Statistical analysis of DNA mixtures using peak area information and allelic drop out

A case of a woman killed in Perugia is reported. The woman was beaten to death and the body showed evidence of bites, kicks and punches. The request of the Court was to verify the presence of bites and if they belonged to humans. Morphological examination and genetic analysis with human Y-specific markers were performed in order to verify the origin of the bites. The DNA profile from the surrounded area of the traces was compared with the profile of the victim's husband (the suspect).The results showed a match between the profile of the suspect and that of the traces for all loci examined. Due to the fact that also other relatives of the husband's male lineage lived in the same house, it was not possible to identify the man who really contributed to the traces. Therefore, the analysis was implemented with autosomal STR markers, which showed a mixed genetic profile. In order to verify the number and the identity of the contributors, statistical analysis based upon peak area information was performed with Probabilistic Expert Systems.