Rapid Stain Identification (RSID-TMSemen): A rapid tool for seminal fluid detection

Abstract

Introduction: The identification of semen stain is one of the most common human stains that can provide crucial information for crime scene reconstruction and forensic investigation. In sexual assault cases semen identification helps to support or refute victim’s allegations, it also provides a material for DNA analysis. The rapid Stain Identification of Human Semen (RSIDTM -Semen) bioassay is designed to detect specifically the presence of human semenogelin. It does not cross‐ react with other human or nonhuman tissues. Aim: To assess the efficacy of RSIDTM – Semen strip test for the detection of human semen under some different variables (different fabrics, different time intervals and mixed with vaginal secretions). Methodology: Semen samples were collected from four male participants; each sample was divided into two portions; one used for semen only test group and the other mixed with vaginal secretions for the mixed test group. Vaginal swabs were carried out from the four female participants using cotton, linen or nylon-tipped plastic rods (2 swabs from each female). One of the fabrics tipped vaginal swab was mixed with semen for the mixed test group and the other used as a positive control group to test the sensitivity and specificity of the RSIDTM – Semen strip. The semen samples were deposited over different fabrics at the same time. All the samples were left to dry for 15 minutes at room temperature (summer) then extracted and analyzed. Each of the previous groups, was categorized into 5 subgroups (a, b, c, d and e) according to the time interval of semen extraction (zero (on the spot), 2, 4, 6 and 10 days respectively). Results: Semen could be identified in 100% of tested samples of the semen only group as well as of the combined semen and vaginal secretions group over cotton and linen fabrics at all the different tested time intervals. However, semen extracted from nylon fabric was identified in tested samples of the semen only group and of the combined semen and vaginal secretions group only at zero time only and couldn’t be identified at the rest of tested time intervals. Conclusion: The current study evidenced that the new RSIDTM -semen kit is a reliable method for semen identification over different types of fabrics even in the presence of vaginal secretions. It also persists up to 10 days except on nylon fabric.