Store owners routinely brandish guns for protection, often in full accordance with state law. It's easy, however, for prevention and self-defense to turn into an unjustifiable killing. Cases in Chatham County are infrequent. In January 2001, a man shot and killed a robber after watching him attack his father with a brick at their Montgomery Street supermarket. That case was ruled a justifiable homicide. But in September 1999, George L. Johnston shot and killed an intruder breaking into a truck outside Beasley Kawasaki on Ogeechee Road. Johnston was indicted by a grand jury for voluntary manslaughter. The rules are strict...