Forensic Analysis of Physical Disruption of Human Hair after being Treated with Henna and Dyes

Abstract

People are going through a lot of cosmetic treatments nowadays. The purpose of certain chemical treatments, such as henna and dye applications, is to improve the colour, texture, and other characteristics of hair. When conducting forensic investigations, hair analysis under a microscope and scanning electron microscopy can provide unique insights into trace evidence (hair) that may be retrieved from crime scenes. The non-permanent hair treatments that are applied are henna and dyes. Henna alters the colour and texture of hair by covering the cuticle when applied to individual hair strands. On the other hand, the dye not only penetrates the hair's cortex but also coats the cuticle, changing the structure and colour of the hair. The motive of this particular study was to examine the effects of henna and dyes on hairs within a 20-day period by microscopic inspection of the hair that has been treated with both. Under a phase-contrast microscope, hair samples treated with various brands of henna (namely, Brand H1, H2, and H3) were examined to show changes in the hair's structure, colour, and scale pattern. Under a microscope and scanning electron microscope, hair samples treated with various hues (black, brown, and burgundy) and brands (Brand D1, D2, and D3) were examined. The results showed changes in the colour, texture, and scale patterns of the individual hair strands. Compared to hair treated with henna, dyed hair had higher damage. Additionally, the degree of damage varies based on the brands and colour used. This study can give an investigator a starting point for reducing the number of suspects who have had their hair dyed or hennaed.