Which marker can unequivocally identify the presence of semen when positive?

Which marker can unequivocally identify the presence of semen when positive?

• A. A positive PSA test can unequivocally identify the presence of semen.
• B. PSA indicates sperm motility.
• C. PSA confirms blood type.
• D. PSA detects saliva.

Answer: (A)

Prostate-specific antigen (PSA) is a protein made by the prostate and released in semen. Because semen contains high levels of PSA, a positive PSA result in a stain or sample is a strong, highly specific indicator that semen was present. The other statements miss what PSA tells you: PSA doesn’t measure sperm motility, it isn’t used to confirm blood type, and it isn’t a marker for saliva. In typical forensic samples, a positive PSA test is the best evidence among the options that semen was present, even though no test is perfect in every situation.

Prostate-specific antigen (PSA) is a protein made by the prostate and released in semen. Because semen contains high levels of PSA, a positive PSA result in a stain or sample is a strong, highly specific indicator that semen was present. The other statements miss what PSA tells you: PSA doesn’t measure sperm motility, it isn’t used to confirm blood type, and it isn’t a marker for saliva. In typical forensic samples, a positive PSA test is the best evidence among the options that semen was present, even though no test is perfect in every situation.