Advances in the DNA analysis of canine trace evidence for serious crime investigation in the UK

Non-human evidence is becoming widespread in serious crime investigations. Canine hair samples have proved especially useful due to the high rate of transfer that naturally occurs between dogs, people and property. A murder investigation in the UK during 2008 provided the opportunity to undertake further research into the application and limitations of non-human hairs for linking victim to suspect. The overall aim of the work was to maximize the genetic data that could be obtained from shed hairs. This was attempted by conducting four short experiments to examine: (i) the recovery of exogenous human DNA from the surface of hairs, (ii) the potential for canine DNA originating from saliva to be obtained from hair shafts, (iii) the presence of residual DNA on tape lifts following hair removal and (iv) the potential for enhanced profile recovery following whole genome amplification of canine DNA. Results showed that DNA could be recovered from the surface of hairs following simulated licking and skin contact. When applied to casework samples, additional human DNA evidence was recovered from dog hairs in this manner. Attempted DNA recovery from tape lifts was unsuccessful. Whole genome amplification improved the recovery of full and partial profiles under reducing DNA concentration. The work demonstrates several novel approaches for recovering trace genetic evidence from animal hairs. Although such detailed analysis is unlikely to be applied to routine casework investigations, it increases the range of forensic tools available to investigate serious crimes.