The markings produced when one object comes into contact with another, leaving behind some kind of indentation or print, are known as impression or tool marks. These marks occur when enough force is applied to leave a three- dimensional indentation on the softer surface by a harder tool or object. There are two main types of tool marks:
- Impression marks: Created when a tool is pressed against another object with sufficient force, leaving an indentation, like a crowbar used to pry open a door leaving an impression.
- Striation marks: Created when a tool moves across another surface with pressure, creating scratches or slicing marks.
These markings carry characteristics from the tool, including:
- Class characteristics: General features designed by the manufacturer, like size and shape.
- Individual characteristics: Unique incidental marks from the tool’s usage or manufacturing defects, acting like a fingerprint of the tool.
Impression evidence broadly includes any such markings from one object contacting another, such as fingerprints, shoeprints, toolmarks, and tire treads. These markings help in forensic analysis to link tools, weapons, or individuals to a crime scene by examining these indentations or prints left behind through contact.
