ST. LOUIS - A homeowner who shot and killed a burglar early Monday morning most likely will not be charged with a crime, police said, because his actions are protected under Missouri's "castle doctrine" law.

Missouri's "castle doctrine" allows people who encounter an intruder in their home to use deadly force to protect themselves.

Monday's shooting is the second in less than a month in St. Louis where the "castle doctrine" comes into play.

In the case on Monday, a 64-year-old man killed the burglary suspect, 45, after he broke into a house in the 1900 block of College Avenue about 3:45 a.m. Monday. The homeowner shot him in the chest. Two women who also broke into the home then ran from the scene.

The man's home also had been burglarized over the weekend, sometime between early Saturday and early Sunday morning, police said. Police continue to search for the two female burglary suspects.

The name of the burglary suspect who was killed has not been released pending the notification of family members. The homeowner's name also was not released. Attempts to contact him were unsuccessful.

In late December, a man shot and killed an apparent thief taking his pickup. St. Louis prosecutors have not yet decided whether to file charges in connection with the Dec. 27 incident, which raises questions about where to draw the line on use of deadly force.

Police said a man, 31, whose name has not been released, started his truck about 10 a.m. outside his home in the 8400 block of Church Road and left it running when he went back inside.

After someone jumped in and tried to drive it away, officials said, the owner bolted from the house and fired several shots. The truck coasted to a stop with Charles W. Kemp, 18, of St. Louis, fatally wounded behind the wheel.

Police arrested the owner on a warrant from another jurisdiction. Prosecutors are considering whether the shooting was justifiable homicide, murder or something between.

St. Louis police said the investigation results were turned over to the circuit attorney's office on Dec. 30. No decision has been made.

The "castle doctrine" also applies to an occupied car and allows a person to use deadly force against someone unlawfully committing a forcible felony such as kidnapping or rape. But there are restrictions.

Regarding a vehicle theft, Missouri law appears to allow deadly force only if the victim was inside it, or otherwise in physical danger.

Steven Beckett, a law professor at the University of Illinois, said in a recent interview that prosecutors may be inclined to charge a crime if the danger was avoidable or there was no risk of bodily harm.

He said prosecutors have wide discretion in cases like this, including the prerogative to file a lesser charge, such as involuntary manslaughter.

Illinois laws on deadly force are similar to Missouri's.

"In cases like this, you have to ask the question: 'What would a reasonable man do?'" Beckett asked. "Would a reasonable man shoot someone stealing his pickup truck? I don't think prosecutors would be wrong to charge him if there wasn't a threat of bodily harm."

Ed Postawko, a top aide to St. Louis Circuit Attorney Jennifer Joyce, said Missouri law generally permits use of lethal force if someone invades a home or occupied vehicle. He spoke with the understanding that he was commenting generally and not about Kemp's death.

"Basically if someone is trying to get into your car, you don't have to wait for someone to flash a gun in your face," Postawko said.

He said the law is fashioned to permit people to kill to protect themselves or others against a significant threat.

"You cannot use deadly force to protect your property," Postawko said. "Property can be replaced. Lives cannot."