. Forensic specimens are examined microscopically using different types of microscopes, e.g. compound light microscopes, phase contrast microscopes, polarizing light microscopes and comparison microscopes.
Firearms examiners use stereomicroscopes to compare bullet casings or bullets for markings (Forensics, 2005, 229-230). Automatic and semiautomatic weapons work either by blowback, recoil or gas piston (391-392). Basically, in firing a gun, the trigger is pulled, which causes the hammer to hit the back end of the bullet, which contains a primer which ignites the powder (Class, 2005). This explodes and the expanding gas propels the bullet from the gun.
When a gun is made by hollowing out a metal rod, the process may leave marks on the inside of the chamber known as rifling which can be used to match bullets to the gun they were fired from because it leaves these patterns on the bullet casing (Forensic, 2005, 395). A firing tank filled with water is used to collect fired bullets for comparison to those found at a crime scene (229). A firing target allows the examiner to look at gunpowder or pellet patterns when a gun is fired at different distances from the target. Gunshot residue can determine the weapon used, the target distance, and link the gun to the shooter. The residue comes from the gun muzzle and barrow and is deposited on the hair, nails etc. of the person holding the gun (Class, 2005).
Toolmarks are examined in burglaries where they have been used to gain entry (Forensics, 2005, 230). Documents are examined for alterations, obliterations, erasures, ink characterizations, and for verification of authenticity of the author. In typed or computer-generated documents, defects in the printing ca
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