Wellington OPP report that they need to know the “time” when a collision occurred on the Woolwich-Guelph Town Line and Lerch Road.This might help in identifying the deceased found the Black Pick-up truck that was reportedly found “deep” within some trees. The OPP provided the photo below showing the vehicle.

This is an example of a situation where training in the interpretation of physical evidence caused in motor vehicle collisions is needed. Aging of evidence cannot be understood without substantial contact with that evidence. For example the above photo shows several tire marks in the snow in the foreground. If these tire marks had been found by investigators upon their first arrival they would have wanted to know what type of vehicle caused them, when the marks were caused and what motions the vehicle (or vehicles) were performing when the marks were created. The mistake of blindly believing a witness who tells the investigator how the marks were caused could be fatal to an investigation. Conclusions must be drawn independent from what the investigator is told.

Unfortunately most police investigators are not trained to understand the detailed characteristics that exist in tire marks. Police study the basics of tire marks on hard surfaces and only in relation to those marks that are caused just before, or as a result of a collision. But much more can be gained, not only from looking at collision-related tire marks on hard surfaces. As can be seen in the above photo, tire marks can be created in a vast range of situations and conditions. Tire marks in snow and gravel for example are much different and their aging is vastly different than what may occur on hard surfaces. The specific quality of the surface upon which the tire mark is made with govern how the mark will age and how it will appear or when it might no longer be visible.

Even visibility is relative. We have often stated that “Visibility is in the mind of the beholder”. That is, a novice who looks at an aged tire mark may find that it is invisible yet a trained and experienced expert may have no trouble seeing it.

The environmental conditions, rain, snow or wind can be important in changing a tire mark’s appearance. Growth of vegetation or existence of animal or human activity will also be factors that can change the appearance of tire marks over time.

The professional investigator will maintain an atlas of tire marks created in all possible conditions, by all possible vehicles, in all possible actions so that this can be used as a reference when encountering a situation where information needs to be obtained that could be crucial to the progress of an investigation.