MISSOULA, Mont. — Markus Kaarma, a 30-year-old Montana man, was convicted of deliberate homicide for shooting Diren Dede, a 17-year-old German exchange student caught trespassing in his garage. Kaarma's attorneys unsuccessfully argued his actions were justified by a state law allowing the use of deadly force if a person reasonably fears for his or her safety or their property. Some key legal issues raised by the case:

Q: What was Kaarma's defense?

A: Markus Kaarma's defense attorney invoked Montana law allowing people to use deadly force to defend their property — a centuries-old concept known as "the Castle Doctrine." That law was expanded in 2009 to allow the use of force even in cases that don't involve violent entry.

Q: What did Kaarma do that led to his trial?

A: Kaarma killed Dede after the youth entered his garage unannounced in the early morning of April 27. Kaarma had told witnesses he was frustrated with burglars and was laying a trap for one. That night, he left the garage door ajar, a purse visible and waited inside with a shotgun.

Q: Is that sort of behavior allowed under the Castle Doctrine?

A: Not necessarily, which is why Kaarma was convicted. He had to demonstrate he was reasonably fearful for his safety. A jury concluded he was not. In a similar case, a Minnesota man was convicted in May of lying in wait in his basement for two teenagers and killing them during a break-in.

Q: Do other states have these laws?

A: At least 30 states have strengthened their self-defense laws since 2005. Florida kicked it off with its "Stand Your Ground" law that allowed the use of deadly force in more circumstances outside the home. Montana expanded its own self-defense law in 2009. The principle came under national scrutiny in the 2012 shooting of an unarmed Florida teenager, Trayvon Martin, by a neighborhood watch volunteer who was following the 17-year-old. George Zimmerman was acquitted last year after arguing self-defense.

Q: Does Germany have a similar law?

A: No, which is part of the reason Kaarma's case attracted so much attention in Germany.

Q: What happens to Kaarma?

A: He faces a minimum of 10 years in prison and is scheduled to be sentenced in February. His lawyer says he's planning an appeal.