We’ve known for years that DNA can be obtained from hair and this can be used for identification. If part of the follicle, or bulb, is present, then nuclear DNA can be retrieved and a complete DNA profile can be created. If only the hair shaft is available, then mitochondrial DNA is available and this can help narrow the identity of an individual by showing that the person belongs to a specific maternal line. Not nearly as good as nuclear DNA but this does focus the suspect field to a single maternal line.
But what if the hair shaft could be even more discriminatory? What if it could ID a specific individual and not just someone in the maternal line? Most hair found at crime scenes has been shed naturally and therefore has no follicular material, which might be present if the hair had been yanked free. This means that typically only mitochondrial DNA is available to the crime lab.
But new studies have found an ultra-sensitive method for determining proteins within the hair shaft itself and it turns out that the types and amounts of the proteins present might be highly specific from individual to individual. This technique obviously is not ready for prime time yet, but it’s something to keep an eye on.
Science Article: https://www.sciencemag.org/news/2019/11/scientists-can-now-identify-someone-single-strand-hair