Hair: Microscopic Analysis

Abstract With some rare exceptions mammals possess hairs and mammals lose hairs! The “human” animal loses in the order of 100–150 scalp hairs each day. It is for this reason that hairs are almost certainly found at most crime scenes. Hairs of nonhuman and human origin are readily distinguishable and it is possible to describe their microscopic appearance. On the basis of these microscopic features, it is possible to compare animal hairs and to sometimes identify the type of animal from which the hairs originated. For human hairs, on the basis of their microscopic features, it is also possible to individualize hairs to some extent. Human hair varies within an individual and between individuals. The challenge for the forensic hair examiner is to capture this microscopic information and to use it to differentiate hairs from different sources. In this article, the rationale and science underpinning hair examinations is described. The role of microscopic examination and the other techniques such as DNA testing is considered. Finally, the value of hair as evidence and, how it may meet relevant evidence standards, is discussed.