DOI
https://doi.org/10.25772/2cr2-ge64
Defense Date
2020
Document Type
Directed Research Project
First Advisor
Dr. Christopher Ehrhardt
Second Advisor
Dr. Susan Greenspoon
Third Advisor
Dr. Catherine Connon
Fourth Advisor
Kate Philpott, JD
Fifth Advisor
Dr. Sarah Seashols-Williams
Abstract
Current methods for confirming the presence of spermatozoa in sexual assault samples can be time-consuming and often lack sensitivity; however, this remains the most definitive test for the presence of semen. Additionally, male DNA can be deposited without the presence of intact sperm as may be the case with seminal fluid from vasectomized individuals or sexual activity where seminal fluid is not recovered (e.g., perpetrator wears a condom, penetration without ejaculation, etc.). The ability to detect bodily fluids, as well as quantify their presence in a sample, could aid in forensic DNA analysis by limiting the amount of time performing serological testing, as well as screening for probative samples for DNA profiling. Additionally, determining the cellular makeup of a sample can be informative for investigative purposes, e.g. rebutting or supporting certain factual claims from the victim or defendant. Morphological and/or autofluorescence cellular signatures are rapid and non-destructive methods for cell type differentiation in the clinical context but have not been thoroughly explored for forensic casework applications. Therefore, the goal of this study was to characterize signatures in four major cell types associated with sexual assault casework (vaginal, rectal, and penile epidermal cells, and azoospermic seminal fluid) towards the development of a method for rapidly identifying and/or differentiating these cell/fluid types in biological evidence. Morphological and autofluorescence profiles of each cell population were analyzed with Imaging Flow Cytometry (IFC) using five different excitation wavelengths and six detector channels ranging between 430nm-780nm. Signatures for each cell type were constructed from ~60 different individual cell measurements. Finally, linear discriminant analysis was used to develop a quantitative framework for differentiating cell populations and predicting cell types. Vaginal, rectal, and penile cells can be differentiated with a high degree of accuracy, ~90%. This framework was also highly accurate at differentiation semen (including azoospermic and proteinase K treated semen) from vaginal and rectal cell populations. However, there were still many factors that contributed to these levels of accuracy including, but not limited to, inter-donor variability. Ultimately, the results obtained indicate that each cell type have distinctive signatures that can be detected in a rapid and non-destructive manner.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
11-24-2020