Evaluation of a decontamination protocol for hair shafts before mtDNA sequencing

Mitochondrial DNA (mtDNA) sequencing is a powerful and sensitive method to identify the donor of shed hairs found at a crime scene. Because of the low amounts of DNA in shed hair and the sensitivity of PCR, contaminating cells (e.g. saliva, blood), sometimes present on these hairs, will be co-amplified. This will result in ambiguous sequencing results and might even lead to erroneous exclusions of suspects. We have evaluated a strategy for effectively removing saliva and blood contamination from hair samples. Unambiguous mtDNA results were obtained by incubating the hair samples in a differential lysis buffer (which contains no DTT) prior to DNA extraction. Since the nuclear DNA of the hair root is affected, this procedure should be restricted to hair shaft proportions.