Y-STR analysis for detection and objective confirmation of child sexual abuse

We evaluated 26 child sexual assault cases for the incorporation of Y-STR screening in the routine detection and objective confirmation of sexual contact between the child victim and the perpetrator. Various samples, e.g. vaginal or anal swabs from patients aged 2-17 years old (25 females, 1 male), were collected 6-72 h after the incident. Due to the limited amounts of DNA in these samples, total DNA was extracted using a one-step procedure and screened with autosomal STRs to detect signs of a victim-assailant DNA mixture and with Y-STRs for assailant DNA. Autosomal STRs failed to give signs of victim-assailant DNA mixtures while Y-STRs were detected in 24 of the 26 cases corresponding to a success rate of 92.3%. With the possible presence of both male sperm and/or male epithelial cells in forensic evidence, Y-STR DNA markers were detected regardless of external ejaculation, microscopic detection of sperm and with post-coital intervals of up to 72 h. While only partial profiles were generated owing to low quantities of male DNA present, Y-STR screening results can serve as objective evidence of sexual contact in child sexual abuse cases involving victims who do not have any previous sexual history. This type of evidence can corroborate child victim testimony and spare the child victim from further trauma caused by prolonged forensic investigations and court proceedings. Alternatively, Y-STR screening can provide objective proof of non-involvement of an accused with the victim.