author uses these probabilities to determine the expected number of DNA profiles that match or partially match at various number of loci. These numbers are compared to those observed in FBI (13 CODIS loci) and Australian forensic databases. The number of pairs of profiles in the FBI data is too low to permit useful statements beyond three loci. A larger set of nine-locus short tandem repeat (STR) profiles has been developed by Australian forensic agencies. This set is composed of people of various ethnic backgrounds, including Asian, Australian Aboriginal, Caucasian, and Maori. The probabilities allow a prediction of how large a database should be before a high number of matching loci can be expected. Although partially matching DNA profiles may suggest a kinship between two individuals, the numerical results suggest caution in inferring relatedness. Any statements on relatedness in such cases are best framed in terms of matching and partially matching loci rather than the total number of shared alleles. 5 tables, 1 figure, 8 references, and appended supplementary mathematical equations and a table that shows the probabilities of all possible pairs of genotypes in terms of allele frequencies and theta