Vehicular Locard's principle and patterned tire markings.

A 32-year-old man was found dead beside a road with severe complex traumatic brain injuries due to blunt craniocerebral trauma compatible with being run over by a vehicle. A subsequent review of closed-circuit television (CCTV) footage showed him to be unaccompanied and to fall over beside the road. At autopsy, distinctive black patterned markings were present on the left side of his face and head, which were not associated with significant underlying patterned bruising or abrasions. These corresponded to the pattern of tire tread taken from a vehicle identified by police as likely to have been involved in the incident. This case demonstrates an unusual form of tire track marking on the skin due to the transfer of oil/dirt/rubber from the projecting tread, that is, a vehicular form of Locard's principle where every contact leaves a trace. Although this may be extremely useful in linking a particular vehicle to a crash, the superficial nature of the residue renders it vulnerable to being wiped off by rubbing with a body bag during transport or washing if a body is cleaned. Careful photographic documentation of such tire markings at the scene will preserve this type of evidence and avoid it being subsequently compromised by body handling.