Identifying victims of the largest Second World War family massacre in Slovenia.

The killings during the Second World War, with nearly one hundred thousand victims, is one of the greatest losses of life in Slovenia's modern history. This article presents the genetic identification of the victims of the largest family massacre that occurred in Slovenia, in which 10 members of the same family were killed. Seven of them were buried in a hidden mass grave and only two children survived. In 2015 and 2016, two graves were found and three incomplete female skeletons and at least three incomplete male skeletons were exhumed. A total of 12 bones and teeth were analysed and compared to two living relatives. Extracted DNA was quantified using the PowerQuant kit, and various autosomal and Y-STR kits were used for STR typing. Up to 2.7 ng DNA/g of powder was acquired from the samples analysed. We managed to obtain nuclear DNA for successful STR typing from seven bones and one molar. From the female grave, autosomal profiles were obtained only from one skeleton, and from the male grave from five out of six femurs. The relationships between the males were additionally confirmed by analyses of Y-STRs. STR profiles made possible the identification of four family members; one of the aunts from the female grave, and two uncles and the father of the surviving children, who were used as family references, from the male grave. The product rule was used to calculate a combined likelihood ratio for autosomal and Y-STRs, and statistical analyses showed high confidence of correct identification with posterior probability (PP) greater than 99.9 % for three out of four victims identified. For identifying the aunt, the PP obtained after ESI-17 and NGM STR typing was too low. To increase the PP, the next-generation sequencing Precision ID GlobalFiler NGS STR Panel was used and, after the analysis of additional STR loci, the statistical analysis showed a PP greater than 99.9 %, indicating that a sufficient number of genetic markers had been investigated in identifying the skeletal remains of the aunt. An elimination database containing the genetic profiles of all individuals that had been in contact with the bones was created to ensure traceability in case of contamination, and no matches were found. After more than 70 years, the skeletal remains were returned to the surviving children, who buried their relatives in a family grave.