Hair analysis and hair fibre analysis are widely used in forensic sciences and in crime labs to aid in the identification and conviction of suspects. Human hairs can be transferred with contact and are the most common form of biological evidence left at a crime scene.
The collection of hair and hair fibre from a crime scene is a tedious procedure requiring tweezers and a magnifying glass or microscope.
Hair fibres are then analysed under a microscope to identify colour, texture, shape pattern, twist, and cross-sectional appearance, as well as any other identifiable surface characteristics.
Microscopic analysis of hair fibres can often determine the race of a suspect. It can also determine where on the body the hair was from, which has significance at a crime scene. Although sex cannot currently be determined from hair, advances in genetic research may make this a routine forensic technique.
Tests on the chemical composition of hair are often performed, testing for properties such as melting point, density, ash formation, tensile strength, and solubility. However, these tests destroy the hair and can only be performed once.
The root of hair is examined to determine how the hair was lost from the body. If the root is shown to have follicular tissue attached, forensic scientists know the hair has been forcibly removed.