To prove that a particular gun was used as a murder weapon, forensic
scientists have to go through the laborious process of comparing the suspect
bullet under a microscope with a fresh bullet fired from the gun. Now the
Canadian company Walsh Automation of Montreal is filing patent applications
on a computer system which does the work automatically (WO 92/20988).
All bullets carry striations on their surface, caused by irregularities
in the barrel. Walsh’s system clips each bullet in turn to a rod which rotates
slowly under the lens of a microscope mounted on a video camera. As the
bullet turns, the camera builds up full TV image of the surface area of
the bullet.
The TV image is then converted by a computer into digital code, so the
striations are represented by a sequence of numbers. The number pattern
for any two bullets can then be compared easily by a computer operator.
If the numbers match, an expert can examine the bullets by eye to make a
final decision and, if necessary, testify in court. This system saves time
by automatically checking and dismissing bullets which do not match.
