Use of prostate specific antigen in the identification of semen in postmortem cases

Over the past 20 years, the use of prostate specific antigen (PSA) as evidence of the presence of semen in forensic cases has been well established. In this study, we compared a commercially available immunoradiometric assay (IRMA) for the identification of PSA with the identification of spermatozoa in swabs obtained from the vagina of deceased females. There was agreement between the 2 methods in 67 of the 80 cases (84%), including 18 cases where both the PSA was positive and sperm were observed microscopically. The remaining cases had 1 positive result and 1 negative result. We concluded that although there was substantial agreement between the presence of sperm and a positive PSA, there were enough discrepancies between the 2 methods (16%) to justify the use of both methodologies, if possible, to make the determination of sexual activity prior to death.