[Identification of semen in bloodstains with the use of alternative light source and biochemical screening tests]

The objective of the investigation was the verification of the presence of semen in stains constituting mixtures of semen and blood employing alternative light source (ALS) and commercially available biochemical screening tests based on the activity of acid phosphatase (AP) and prostate-specific antigen (PSA). The tests demonstrated that discrimination between particular components of a blood-semen mixture was impossible either with the naked eye, as well as with the use of ALS. White fluorescence was observed only in stains consisting of pure semen and semen-blood mixtures at a ratio of 100:1. The assay for PSA was positive in the case of all the examined semen dilutions and semen-blood mixtures, whereas the sensitivity of the AP-based test assay was lower by one order of magnitude.