Assessing Single-Source Reproducibility of Human Head Hair Peptide Profiling from Different Regions of the Scalp

Abstract

Neither microscopical hair comparisons nor mitochondrial DNA sequencing alone, or together, constitutes a basis for personal identification. Due to these limitations, a complementary technique to compare questioned and known hair shafts was investigated. Recently, scientists from Lawrence Livermore National Laboratory's Forensic Science Center and other collaborators developed a peptide profiling technique, which can infer nonsynonymous single nucleotide polymorphisms (SNPs) preserved in hair shaft proteins as single amino acid polymorphisms (SAPs). In this study, peptide profiling was evaluated to determine if it can meet forensic expectations when samples are in limited quantities with the possibility that hair samples collected from different areas of a single donor's scalp (i.e., single source) might not exhibit the same SAP profile. The average dissimilarity, percent differences in SAP profiles within each source, ranged from 0% difference to 29%. This pilot study suggests that more work is needed before peptide profiling of hair can be considered for forensic comparisons.

Forensic proteomics

“…This will mirror the work conducted on proteomic body fluid determination [224,232,[234][235][236]239]. Cross-laboratory studies have been conducted, although the field is yet to consolidate around a single mass spectrometry platform [142,293]. This would help to establish standardization, guidelines for interpretation, and appropriate levels of consistency, reproducibility, robustness, sensitivity and discriminatory power.…”

“…The method would need to pass hearings, in a Daubert, Frye or Kelly context, on the legal applicability of evidence obtained. These have strict and well-established guidelines, SWGDAM requires a thorough analysis of the replicability, reproducibility, sensitivity, detection limits and whether the human GVPs also occur in other species [222,286,290,293]. These will start to accumulate as the priorities of the field move from increasing sensitivity and maximizing detection, a binary outcome, to a more quantitative approach that incorporates limits of detection and quantitation.…”

Recent advances in forensic biology and forensic DNA typing: INTERPOL review 2019–2022

“…A thorough review of forensic proteomics in 2021 cited 375 references [ 18 ]. Recent efforts in this area have focused on using GVPs to differentiate individuals through their human skin cells [ [548] , [549] , [550] ] or hair samples [ [551] , [552] , [553] , [554] , [555] , [556] , [557] , [558] , [559] ]. An algorithm has been proposed for calculating random match probabilities with GVP information [ 560 ].…”