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A tool mark is considered to be any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object. Most often, tool marks are encountered at burglary scenes that involve forcible entry into a building, but also are encountered in homicide cases where an axe or knife strikes bone. Generally, these marks occur in the form of indented impressions into a softer surface or as abrasion marks caused by the tool cutting or sliding against another object.

Just as firearms possess and leave individual characteristics from their manufacture and use, so do tools such as pry bars, chisels, axes, knives, etc. leave marks that can be used to positively identify the use of a particular tool. Tool marks examinations are a comparative examination, where a tool mark or cast of a tool mark are compared with known tool marks produced in the laboratory by the suspect tools. The known and unknown marks are compared microscopically using a comparison microscope.

Tool mark on metal wire

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