Tool-mark analysis is sometimes viewed more as an art and a skill, then a science. It requires experience, time and patience.

Tool marks are the "scratches", the striations and the permanent marks left by the use of a tool against another surface. Tool marks can be the scratches on a violated door or window, a scratch on a car, or any solid surface.

In order to compare tool marks, we have to compare the suspect mark against some samples, created by known tools. Once a "control" tool mark matches the suspect, then we know it was that tool that created the suspect mark. Every tool leaves an individual mark, and is subject to its usage, tear and wear and even manufacturing imperfections, previous impacts, etc. The tool mark comparison on the right is from a comparison test at the University of Strathclyde forensic laboratories.

Some striations are more "fancy" and exciting than others. The photo on the right is from a 9mm Luger case, manufactured by the IMI (Israeli Military Industries) and it is the same kind of ammo used in the iconic Uzi automatic machine pistol. Notice the mark at the centre of the image, created upon the firing of the bullet. Matching bullets seems more exciting in TV shows like CSI, but it is the exact process used to match a crow bar or a screwdriver that left a mark on a door.

Strathclyde Forensic makes use of specialty equipment like a comparison macroscopes to identify and match striations.