Prostatic acid phosphatase activity in the postcoital vagina

The present results are in general agreement with previous reports on the minimal level of AP activity that should be designated positive and on the period after intercourse in which elevated levels can be demonstrated. In this study 100% of the specimens above 25 KAu were taken within 48 hours of intercourse and 85.7% of these were within 24 hours. For values above 50 KAu, all were within 24 hours of intercourse. A low AP level does not rule out the possibility of recent coitus, particuarly if the woman was menstruating or had douched or used some suppository preparation. These findings also point to the possible interference of certain pathologies in correlating AP activity and time since coitus. As other authors have shown and this study has confirmed, some reactive substance seems to be present in the vagina at all times. For the use of AP assays in the forensic investigation of alleged rape cases, it is suggested that a thorough, accurate history be obtained with regard to douches and suppositories and that the presence of vaginal pathologies be noted. Further research on the techniques used in the forensic investigation of sexually related crimes is proceeding. The large proportion of negative samples within 24 hours of intercourse in this and other studies needs clarification. Other sampling techniques and the quantitative measurement of several different constituents of semen may offer accurate estimates of the time of last intercourse. Large studies with stringent control of the possible variables will further refine this important area of forensic science.