Verification of the persistence of sperm traces under different chain-of-custody conditions. Care pathway and justice for victims of sexual violence and abuse

The primary aim of this study was to verify the persistence of seminal traces under varying chain-of-custody conditions, along with determining how different contamination factors, time intervals between collection, and storage methods influence the detectability of semen in the context of sexual assault cases. This study combined laboratory and field analyses to simulate real-case scenarios. Three forensic detection tools-Sperm Tracker Lab, Sperm Tracker Spray, and RSID™ tests-were evaluated on multiple substrates (skin, hair, nylon, cotton, and car interiors) and under various contamination conditions, including the presence of blood, dust, soil, and bodily fluids. Detection techniques included contact-pressure methods (Sperm Tracker Lab), application on uneven surfaces (Sperm Tracker Spray), fluorescence-based searches with ALS (alternative light sources), and immunochromatographic testing (RSID™ kits) for sperm-specific proteins. Positive findings were confirmed via microscopic examination and DNA analysis. All the samples were labelled and stored following strict chain-of-custody protocols. Sperm Tracker Spray demonstrated consistent effectiveness, successfully detecting minimal volumes (1-2 µL) across a wide range of materials. Conversely, ALS showed reduced sensitivity, especially in the presence of diluted or minimal traces and on textured or dark fabrics. RSID™ kits provided reliable confirmation of the presence of semen, even when environmental or biological contamination was present. Accurate and thorough documentation of the chain of custody proved essential for preserving sample authenticity and reducing the risk of error. The findings underscore the importance of a multidisciplinary forensic approach combining specialized reagents, confirmatory immunochromatographic testing, and rigorous adherence to chain-of-custody procedures. This integrated strategy enhances the reliability of seminal trace detection in investigations of sexual assault. Moreover, verifying trace persistence under diverse conditions contributes significantly to the evidentiary value of forensic samples in judicial contexts.