[A method to calculate the probability of paternity between relatives--a paternity case where the putative father was a deceased granduncle].

To test paternity in a case where the putative father was a deceased uncle of mother (plaintiff's granduncle), we designed a new method to calculate the probability of paternity likelihood. The putative father's genotypes of red cell antigens, HLA and short tandem repeat (STR) polymorphism were estimated from those of mother and sister of the plaintiff. When the probability was calculated from the frequencies in the unrelated individuals (the standard method), a significant bias might be introduced since the putative father and the plaintiff were likely to have the same alleles come from their common ancestry. Therefore, we designed a new method to calculate the likelihood ratio from the frequencies in the group of mother's uncles estimated from mother's genotypes. The probability (0.9299) calculated with our method was found to be lower than that (0.9992) done with the standard method indicating that the new method could remove the bias introduced from the incest.