By its means it can generally be demonstrated whether the shooting was accidental or intentional--and whether or not the killing was in self-defence.
Where this last plea is interposed it is usually made at once upon the arrest, the accused explaining to the police that he fired only to save his own life.

In such a situation, where the killing is admitted, practically the entire preparation will centre upon the most minute tests to determine whether or not the shot was fired as the accused claims that it was.

The writer can recall at least a dozen cases in his own experience where the story of the defendant, that the revolver was discharged in a hand-to-hand struggle, was conclusively disproved by experimenting with the weapon before the trial.

There was one homicide in which a bullet perforated a felt cap and penetrated the forehead of the deceased.

The defendant asserted that he was within three feet of his victim when he fired, and that the other was about to strike him with a bludgeon.