Illustrated Guide to Home Forensic Science Experiments

Part VI. Impression Analysis

Impression analysis makes up a significant part of the workload of any forensic laboratory. Any time an object is pressed into contact with another object, an impression may result. For example, the tread of a shoe may be impressed into snow, mud, soft dirt, or a carpet. A hit-and-run driver’s vehicle bumper may leave characteristic impressions in an object he strikes, or even on the body of his victim. A burglar’s crowbar may leave characteristic impressions on a door frame or striker plate, and the pliers used by a terrorist bomb maker to cut wires may leave characteristic impressions on the wire.

Impressions are useful primarily to the extent that they are individualizable. Primarily, but not exclusively. Consider ...