Fluorescent identification of biological and other stains on skin by the use of alternative light sources

The detection of body fluids in cases of sexual assault or abuse is important for purposes of evidence collection and DNA testing. In cases where semen is deposited on skin, a method for detection of semen may be a valuable aid to evidence collection [Gabby T, Winkleby M, Boyce T, Fisher D, Lancaster A, Sensabaugh G. Sexual abuse of children. The detection of semen on skin. AJCD 1992; 146:700-703]. Semen is known to fluoresce when exposed to light of certain wavelengths. For this study, we placed various body fluids, as well as lubricants and moisturizers on the forearms of volunteers. The areas were illuminated using Alternative Light Sources (ALS) with peak wavelengths of between 370 and 500 nm for examination soon after deposition, and again after 24 h. No fluorescence was visible from any of the substances in the majority of volunteers examined. In a few subjects, semen and urine were found to fluoresce faintly under the more powerful lights. In these cases, the quality of fluorescence provided by urine and semen was noticeably different. For comparison, semen was applied to cloth, and fluoresced well at the expected wavelengths. While ALS is useful for identification of stains on clothing, its use in detecting stains on skin is currently very limited.