Defense Date

2024

Document Type

Directed Research Project

First Advisor

Christopher J. Ehrhardt

Second Advisor

Sarah Seashols-Williams

Third Advisor

Amanda Elswick Gentry

Abstract

Touch DNA samples are commonly found in the crime scenes. However, the presence and abundance of different biological components within these samples can result in varying DNA yields and impact the quality of the resulting DNA profile. This study developed morphological and autofluorescence signatures for differentiating non-nucleated epidermal cells from nucleated epithelial cells in trace biological samples using flow cytometry. Reference saliva and reference hand epidermal samples were used for signature development followed by testing with mock mixture samples containing both cell types. The results showed that hand epidermal cells have overall smaller sizes and higher autofluorescence intensities (at emission wavelengths of 523/30 nm, 583/26 nm, and 695/50 nm) compared to saliva cells. For experiments with mock mixtures, each sample was split into two subsamples with one analyzed by flow cytometry and the remaining subsample subjected to standard DNA profiling. Flow cytometry results from mixture samples showed evidence of tissue-specific signatures for hand and saliva cells. and that saliva can be successfully detected in varying quantities when in a mixture with touch epidermal cells. Further, DNA profiling of these samples indicated that mixture samples with saliva cell signatures often had higher DNA yields and profiles that were either single source or had a clear major contributor corresponding to the saliva donor.

Rights

© The Author(s)

Is Part Of

VCU Master of Science in Forensic Science Directed Research Projects

Date of Submission

5-2-2024

Available for download on Tuesday, May 01, 2029

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