BASIS FOR FORENSIC EXAMINATION OF HUMAN HAIR

• Jurisdiction: Australia

Introduction ................................................................................................... [88B.500]

Underlying principles and protocols.............................................................. [88B.520]

Hair colour..................................................................................................... 88B.540

[88B.500] Introduction

It is beyond the scope of this chapter to cover the detailed microscopy of human hairs. The purpose here is limited to:

• discussing the underlying principles and approach to hair examination in the context of the management of a case involving hairs;
• providing an introduction to the classes of microscopic features examined; and
• considering the evidential value of hairs and the interpretation of hair evidence.

[88B.520] Underlying principles and protocols

At the outset, it is important to emphasise that hairs will rarely be the only form of forensic evidence in a case. While it has become common practice for a multitude of experts to present their findings on individual categories of evidence, hair is at its most valuable when considered in the context of other biological and physical evidence.

All possible materials of potential evidential value should be recovered. However, provided items/exhibits are managed in an appropriate way, it may be possible to adopt a triage approach to analysis. For example, as far as possible, hairs should always be collected and retained. If the major issue in a case is one of the identity of an offender, then other sources of biological material may yield quicker and better results. Hairs should be considered as a secondary, but important, source for DNA analysis. Since DNA analysis was first used for forensic purposes in the late 1980s, its sensitivity has increased to the point where a DNA profile can be obtained even where there is little or no visible biological material. For the first 10 or more years of DNA application, it was only possible to obtain a profile from visible biological material such as a bloodstain or semen. This meant that there was at least a putative evidence link between the biological material and the alleged crime or event. With no visible and identifiable biological material, it is difficult, if not impossible, to say when the biological source of DNA was deposited which will often limit its potential evidential value. Furthermore, there may be mixed biological material from more than one donor resulting in a mixed DNA profile, further complicating interpretation.

The benefit and strength of hairs is that they are a recognisable physical and visible biological source. The location of hairs, and the nature and condition of hairs, may in themselves add to their evidential value. If the issues in a case go beyond identity to the "what happened", hairs may assist in answering this question. Here, the location and type of recovered hair may be of vital interest in showing the recovered material had not been left as a result of some innocent explanation. There are of...