Investigation into DNA transfer during physical child abuse

The overall aim of this investigation was to determine whether DNA transfer can be used to identify perpetrators of physical child abuse. To this end two separate investigations were performed: First, 12 areas of the head/neck of 32 children aged 0-5 years of age were swabbed in order to determine the ‘normal’ background levels of DNA present. The results indicated that person-to-person variation accounted for the differences in DNA profiles retrieved, while little non-subject DNA was observed. The second part of the investigation was to determine if DNA is transferred during forceful contact, such as slaps and punches. This half of the study was divided into three phases: firstly 15 volunteers were asked to punch and slap a DNA free acetate sheet attached to a focus pad, 15 minutes after washing their hands. On a separate occasion they were asked to repeat the experiment but with an hour interval between hand washing and contact as well as with three punches/slaps rather than just one. Phase II was a preliminary test of person-to-person forceful contact involving two members of the Forensic Pathology Unit. Finally sixteen volunteers applied single punches/slaps to the upper arm of another volunteer. The results from all three phases indicated that DNA transfer does occur, onto DNA-free surfaces and between individuals, although the profiles retrieved varies between individuals. Slaps resulted in more transfer than punches, while no difference was observed between single and multiple (n = 3) contacts. Many of the volunteers exhibited non-subject alleles of unknown origin on their hands and arms which complicated interpretation. Overall both studies indicated that perpetrators of physical child abuse may be determined by the DNA they deposit during forceful contact although the person-to-person variation observed means further research is necessary in this field.