False inclusion in a deficient paternity case with two alleged fathers

Abstract

We present a case of deficient paternity with two presumptive fathers analyzed with 19 Autosomic STRs and resolved by means of the study of 12 Y-chromosome STRs. This is case PA-GYQ-62-06, in which two presumptive fathers disputed the paternity of a male child and the mother was not available. The presumptive fathers are not genetically related to one another and the three individuals studied are males of Mestizo origin, born and residing in Ecuador. Fifteen autosomic STRs consensued from the commercial kit PowerPlex-16 ® (Promega) were analyzed and a combined paternity index (PI com) of 13,811.215 and a probability of paternity ( W) of 99.9999928% were obtained for presumptive father 1 and a PI com of 35,332.241 with a W of 99.9999971% for presumptive father 2, which meant that inclusion was found for both fathers. We amplified the study with the FFFL ® (Promega) system, whereby an exclusion was found in the HUMLPL marker between presumptive father 1 and the son, possibly involving a first-order mutation. These results did not enable us to exclude either of the two fathers. Due to the importance of the case, 12 Y-chromosome STRs were analyzed with the commercial PowerPlex-Y ® kit, which led to the exclusion of presumptive father 1 due to the fact that he displayed a different haplotype; in this pair, exclusion of the HUMLPL was also found.