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Postcoital detection of a male-specific semen protein. Application to the investigation of rape
Abstract:
Identification of semen in vaginal fluid may provide documentation of sexual contact in alleged victims of rape. We describe an enzyme-linked immunosorbent assay for a semen glycoprotein of prostatic origin, designated p30. This test detects as little as 3 ng of the p30 antigen per milliliter in various body fluids. Semen from normal and vasectomized men contains high levels of p30 (mean, 1.55 mg per milliliter of seminal plasma), and urine from men contains low levels (mean, 260 ng per milliliter). However, the antigen cannot be detected in body fluids from women, including vaginal fluid and urine, suggesting that p30 may be a male-specific antigen. The p30 antigen was detectable in vaginal fluid for a mean period of 27 hours after coitus, as compared with 14 hours for prostatic acid phosphatase. Of 27 vaginal fluid samples from women who were allegedly raped in which the acid phosphatase test was negative, 7 (26 per cent) were unequivocally positive for p30 by our assay. We conclude that the assay for p30 offers a more sensitive and specific method of semen detection in rape investigation than the enzyme assay for prostatic acid phosphatase.
Insights
A new assay for p30, a semen glycoprotein, offers a more sensitive method for detecting semen in alleged sexual assault cases. This test identifies semen for longer periods than traditional methods, improving evidence collection in rape investigations.
Area of Science:
- Forensic Science
- Biochemistry
- Immunology
Background:
- Documentation of sexual contact is crucial in alleged rape cases.
- Current methods for semen detection may lack sensitivity and specificity.
Purpose of the Study:
- To describe a novel enzyme-linked immunosorbent assay (ELISA) for detecting p30, a semen glycoprotein.
- To evaluate the efficacy of the p30 assay in forensic samples.
Main Methods:
- Development of an ELISA for the p30 antigen.
- Quantification of p30 levels in various body fluids from men and women.
- Comparison of p30 detection duration in vaginal fluid post-coitus with prostatic acid phosphatase.
Main Results:
- The p30 assay detects as little as 3 ng/mL of the antigen.
- p30 is present in high concentrations in semen and low concentrations in male urine, but undetectable in female body fluids, suggesting male specificity.
- p30 was detectable in vaginal fluid for a mean of 27 hours post-coitus, compared to 14 hours for prostatic acid phosphatase.
- 26% of vaginal fluid samples negative for acid phosphatase were positive for p30.
Conclusions:
- The p30 assay is a sensitive and specific method for semen detection.
- This assay offers improved forensic capabilities in rape investigations compared to prostatic acid phosphatase testing.