Detection of male DNA in the vaginal cavity after digital penetration using Y-chromosome short tandem repeats.

In this study, useful genetic information from male donors was obtained on vaginal swabs taken from female volunteers after male digital vaginal penetration in a time frame relevant to a sexual assault investigation. Vaginal swabs were collected from eight volunteers at intervals of 1, 6, 12, 24, and 72 hours after digital vaginal penetration. DNA was extracted from collected swabs and subsequently genotyped using a commercially available Y-chromosome short tandem repeats (Y-STR) multiplex kit. Fifty-eight vaginal swabs were collected and analyzed in the study. Composite Y-STR profiles from all combined volunteers showed that 85% of all possible alleles were detected at the 1-hour interval, 77% of all possible alleles were detected at the 6-hour interval, 73% of all possible alleles were detected at the 12-hour interval, 66% of all possible alleles were detected at the 24-hour time interval, and 71% of all possible alleles were detected at 72 hours after digital vaginal penetration. Results indicate that a viable possibility exists that probative Y-STR profiles, useful for investigative purposes, can be obtained from vaginal swabs taken from subjects exposed to digital penetration at time intervals up to 72 hours postpenetration.