ADDITIONAL ANALYSIS OF CROATIAN POPULATION STRUCTURE AND COMMENTS ON IDENTIFICATION OF REMAINS IN MASS CASUALTY DATABASES: POWERPLEX 16 DATABASES FOR SOUTHERN CROATIANS
The validation of a Powerplex 16 (PP16) database for southern Croatians provided the opportunity to address questions raised by Birus et al (1) regarding the occurrence of linkage disequilibrium and false matches. The PP16 database had no significant deviations from HWE and were not significantly different from the previous study of the 13 shared CODIS loci (2) indicating that the two data sets could be pooled. A test for two locus linkage disequilibrium did not yield any unexpected significant correlations precluding any higher order disequilibrium. The power of exclusion (RPNE) (3) in a parentage test assumes that a single comparison is being performed. When using parents or children to identify remains the exclusionary power using either allele is very low compared to using separate alleles, e.g. using the pooled Croatian database with the two most common alleles at each locus the combined RPNE for 15 loci when using two alleles is only 0.011, compared to an RPNE of 3.24E-11 when using separate alleles, or a random match likelihood using the same alleles of 9.3E-14. Thus, the likelihood of false matches when making large numbers of comparisons is very high, making it necessary to either compare multiple relatives to profiles, when a hit is made, or correct the expected RPNE for the number of comparisons made to get an estimate of the true RPNE.