Chapter 9
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What is the function of grooves rifled into the bore of a gun?
To spin the bullet, stabilizing it for improved accuracy and trajectory.
What are the three most common types of handguns?
Revolver: Rotating cylinder, multiple cartridges. Semi-Automatic Pistol: Uses a magazine, reloads automatically. Single-Shot Pistol: Fires one round before reloading.
How do gunpowder residue patterns vary with distance?
Close Range: Dense soot and residue. Intermediate Range: Stippling (powder burns). Distant Range: No visible residue or stippling.
How does a shotgun barrel differ from a rifle barrel?
Shotgun: Smooth barrel, no rifling. Rifle: Rifled barrel, grooves and lands for bullet spin.
What tool is used to compare bullets?
A comparison microscope.
What does a shotgun’s gauge reflect?
The diameter of the barrel, defined by the number of lead balls of that diameter needed to weigh one pound.
What can make distinctive markings on shells and cartridges?
Firing pin. Breech face. Extractor and ejector mechanisms.
What are two tests to detect gunpowder residue?
Greiss Test: Detects nitrites. Sodium Rhodizonate Test: Detects lead residues.
How should a firearm be handled to preserve latent fingerprints?
By the trigger guard or non-grip surfaces.
How should a firearm recovered from underwater be packaged?
Submerge it in the same water it was found in to prevent rust or corrosion.
What should be done with tool marks if the object cannot be submitted?
Create a cast using silicone or other suitable materials.
How should firearms evidence be collected and packaged?
Ensure the firearm is unloaded. Document its condition. Package in a rigid container. Package bullets, casings, and cartridges separately in labeled containers.
What two elements are detected on hands after firing a weapon?
Barium and antimony.
What does the distribution of gunpowder particles and residues indicate?
The distance from which the weapon was fired.
What is NIBIN?
The National Integrated Ballistics Information Network, used to compare ballistic evidence like bullets and cartridges to link crimes.
What are the possible results of laboratory firearm evidence examination?
Match bullets or casings to a firearm. Determine firearm type. Analyze gunpowder residue patterns. Estimate the range of fire.