To address various identified challenges, we investigated a new approach for characterizing trace evidence prior to DNA profiling that labels epidermal cells with antibody probes targeting hormone molecules testosterone and dihydrotestosterone (DHT), with the goal being to test whether cell populations derived from separate individuals showed different binding efficiencies to hormone probes and, thus, could be used to detect the presence of multiple cell populations.
Additionally, we investigated whether antibody probes could be used to isolate contributor cell populations from an epidermal cell mixture and facilitate deconvolution of mixed DNA profiles recovered from touch/trace evidence. Results showed that cell populations from some individuals could differentiated in trace samples based on fluorescence histograms following probe labeling. However, certain pairs of contributors showed largely or completely overlapping histogram profiles and could not be resolved. Preliminary efforts to separate cell populations that could be differentiated with hormone probes with fluorescence-activated cell sorting (FACS) coupled to DNA profiling and probabilistic modeling indicated that it is possible to enrich contributor cell populations from touch/trace samples and produce more probative DNA profiles compared to the original mixture sample. The variability in labeling, differentiation, and physical separation of cell populations may be impacted by similarities in biochemical profiles across some contributors as well as imbalance of contributor DNA quantities in certain mixtures as is typical in casework involving touch/trace evidence. Ultimately, screening and separation of trace DNA samples with this approach may be presumptive and constrained by sample-specific parameters of the original mixture. (Publisher abstract modified)
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