Microscopical discrimination of human head hairs sharing a mitochondrial haplogroup

DNA and protein analyses of hair in forensic genetics

Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.

Routine Mitogenome MPS Analysis from 1 and 5 mm of Rootless Human Hair

While hair shafts are a common evidence type in forensic cases, they are often excluded from DNA analysis due to their limited DNA quantity and quality. Mitochondrial (mt) DNA sequencing is the method of choice when working with rootless hair shaft fragments due to the elevated copy number of mtDNA and the highly degraded nature of nuclear (n) DNA. Using massively parallel sequencing (MPS) of the mitochondrial (mito) genome, we studied the impact of hair age (time since collection) and physical characteristics (hair diameter, medullary structure, and length of hair tested) on mtDNA recovery and MPS data quality. Hair shaft cuttings of 1 and 5 mm from hairs less than five years to 46 years of age from 60 donors were characterized microscopically. Mitogenome sequences were generated using the Promega PowerSeqTM Whole Mito System prototype kit and the Illumina MiSeq instrument. Reportable mitogenome sequences were obtained from all hairs up to 27 years of age (37 donors), with at least 98% of the mitogenome reported for more than 94% of the 74 hair samples analyzed; the minimum reported sequence was 88%. Furthermore, data from the 1 and 5 mm replicates gave concordant haplotypes. As expected, mtDNA yield decreased, mtDNA degradation increased, and mitogenome MPS data quality declined as the age of the hair increased. Hair diameter and medullary structure had minimal impact on yield and data quality. Our findings support that MPS is a robust and reliable method for routinely generating mitogenome sequences from 1 and 5 mm hair shaft samples up to 27 years of age, which is of interest to the forensic community, biological anthropologists, and medical geneticists.

Forensic hair analysis - Worldwide survey results

Forensic hair analysis remains under the microscope. Although hair evidence can yield information pertinent to an investigation, past issues with associated expert testimony endure. The aim of this survey was to gain a better understanding of hair analysts by expanding on past findings by assessing methodology, terminology and bias, analysing demographic and workplace data and allowing participants to comment on current and future issues in hair analysis. An online survey was designed and disseminated to hair analysts worldwide and 176 analysts from 12 countries took part in the survey. Participants responded to questions regarding accreditation, the probative value of hair evidence, collection and packaging, contextual information, methodology, terminology and reporting results, conclusions and opinions. The probative value of hair evidence was supported and other than selection of mounting medium the survey identified a preference of collection methods, packaging materials, use of microscopy and notetaking. Terminology used when conducting hair analysis and reporting results varied and caution towards statistics was expressed while training and collaboration was encouraged. The survey data will be used in the development of validation studies in hair analysis for future dissemination.