The manufacturing process imparts what is accepted to be unique microscopic characteristics to each tool
Many different tools are produced for the purpose of carrying out a range of specific functions. The manufacturing process imparts what is accepted to be unique microscopic characteristics to each tool. Subsequent use of the tool will result in wear and tear, which can alter this microscopic detail and add further detail in respect of wear and damage features.
Forceful contact between the tool and the item it is being used on can result in an impression or mark being left by the tool. The type of tool being used and the way that it is used will influence the type of mark left. Marks can be recovered and examined microscopically or casts can be made. A comparison between the mark in question and control marks produced with the suspect tool can produce valuable evidence.
The use of tools is most often associated with burglaries or theft when an offender has forced entry to premises by levering open a door/window or cut off a padlock. Comparisons between the levering marks and screwdrivers or levers are therefore often made as are comparisons between bolt cutters and broken padlocks.
When a tool is used in a serious crime, involving injury to a person, analysis of the marks left on the victim can be matched back to a suspect implement.