Defense Date
2022
Document Type
Directed Research Project
First Advisor
Dr. Sarah-Seashols Williams
Second Advisor
Dr. Catherine Connon
Third Advisor
Kristin Van Itallie
Abstract
Sexual assault is currently one of the most prevalent crimes that affects victims of all ages. Forensic DNA analysts often confirm proof of contact in sexual assault cases through the identification of spermatozoa and subsequent STR profiling. Diapers and other feminine hygiene products, such as maxi pads and ultrathin pads, are types of superabsorbent polymer-containing evidence that complicate the process of DNA analysis due to the trapping of the spermatozoa in the gel-like matrix. In this study, a comparison of methods was performed to determine which extraction technique produces the highest sperm cell and DNA yield and generates a usable STR profile. When comparing the previously reported centrifugal filtration and calcium chloride (CaCl2) dehydration methods, a teasing and filtration method, and a sodium chloride (NaCl) and filtration method, microscopic examination demonstrated significantly different sperm yields using the sodium chloride method for the diaper samples and the teasing and filtration method for the remaining substrate types. However, when quantifying the DNA extracts obtained from the substrates, most methods resulted in similar DNA concentrations, with little indication of degradation or inhibition. All four extraction methods produced full STR profiles with no indication of inhibition or degradation. This suggests that forensic laboratories have the flexibility to choose among these spermatozoa extraction methods when analyzing superabsorbent polymer-containing evidence.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
5-7-2022