Tyre Impression Marking on the Interior Surface of Clothing in a Fatal Road Traffic Incident

Introduction

The photographic image shows the internal surface of a deceased individual's jeans, captured at autopsy, after a run-over incident involving a large agricultural vehicle which stopped at the scene. Initial inspection of the external surface of the trousers identified some mud staining but no specific findings or marks. After cutting open the garment, in order to facilitate removal of the trousers from the body, a very well-defined large vehicle tyre mark was visible, consisting of linear edged ‘zig-zagged’ components (Figure 1). This was deemed suitable for scale photography to facilitate potential mark comparison work, although this was not performed given the vehicle had already been identified. Images were taken of the vehicle including its tyres but unfortunately without scale, however the mark correlated well on visual comparison. The tyre image in Figure 1 was taken after the vehicle had been transported off scene to a storage facility, accounting for the prominent dust staining highlighting the tyre tread which was not present on the tyre at the time of the incident. The pale material forming the mark on the clothing was considered to be the superficial surface skin components that had become crushed into the trouser material, when the body was run over. This view was supported by the presence of some typical post mortem yellow-brown areas of parchmented skin damage/abrasion to the leg areas that became more prominent and defined several days after the autopsy. Only focal indistinct patterning was evident on the body. Internal examination showed the presence of multiple injuries, including crush damage to the chest and pelvis along with sheared ‘pocketing’ of the subcutaneous tissues of the thigh and buttocks, with liquified fat and blood present, related to the position of the patterned marking on the clothing.

OPEN IN VIEWER

Figure 1.

Well defined linear and ‘zig-zagged’ patterned tyre mark, formed by superficial skin components on the internal surface of trouser material. Inset image shows the tyre of the vehicle involved.

Discussion

The pathological investigation of an individual fatally struck by a vehicle should include a search for findings that can help reconstruct the dynamics of the road traffic incident, particularly to confirm whether, or not, the victim was upright or potentially already lying on the road, when vehicular contact occurred. The identification of bumper-type lower limb fractures and crush ‘roll over’ trauma forms part of this process (1,2). Also important is the documentation (and collection) of any evidence that can be used to help identify the vehicle involved. Locard's exchange principle contends that every contact, no matter how slight, will leave a trace (3). This clearly includes any relevant pathological findings on the deceased such as the rare finding of a well-defined tyre tread or bumper / bonnet component mark (4–7), usually formed by a combination of abrasion and or intradermal bruising (8). Measuring the distance of such marks along with any typical leg fractures from the heel can help to identify a particular vehicle or determine if the victim was standing at the time of impact (9). It must be noted that if there is a survival period, continuing soft tissue bleeding and healing changes can obscure or alter the appearance of any marks present on the skin surface diminishing their forensic significance.

The value of examination of the clothing in road traffic fatalities as part of the post mortem examination has been described previously. This includes the documentation or collection of glass, paint and other car component fragments (8) along with the pattern and extent of any blood distribution (5). Tyre tread marks on the external surface of clothing material for example left by oil/mud staining have also been occasionally reported (4–6). The identification of a defined tyre impression mark (that should be stable in nature) on the internal surface of clothing in such circumstances does not appear to have been previously described in the English scientific literature.

Patterned marks can be either largely positive in nature (from crushing of the skin by an impacting surface) or negative, when tissues (or material) become squeezed in between protruding components (such as the grooves in the tread of a car tyre). The mark in this case, represents a positive impression on the clothing left by skin components. Given its nature, the mark should be both suitable for potential comparison work and relatively stable over time. Analysis of tyre impression marks both at scenes of an incident and on the body surface, is well established (3,10) and can lead to the identification of a brand name and possibly the model of a tyre (3,11–13). Methods of comparing defined impression marks on the body with suspected vehicular tyre treads include classic 2-D overlay methods and 3-D matching using forensic photogrammetry as described by Thali (10).

Conclusion

This case re-iterates the need for the pathologist to examine the clothing internally as well as externally, wherever possible as part of the post-mortem investigation of a road traffic incident. This will be more difficult if the clothing has been removed prior to receipt of the body to the mortuary and if heavily bloodstained. We would advise that the police investigators pro-actively retrieve (and if necessary, carefully dry and handle) such clothing, to facilitate a later pathological review and potential forensic mark comparison process, particularly when there is medico-legal uncertainties or challenges, around the dynamics of the fatal incident.