Forensic identification of a murderer by typing volunteers of a small village of Northern Italy

Abstract

In this paper, we report the real case of a murder, committed in a small village (about 1000 people) in Northern Italy, whose culprit was identified through the paternity test. The corpse of an elderly female (75 years old) was found in her house. The cause of death was determined to be a violent blow. There were also signs of sexual assault to the body. The investigators sent much evidence to our lab: it also included some stains, presumably consistent with semen, collected from the victim's pubic hair. Microscopic analysis of the semen residues permitted the identification of spermatozoa with tails attached; the subsequent DNA typing allowed us to obtain a complete male profile for 17 STRs. The investigators focused their attention on some men with criminal records of sexual crimes who were suspected of the murder, but they were all excluded by DNA profiling. However, the profiles we obtained from those people showed a characteristic similarity for many alleles/loci, due to possible inbreeding. Hence, we suggested to both the prosecutor and the investigators that the people ranging 18–65 years of age living in the village be invited to give a sample of their saliva. We received a total of 400 saliva samples, which underwent genetic analysis. All donors but one were excluded. Sample 47 in fact suggested a possible parentage linkage (father–child) with the murderer, showing at least one identical allele for any STR locus analysed, with the profile obtained from semen. Due to these results, the investigators took more information and established that the donor numbered as sample 47 had a 19-year-old son, who had not been typed because he was serving in the military. Immediately, the investigators collected and sent an oral swab of the suspect to our lab. Before the analytical results, he confessed to the crime: his DNA profiling was recognized as identical to that of the semen collected from victim. This is the first example in Italy of parental test used to identify a murderer. Moreover, this is the first report on DNA typing, of the entire population of a small Italian village used for crime investigation.