Improving the detection of spermatozoa microscopically from routine sexual assault examinations

Abstract

ABSTRACT This study determined that the detection of spermatozoa could be improved by submitting sexual assault swabs directly for Differential Lysis extraction, whilst preserving the ability to conduct presumptive testing, eliminating the need to prepare a microscopic slide during initial examination. Analysis of semen from cotton swabs, rayon swabs, scrapings, tape-lifting and excisions from both thick and thin fabrics was conducted to ensure that the methodologies evaluated were tested on a range of exhibits and biological fluids typically seen in routine forensic casework. Results showed that microscopy slides created during Differential Lysis Extraction performed favourably in comparison with slides created during initial examination. A newly developed sexual assault process gave comparable detection levels to the traditional processing for Prostate Specific Antigen (p30) and Phadebas presumptive testing. It should be noted that the detection sensitivity for Acid Phosphatase (AP) was slightly better for traditional processing. The sensitivity of p30 was shown to be far superior to that of AP across most experiments.