Detectability of seminal stains on fabrics after various washing steps

Background and aim s: Biological evidence that can help in individualization by DNA profiling is considered crucial evidence in a court of law and helps in the timely delivery of justice. In sexual assault cases, the evidence having the utmost importance is detecting semen in the genital swab or on the victim’s clothes. However, semen stains may be washed before seizure by investigating agencies, and some semen can remain as evidence even after washings. This study aims to find the most suitable methods for detecting semen stains after various washing steps. Material and methods: White cotton fabric pieces were stained uniformly with semen and air-dried for ten days. The stains were washed in two batches, i.e., with detergent and without detergent, for different time intervals. The screening, UV examination, acid phosphatase test, Florence microcrystal test, and Barberio microcrystal test were used. For the confirmation, a prostate-specific antigen (PSA) test and microscopic examination were used. Results: UV Examination gave positive results up to moderate wash, and acid-phosphatase gave a positive result in all washes when done with water only on the contrary with detergent, it gave result only in the soft wash. In the confirmatory test, the PSA Test showed high sensitivity showed positive results in all washings, whereas in the microscopic examination, sperms/ sperm heads could be detected in all washed stains, but with detergent the presence of sperm was limited up to the soft wash only. Conclusion: Washings of semen-stained fabrics with detergent significantly reduced the possibility of detecting semen and sperms for almost all tests conducted, compared to fabrics washed without detergent. PSA test showed distinguishable results even after several steps of washings. Thus the test of choice for the detection of semen on washed fabrics is PSA.