Identification Techniques Used for Firearms, Tool Marks, and Other Impressions
“The examination process typically begins when an examiner receives a suspect firearm, along with bullets (the projectiles) and spent cartridge cases recovered from a crime scene.” …show more content…
The inner workings of a firearm which are responsible for creating impressions on a bullet are as follows: the firing chamber, breech face, firing pin, ejector, extractor and the rifling of the barrel. Characteristics transferred to the cartridge case include: firing pin impression, center of firing pin impression, and ring of firing pin impression. In a study by Md Ghani et al in 2010, 96.7% of the time these features were able to connect the cartridge case to the firearm. (http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNLAB.html).
Tool marks, which are any “impression, cut, gouge, or abrasion caused by a tool coming into contact with another object” (Saferstein, p. 232) are frequently found at crime scenes involving burglary or other forced entry into a building or safe. Typically, tool marks can be made via the use of screwdrivers, knives, or crowbars. The result is an indentation left by the prying action of such implements. Because tools are manufactured with microscopic irregularities, they leave these markings on whatever soft surface they are pushed upon. Simple use of a comparison microscope can determine what appear to be