Tool Mark Examinations and Comparisons
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          Tool marks are those marks produced by an object when it come into contact with a softer substance and either scrapes or cuts across it or is impressed into it. There are many examples of tool marks in our environment. A common one is shown in the photograph on the left where a pair of bolt cutters was used to cut a lock shackle. The comparison micro-photograph shows the evidence lock shackle on the left side and the test cut produced by the bolt cutters in a piece of lead on the right.

          An unusual example of a tool mark comparison is shown on the left where a knife edge from a suspect's knife was compared and matched to a piece of rib cartilage from a victim. On the left is a silicone rubber cast of the cut in the victim's rib cartilage compared with a cast of a test cut produced with the suspect's knife using a plastic material (Dip-Pak). A close-up of the defects in the suspect's knife edge which produced the toolmarks seen in the cut is shown in the following photograph.
The photographs below show some other unusual types of toolmark comparisons.







A button comparison showing a button found at the scene of a crime
versus a button from a suspects' shirt










A "pop-top" pull tab comparison










A pop-rivet comparison










An air-gun pellet comparison