Sophie Dessaux1, Emmanuelle Briant-Gicquel1, Myriam Siffointe1, Laurent Bartholin2, Claude Descorme1, Emilie Borges1*
Alternative-light sources (ALS) are widely used in both forensic laboratories and crime scenes for semen detection. This non-specific strategy is effective despite a few limitations, leading to both false negative and false positive results. To detect semen stains, specific acid-phosphatase (AP) tests can also be implemented in a controlled laboratory environment. However, they are not appropriate for direct crime scene investigations. A newly commercialized product could overcome all those limitations: Sperm Tracker (STK) Spray®, an AP-spray test for non-textile items.
In this study, we assessed its specificity, sensitivity, and compared its effectiveness with those of two well-known ALS on a wide range of materials, focusing on 32 different surfaces that can be commonly encountered on crime scenes. We found STK spray® easy to use, with a rapid fluorescent signal appearing in the presence of semen. It is specific, detects pure semen spots down to 1 μL and semen dilutions down to 1/20. Results showed that the fluorescent signal may be blocked by feces or blood but not by any of the other body fluids we tested. Comparison with ALS showed encouraging results, particularly on diluted semen stains for which ALS were less sensitive. This new reagent does not interfere with the Christmas tree spermatozoa staining method or with the process leading to DNA profiling.
In conclusion, the present study showed convincing results regarding the new STK spray® reagent and its further direct use on real crime scenes.
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