Proteins in biological evidence provide material for human identification when DNA is absent or compromised and can augment DNA evidence when it is present. Analysis of protein sequences reveals amino acid substitutions that can be used as identity markers. Peptides containing these amino acid substitutions are known as genetically variant peptides (GVPs). A key aspect of using GVPs in a forensic context is their link to associated SNPs in the DNA that code the corresponding proteins. As a result, SNP population frequencies can be used to calculate statistics such as random match probability derived from protein evidence and rules of genetic inheritance can be used to predict GVPs within family groups. Results of a recent project exploiting GVPs for human identification will be discussed. Hair and DNA samples were collected from subjects, which included father-mother-offspring “triads” in some cases. Exomic DNA was sequenced and used to predict the presence of rare SNPs and corresponding rare GVPs. Proteomic analysis of the hair samples guided by predictions from the exomic analysis was performed to locate these GVPs. The power of collections of both common and rare GVPs for individual identification in single and mixed (multiple-contributor) samples and the prediction of rare GVPs for an individual based on the DNA of related individuals will be shown. Advances in sample preparation of single hairs and extension of protein-based identification to skin cells from touch evidence will also be presented.

Human identification using genetically variant peptides in hair

256th National Meeting (2018)

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