Body Fluid Identification in Samples Collected after Intimate and Social Contact: A Comparison of Two mRNA Profiling Methods and the Additional Information Gained by cSNP Genotypes

The ability to associate a contributor with a specific body fluid in a crime stain can aid casework investigation. The detection of body fluids combined with DNA analyses may supply essential information, but as the two tests are independent, they may not be associated. Recently, the analysis of coding region SNPs (cSNPs) within the RNA transcript has been proven to be a promising method to face this challenge. In this study, we performed targeted RNA sequencing of 158 samples (boxershorts, fingernail swabs and penile swabs) collected from 12 couples at different time points post-intimate contact and after non-intimate contact, using the Ion S5™ System and BFID-cSNP-6F assay. The aim of the study was to compare the performance of the MPS and CE methods in the detection of mRNA markers, and to associate body fluids with contributors by their cSNP genotypes. The results of the study show a lower success rate in the detection of vaginal mucosa by the MPS compared to the CE method. However, the additional information obtained with the cSNP genotypes could successfully associate body fluids with contributors in most cases.