How can two shotgun shells be compared in CSI?

How can two shotgun shells be compared in CSI?

Richard Saferstein (Former Chief Forensic Scientist) gives expert video advice on: How does the study of firearms help in CSI?; How does a gun work?; How are firearms and ammunition collected in CSI? and more...

Unlike a rifled weapon, the inner walls of a shotgun are smooth and therefore do not contribute markings to the pellets that travel through the barrel. It is the cartridge casing that may be deposited at the crime scene that is left with unique markings, whether it be breach-block markings or firing pin markings, and these types of markings are what the firearm examiner will study and compare when it comes to the identification and individualization of a shotgun.