An international survey into the analysis and interpretation of microscopic hair evidence by forensic hair examiners

Due to inadequacies in historical hair examinations, the use and perceived value of microscopic hair evidence has reduced. Many reports have heavily criticised the use of pattern-based evidence including hair evidence as being unreliable, with police forces focussing on more individualising evidence. Hair evidence has been utilised in casework for many years due to its ability to transfer easily between individuals and crime scenes. Hair evidence can provide important information in criminal investigations, and in certain circumstances, aid in the identification of an individual, along with providing information to aid in the reconstruction of a crime scene. It has become apparent in recent studies, such as the 2012 FBI review, that hair evidence has been inappropriately utilised in case work and this, along with a preference for more discriminating methods such as DNA profiling, has led to both a lack of confidence in and reduction of use of hair evidence. The need for more standardised and objective methods is required along with improved methods for interpreting hair evidence. Since these reports, there has been no study investigating how these have affected the perceptions of hair evidence by forensic hair examiners or that has investigated what methods are being utilised to create a robust, objective and reliable interpretation of this evidence. This study aimed to assess the current similarities and differences in microscopic hair examinations and perceptions of its evidential value between countries, with a focus on the analysis and interpretation methods used by case work examiners and researchers.

This study will discuss the findings of a survey and interviews completed by hair examiners. Previous surveys have been conducted by Aitken & Robertson (1986) and Murphy (2013), however the current international status of microscopic hair examinations is unknown.

This study gathered responses across 9 countries. From this, it was identified that the microscopic examination of hair evidence is still valued highly by those practicing it. The amount of cases that an examiner has worked on that involve the examination of microscopic hair evidence is correlated to the perceived evidential value of hair evidence and to the value of morphological characteristics of hair. There are inconsistencies between the approaches used in interpreting this type of evidence. Subsequently, this study has generated an international understanding of the current status of hair examinations which was not previously known from an operational perspective.