Taxonomic Source Identification of Hair

Hair fibers are a common form of biological trace evidence. Taxonomic classification can provide valuable forensic intelligence and aid in evidence prioritization. Traditional methods of classification, based on hair morphology, require expert interpretation, offer limited taxonomic resolution, and are not easily scalable. Mass-spectrometry-based proteomics provides a biomolecular alternative through taxon-specific amino acid polymorphisms to resolve species identification. In this study, a proteomics workflow was developed for the discovery and characterization of taxonomically diagnostic hair peptides in humans and 14 additional species, selected based on relevance to crime scene investigation. A panel of 226 taxonomically informative peptides were identified, with 207 novel to this study. This included 59 peptides with single-species resolution, while the remainder were diagnostic due to restricted taxonomic distribution or convergent evolution. The panel of taxa-discriminating markers was subsequently integrated into a forensic workflow. The developed workflow was used to analyze single fur-hair (20 mm), from four individuals from each species of interest. The data were processed using a curated hair protein database, providing an efficient bioinformatics workflow that did not require prior source information for identification. The method was able to classify all hairs analyzed with genus- or species-level resolution.