Most people who buy a firearm for self-defense are never confronted by a likely attacker. A few are, though, and they have to make split-second decisions that can change their lives and many others forever.

"The world is a dangerous place," said Dr. Phillip Broadhead, clinical professor of law at the University of Mississippi. "Sometimes you're forced to protect yourself, but sometimes you may perceive a situation as more dangerous than it really is, and the wrong response could cost you everything. On the other hand, if you perceive it as less dangerous than it is, you could lose your life."

Broadhead said three elements are required for the use of deadly force to be lawful - aggression, immediate means to do serious harm, and a reasonable response on the part of the potential victim.

"Another person has to be the first aggressor," he said. "You can't start problems with someone, have them escalate and then respond with deadly force."

The aggressor also would have to have the immediate means to carry out the perceived threat - "being armed with a gun, a knife, a baseball bat, for example," Broadhead said. Shooting an aggressor inside a house because he has a gun in his car, as another example, would fail the immediate-means test.

The potential victim can meet force with force, but it must be in proportion.

Oxford attorney Reed Martz said citizens are "entitled to use whatever reasonable force is necessary to protect (themselves or other innocent parties) from imminent great personal injury."

He noted, however, that "a person will rarely be justified in shooting an unarmed aggressor unless the aggressor's size, training or method of attack is such that a reasonable person would fear great personal injury was about to result."

Mississippi law includes the so-called "Castle Doctrine." It allows occupants of a home, a vehicle or a business during non-business hours to presume anyone forcibly entering presents a threat of death or serious bodily harm. It also holds the occupants immune from civil or criminal prosecution for using deadly force in such a situation.

The Castle Doctrine is not without limits, however.

"The law does not look with favor on the use of deadly force merely to protect property," Martz said. "It is not justified to shoot someone for stealing a lawnmower out of your front yard. But if a criminal breaking into your garage in the middle of the night to steal that same lawnmower causes you to fear for your safety, at that point you would be justified in using defensive force."

Ben Creekmore, district attorney for Mississippi's Third Judicial District, said, "If somebody you don't know pulls into your driveway and you feel threatened ... and start shooting at the car, that's the Castle Doctrine gone wrong - and that has happened. The people who pulled into the driveway were simply trying to turn around and go the other way.

"If people don't use good judgment, it can get them in a lot of trouble," Creekmore said.

Contact Errol Castens at (662) 281-1069 or errol.castens@djournal.com.