Forensic scientist taking a hair specimen for DNA testing from clothing from a crime scene.Credit: Tek Image/SPL /Getty Images
The accuracy of human hair analysis could be improved with the routine addition of body hair screening.
A study published in the International Journal of Molecular Science sought to assess the potential benefits of a multidimensional approach to differentiating body hairs. This included whether scalp hairs could be substituted with body hairs, which have been generally neglected in forensic studies.
Hair is well suited to forensic analysis. Its high keratin content makes it resistant to decay and, depending on its length, hair is also a reliable barometer of historical exposure to foreign chemical substances in the body. Analysis can be affected by the impacts of ultraviolet degradation and cosmetic treatments on scalp samples.
“Our study found that body hairs differ in their physico-chemical profile, and so would provide variable data when testing for chemical compounds such as drugs,” said lead author Karen Cloete, a senior researcher affiliated to the UNESCO-UNISA Africa Chair in Nanosciences & Nanotechnology.
The differences between the molecular properties of body hairs, such as growth rate and follicular activity, and the impact of external factors such as cosmetic use, depend on where the hair is located. This may, in turn, significantly influence the presence of foreign chemical substances in different hair shafts.
Taking the results from both scalp and body hairs into account would ensure a more objective profile, the study authors argued, making forensic or medical evidence more robust.
Adding to an extremely limited global body of evidence on the chemical and structural differences between body hairs, the study authors said they found that eyebrow and leg hairs differed most from other body hairs.
Chemical screening of hair has proved crucial for forensic analysis globally, especially for post-mortem toxicology. Mane samples taken from the preserved remains of the famous racehorse, Phar Lap, were used to determine nearly two decades after its death in 1932, that the horse died from ingesting a massive dose of arsenic.
