• Firearms and tool mark evidence are important classes of physical evidence. • Important patterns for individualization include those left behind on fired evidence,
in tool marks, and in writing. • Rifling was added to the barrels of firearms to impart spin to the bullets, which
increased accuracy and range. Additionally, this process impressed into the barrels of firearms individualizing characteristics that help connect a bullet and/or car- tridge casing to a particular firearm.
• Bullets can be identified to a particular weapon using a comparison microscope to examine the individual characteristics.
• Gunshot residue can be identified on the hands of a person, but this finding does not show that the person fired a weapon.