A new framework to test parent-child and full sibling relationships with population substructure

Familial search is a statistical approach that is used to infer genetic relationships between a forensic sample and individuals in a DNA database. Several authors have proposed likelihood ratio-based statistics for testing parent-child and full sibling relationships when population substructure exists. This paper proposes three new statistics and investigates performance of each statistic based on Type I error and power. Three statistics, defined by (1) the local allele frequency, (2) the Balding-Nichols approach and (3) the ratio between the maximum of the genotype probabilities over racial subgroup, were found to be good for testing these two types of familial relationships. Power analyses within racial groups are also included, with the power highest for African-American samples and lowest for Caucasian samples. Finally, simulation studies were done on both original and extended CODIS core loci. There were clear differences in power, with the power substantially higher for extended CODIS core loci.