Defense Date
2024
Document Type
Directed Research Project
First Advisor
Dr Christopher Ehrhardt
Second Advisor
Dr Sarah Seashols-Williams
Third Advisor
Dr Julie Burrill
Fourth Advisor
Kate Philpott
Abstract
One of the most challenging types of assault cases encountered by forensic laboratories involves groping, fondling and strangulation, where the focus is biological material left behind on the skin of the victim from hand contact that deposits fluids such as sweat and/or epidermal cells. Although DNA profiling can be utilized, this will only speak to whose biological material is present and will not indicate how the DNA was deposited. In cases where the alleged suspect lives with the victim, there can be several alternative hypotheses for the presence of DNA that involve cells transferring from sources other than the alleged suspect’s hands and therefore will be categorized as unrelated to the assault. Therefore, there is a need for methods that can differentiate epidermal cell populations originating from the hand from cells originating from other areas of the body. One such promising approach is to use Imaging Flow Cytometry (IFC) on the front end of the DNA workflow. Imaging flow cytometry is a rapid, non-destructive, and high-throughput method that can be used to characterize cells based on their physical attributes and autofluorescence profiles. The aims of this study were to (1) develop a signature capable of distinguishing between epidermal cells from the hand and epidermal cells from the neck using flow cytometry-based signatures (2) test whether the presence and/or abundance of each cell type in a mock mixture can be used to support activity propositions in cases involving strangulation. Cell signatures were characterized using IFC, followed by image analysis and blinded classifications using Linear Discriminant Analysis.
Results showed that the hand epidermal cells could be successfully differentiated from epidermal cells derived from an individual’s neck with high accuracy (>95%). Results from eight epidermal mixture samples suggest that hand epidermal cells can be deposited onto the neck surface through physical contact and subsequently detected with this workflow, with an accuracy of >83%. However, it was also noted that hand epidermal cells were not detected in all eight mixture samples, with clear evidence of the presence of hand cells in only three out of the eight mixtures analyzed. However, the results from this study demonstrate that hand epidermal cell populations can successfully be distinguished from cell populations originating from the neck. With further research, this method has the potential to be utilized as a front-end analysis technique prior to DNA analysis, provide probative context for assault cases, and aid in resolving questions that may come up when biological evidence is presented in court.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
4-30-2024