Y-str as Proof of Rape When Sperm Cells Cannot Be Found

Identification of spermatozoa is the biological evidence most often sought in the examination of rape victims. Absence of spermatozoa usually terminates biological investigations, and the victim’s testimony can therefore be contested. We assessed the utility and reliability of PCR amplification using Ychromosomal STR polymorphisms in specimens taken from female victims of sexual assault with negative cytology. Overall, when sperm cells could not be found, Y-chromosome STRs were detected and demonstrated sexual penetration in 28.8% of 104 swabs obtained from 79 victims. In the population of victims examined more than 48 hours after the sexual assault, Y-STR were still observable in 30% of cases. These results show that swabs can be taken from victims for Y-chromosome DNA typing even after a long lapse of time between the sexual assault and medical examination.