Microsatellite typing in a paternity case against a deceased man whose two brothers were available for testing

To resolve a deficiency case of disputed paternity, we examined the mother, child, and two sibs of the deceased alleged father. In all of the 11 conventional marker systems and three microsatellite systems (ACTBP2, FGA, and D11S488) applied, the child and the paternal sibs had alleles is common. We deduced first the possible ACTBP2 genotypes of the deceased parents of the two sibs from their test results. Next, from all the combinations of the deduced genotypes, we estimated the frequencies of the possible genotypes of the alleged father and, with Bayes' theorem, calculated the probabilities of the alleged father having the genotypes compatible with paternity. Using these probabilities, we worked out the probability of the child's genotype resulting from the mating of the mother with the alleged father. Meanwhile, we calculated the probability of the child's genotype being expected of the mating of the mother with an unrelated random man. Finally, applying Bayes' theorem again, we obtained a probability of paternity of 0.992 for the ACTBP2 locus alone. Inclusion of the FGA locus in the probability calculations brought the overall probability of paternity to 0.998. The present study demonstrates that testing for hypervariable microsatellite loci greatly facilitates the solution of a deficiency case that would be difficult or time-consuming to solve by conventional marker typing.