How to Compare Shotgun Pellets at the Crime Lab

Crime labs compare shotgun pellets to determine different factors about gunshots.

Shotguns fire cartridges loaded with small metal pellets through a barrel with a smooth lining or bore. Bullets from other guns have marks from the inside rings of a barrel, but pellets have no telltale signs that lead to the weapon. However, a crime lab comparison of shotgun pellets offers analysts other types of information.

Physical Characteristics

Forensic scientists compare the size and shape of shotgun pellets. Size can determine the gauge, or the diameter of the shotgun barrel, which can help identify a weapon. Pellets made of lead, steel and tungsten travel at different speeds and react differently on impact. Comparing spent pellets to test shots can determine the distance and angle of a gunshot.

Wadding

Shotgun shells are packed with wadding, usually a plastic or paper buffer, that protects the pellets from the heat and force of gun power. Some pellets may have traces of wadding that may identify the manufacturer and retailer of the ammunition.

Pellet Spray

Analysts examine the spray pattern of shotgun pellets and compare it to patterns from test shots to determine the location and distance between the shooter and the target. Spray patterns may also reveal whether or not the shotgun barrel has a choke, a slight narrowing, that affects how pellets are dispersed.

References

• Forensic Science Encyclopedia: Shotgun Cartriges
• Firearms I.D.: Shotgun Pattern Testing
• Elizabeth Marshall: Forensic Lectures: Ballistics Slides
• Mossberg: Barrels and Sites
• Briley: Understanding Shotgun Chokes