Quantitation of vaginal acid phosphatase and its relationship to time of coitus.

In cases of alleged sexual assault a quantitative vaginal acid phosphatase determination may indicate not only the presence of seminal fluid but also the approximate time of coitus, even in the absence of spermatozoa. A method of obtaining and handling vaginal swabs allowing for acid phosphatase determination and examination for spermatozoa was developed. Postcoital samples were obtained from 26 women and analyzed for ACP activity. Quantitative levels of ACP were related to time since coitus. These levels were compared with those found in 104 cases of alleged sexual assault and in 27 women volunteers.