Microscopic observation of the shell can reveal the characteristics of the firing pin, the marks left by the hook and the bolt, the rifling of the warhead and the characteristics left by the barrel. By comparison, different guns can be distinguished.
Trajectory analysis is to analyze the ballistic characteristics by observing the environment and the hit state, such as analyzing the shooting distance according to the residual and destructive power of gunpowder and the shape of warhead, inferring the incident angle and trajectory according to the environmental conditions such as the hit position, and thus inferring the shooting position and possible gun type.