Forensic efficiency evaluation of a novel 22-STR panel for kinship testing in Eastern Chinese Han population

Short tandem repeats have been essential and fundamental genetic markers used in forensic individual discrimination and paternity testing since their discovery, especially those used in the Combined DNA Index System. Nevertheless, in cases of complex kinship identification, such as full-sibling, half-sibling, and uncle-niece relationships, the combined application of additional short tandem repeat loci is necessary to reach reliable identification conclusions. In this study, we evaluated the efficiency of an updated novel short tandem repeat genotyping system for kinship identification in the Eastern Chinese Han population. This 23-plex short tandem repeat system demonstrated strong discrimination power among individuals in the target population, with a combined power of discrimination and cumulative probability of exclusion of 1-2.107 1 × 10^-27 and 0.999 999 999 800, respectively. When 74 short tandem repeats were used and the threshold log₁₀(likelihood ratio) was set to 4, the system efficiency reached 0.999 9 and 0.707 3 for simulated full-sibling and half-sibling pairs, respectively. Furthermore, in two real secondary kinship identification cases, incorporation of the novel 23-plex short tandem repeat system increased the probabilities of the prior kinship hypotheses from 154.259 5 and 1 031.699 5 to 56 597.118 4 and 134 829.791 5, respectively, yielding reliable identification conclusions. Hence, it is evident that the novel 23-plex short tandem repeat system has notable potential as a tool for forensic kinship identification in the Eastern Chinese Han population and could serve as a complementary set of short tandem repeat loci for the identification of distant kinship.