Improving the detection of spermatozoa microscopically from routine sexual assault examinations

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.

KEYWORDS:

• Spermatozoa
• differential lysis extraction
• microscopy
• semen
• acid phosphatase
• prostate specific antigen

Acknowledgments

The authors wish to acknowledge all QHFSS staff who completed laboratory work for this project. Special acknowledgments to Abigail Ryan, Anita Sandanasamy, Michelle Margetts and Nicole Roselt for their extensive assistance with preparing and/or conducting experimental work, and to the donors of the biological material provided for testing.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Internally funded by Queensland Health Forensic and Scientific Services – Forensic DNA Analysis Department