This discipline of the area of firearms expertise concerns that which occurs from the instant the firing pin touches the primer until the projectile exits the muzzle and the pressure in the barrel drops to one atmosphere. This includes such issues as firing pin embedment into the primer, the transfer of machining marks onto the surface of the primer, the generation of the propellant gases within the firearm, engravement of the rifling, and all else contained within the definition of interior ballistics.
In particular, LTC Alphin’s skills as an Interior Ballistics Expert enabled him to correctly evaluate the dynamics of firing pin embedment. This, in turn, has led to debunking attempts by prosecution “experts” to link certain expended cartridge cases to a certain firearm. This was a factor in both the Jenkins and Holmes cases. In initial consultation on other cases, just this knowledge alone has helped defending attorneys shape their theory of the case.