Variation between laboratory procedures for the microscopic examination of human hair

Abstract

A critical overview of forensic science was performed by the National Academy of Sciences (NAS) in 2009 which resulted in several recommendations for the advancement of the hair analysis discipline within the field of trace evidence examination. Among them included improvements to training and proficiency testing requirements, adaptation of uniform protocols between all laboratories, and enhanced research and development efforts aimed at reducing the subjectivity between multiple analysts or within the same analyst. A survey was created for forensic hair analysts to determine what current microscopic hair examination procedures are being used and to identify variability between characteristics of individual examiners and laboratory practices in the field, three years following the NAS report. The survey was completed by 117 members of the American Society of Trace Evidence Examiners (ASTEE) and contained questions about the experience and training of the analyst, impact of the NAS report findings, type of hair examinations performed, and hair features referenced during microscopic hair comparisons. Most analysts surveyed received the same substantial amount of training and have several years of experience; however, very few reported that any laboratory procedures were affected as a result of the NAS report. Though hair analysis is not structured by mandated, uniform standard operating procedures, largely the same number and type of hair features are being referenced when microscopic hair comparisons are performed, indicating that little variability exists between laboratories or individual examiners. A trend toward more frequent root screenings for DNA viability and less frequent full microscopic hair comparisons was detected and supplemented by a shift of hair analysis from trace evidence sections to biology or DNA sections. Several technologies new to forensic hair analysis are currently being explored to supplement hair analyses with numerical data and, therefore, reduce subjectivity of forensic hair analysis.