The Survey of Frequency of Acid Phosphatase-Positive Results in Sexual Assault Cases Referred to Tehran Central Legal Medicine Office from January 2012 to January 2013

To prove the claim of sexual assault, the victim should prove its occurrence and declare any evidence confirming the assailant’s identity such as semen on the victim’s body, clothes, linen or any other belongings. Semen contains a high level of acid phosphatase, which can be used as a strong possible marker of semen. This study is conducted to survey the frequency of acid phosphatase positive results in sexual assault claimants who had come to Tehran Central Legal Medicine Office from January 2012 to January 2013. This study is a cross-sectional descriptive analytic survey on 352 female sexual assault claimants. We collected samples from those who had arrived within the first five days following the occurrence of the claimed assault (86 cases). We also took any suspicious semen-stained objects from the victims regardless of the time passed since the claimed assault. These samples were assessed for acid phosphatase and the results were analyzed by SPSS version 22 software. 352 sexual assault claimants were visited and 115 samples were taken from 86 cases. We got positive results from 27 percent of these samples. Also, 60 percent of 45 personal belongings, which had been delivered were acid phosphatase positive. Eighty percent of the positive vaginal samples and 100 percent of the positive anal samples belonged to victims who had been visited during the first 72 hours. Twelve percent of the positive vaginal cases belonged to those with intact hymen. Similarly there was no sign of anal injury in 44.4 percent of positive anal results. Although no acceptable correlation was found between positive results and the time passed since sexual assault, it seems the early hours after the event are the best time for examination of victims. Positive results can be expected only during the first 72 hours in anal assault and even beyond 72 hours in vaginal assaults. Furthermore, in case of existing ejaculation, evidences should be collected even when there is no sign of apparent anal or hymenal injury.