| Hair is a common form of evidence found at crime scenes, and may be the sole trace evidence to tie a suspect or victim to a location or crime. Isolating DNA from head or pubic hairs is an attractive means of placing a suspect and/or victim at a crime scene. Nuclear DNA is thought to be degraded or not present in shed (telogen) hairs, making STR analysis using commercially available kits difficult or impossible. MtDNA analysis of hair shafts is often successful, but many labs have not validated the method, and in the end, it is not an absolute identifier. Likewise, DNA isolation from hair shafts involves laborious extraction techniques, which can increase the likelihood of contamination. An alternative to standard DNA isolation from hair shafts is alkaline extraction, in which keratin from hair is hydrolyzed but DNA is kept intact. This method was used to extract DNA from head and pubic hair shafts. Hairs were washed in an enzymatic detergent, and then rinsed with ethanol and water. The hairs were then incubated in concentrated sodium hydroxide until completely dissolved, neutralized, and DNA eluted in TE on a spin column. A 220bp product of mtDNA was obtainable from 68% of alkaline digested head hairs and from 98% of alkaline digested pubic hairs. Hair DNA that successfully generated mtDNA product was tested on single and multi-copy nuclear markers. Multi-copy markers show promise as possible sex determinates, while small single copy loci have real-time PCR applications. |
