Differentiation of vaginal cells from epidermal cells using morphological and autofluorescence properties: Implications for sexual assault casework involving digital penetration

This work explores morphological and autofluorescence differences between vaginal and epidermal cells detectable through Imaging Flow Cytometry (IFC), a non-destructive, high-throughput technique. These differences were used to build a predictive framework for classifying unknown cells as originating from vaginal or epidermal tissue, which was tested on hand swabbings with and without digital penetration. Many more cells possessing a vaginal signature (median posterior probability ≥0.90) were detected in digital penetration samples than control hand swabbings. Minimum interpretation thresholds were developed to minimize/eliminate false positives; these thresholds were also effective when screening licked hands, indicating the potential utility of this method for a variety of biological mixture types and depositional events relevant to forensic casework.     

Can mRNA markers distinguish traces generated by different types of contact?

The presence of contact traces on objects can be caused by different activities such as personal use, firm gripping or casual touching. As these activities are of distinct duration and intensity, we hypothesised that cell material corresponding to different epidermal depth may be deposited. Epidermal layers have distinguishable biomarker profiles [1], [2] that are formed by cell proliferation, cell differentiation and cell death. Thus, we examined whether mRNAs corresponding to different epidermal layers can distinguish the different types of contact. From an initial set of 14 candidates, six epidermal markers showed sufficient expression in contact traces to be included in an mRNA multiplex assay that carried body fluid markers as well [3]. Using a set of 30 user and 30 grip traces left by identical donors on identical substrates, we determined that none of these epidermal mRNAs could specify contact type. When the corresponding DNA data were included in the analyses no relation with contact type could be established either.     

Species identification of some common necrophagous flies in Guangdong province, southern China based on the rDNA internal transcribed spacer 2 (ITS2)

Despite the fact that the differences in epidermal ridge density between men and women have been accepted for some time, they have only been thoroughly demonstrated in a small number of populations. The aim of this study is to determine whether such differences exist in a sample of the Spanish population by counting epidermal ridges within three well-defined fingerprint areas. If significant gender differences do exist, then the likelihood of inferring gender from given ridge densities will be explored. The data used in this study was obtained from all 10 fingerprints of 200 individuals of the Spanish Caucasian population (100 males and 100 females) between the ages of 20 and 30. Results show that women tend to have a significantly higher ridge density than men in the distal region of all 10 fingers (radial and ulnar count areas), but not in the proximal region (lower count area). The application of Bayes' theorem, assuming that prior probabilities known for each sex, indicate a threshold for discrimination of sexes.