Belarusian experience of the use of FamLinkX for solving complex kinship cases involving X-STR markers

Abstract Use of X-STR markers extends and gives additional possibilities to a forensic DNA expert for kinship analysis. FamLinkX is software for the calculation of likelihood ratios (LRs) for kinship cases based on X-STR DNA profiles that takes linkage and linkage disequilibrium as well as mutations of X-STR markers into account. Belarusian haplotype frequencies database of 360 unrelated Belarusian males has been uploaded to FamLinkX. LR values for 6 deficient paternity cases and 2 forensic cases involving two putative full siblings, females, were calculated with different values of lambda ( λ =1, 10, 100) in order to account for uncertainties in the haplotype frequency estimation. To demonstrate the ethnic sensitivity of X-STR markers and importance of the choice of the appropriate X-STR population database for LR calculation we calculated LR values for the same kinship cases using Belarusian and Swedish X-STR databases. LR values for the same kinship case differed from each other up to 6000 times depending on the chosen database. X-STRs genotyping lets us to determine relatedness successfully in all cases whereas the results of autosomal STR profiling and mitochondrial sequencing (for the cases where only the samples of putative full-siblings were available) were not sufficient to resolve family relationships issues. LR values were considered to be high enough in all cases.