Some of these indicators are obvious at the scene. Only about a quarter of suicides leave notes. Most of the rest go for the chest, and a tiny minority go for the abdomen. Only 50 percent of shotgun suicides are in the head. 36 percent are in the chest.
Gunshots wounds are the most common method of murder in America.
Usually it is fairly obvious, by the trajectory, position of gun and other circumstances - eg armed robbery. All materials recovered at the scene or at the autopsy will be sent to the ballistics section.