RENO, Nev. -- The idea that a person's home is their castle and they have the right to kill trespassers has been widely accepted in the U.S. for more than a century.
But that broad legal premise has been put to the test in several states amid cases that stretched the boundaries of "stand your ground" self-defense laws.
The latest high-profile case is in Nevada, where a man is on trial on murder charges after opening fire on two trespassers - not in his home but at a vacant rental unit he owns.
In neighboring Utah, a man was hailed as a hero after he intervened in a would-be carjacking outside a grocery store, gunning down the suspect. Months earlier, a jury convicted a Montana man who shot and killed a German exchange student trespassing in his garage.
Such cases have renewed discussions about stand-your-ground laws and how they are interpreted across the U.S.
Since Florida expanded its version of the "castle doctrine" to allow deadly force outside the home in 2005, more than 30 states have adopted or strengthened such provisions, providing more leeway to claim self-defense as a reason to kill.
Twenty-two specifically say "there is no duty to retreat (from) an attacker in any place in which one is lawfully present," according to the National Conference of State Legislatures.
In Reno, Wayne Burgarello, 74, insists he was justified in fatally shooting one unarmed trespasser and seriously wounding another after confronting them in a rundown duplex in February 2014.
Washoe County prosecutor Bruce Hahn said the former schoolteacher angry about past burglaries acted out of revenge - not self-defense - when he entered the darkened duplex and unleashed a barrage of gunfire on a man and woman beneath a comforter on the floor.
Burgarello said he thought the man pointed a gun at him. No weapon was found, but his lawyer said he might have mistaken a black flashlight police found beneath the victim's body for a firearm.
"In a split-second decision ... he shot because he believes his life was threatened in a bedroom where no one should have been," attorney Theresa Ristenpart said.
The U.S. Supreme Court first ruled in 1895 that if a property owner didn't provoke the assault and had reasonable grounds to believe such force was necessary to save his own life, he "was not obliged to retreat ... but was entitled to stand his ground."
Nuances in today's stand-your-ground laws are complicated, but that basic premise has not changed, said Jules Epstein, a professor at Widener University School of Law in Delaware who teaches self-defense theory for the Reno-based National Judicial College.
"At least in your home, you can stand your ground," Epstein said. "If a burglar breaks in, even though I could run out the back door, I don't have to."
Outside the home, states without stand-your-ground laws still prohibit use of deadly force "if you could retreat with complete safety," he said. But in most states with such laws, a person who feels their life is threatened can respond lethally regardless of an ability to walk away.
Critics say such laws are about promoting gun ownership, not protecting people's rights.
"Stand-your-ground laws have contributed to an atmosphere of vigilante justice in our society," said Tanya Clay House, the director of public policy for the Lawyers Committee for Civil Rights Under the Law who says the National Rifle Association started lobbying legislatures for such laws decades ago.
Backers say opposing groups are the same ones who long have advocated stringent gun control, fighting to ban concealed weapons and prohibit carrying them on college campuses.
"Stand-your-ground laws simply place the law on the side of victims instead of criminals," NRA president Chris Cox said.
Interpretations of the laws vary.
Utah prosecutors announced May 15 that they would not charge the bystander who killed the would-be carjacker.
But a judge made it clear in February that Montana's stand-your-ground law has limits when he sentenced Markus Kaarma to 70 years for the 2014 killing of the teenager. Prosecutors argued Kaarma couldn't claim self-defense because he was intent on setting a trap for a burglar.
In Minnesota, which still has a "duty to retreat" provision in some instances, Byron Smith was convicted of premeditated murder last year for lying in wait in his basement and killing two teens who broke in.
Jeb Bush, who signed Florida's law as governor in 2005, defended the laws last month in a speech at the NRA convention in Nashville.
"You shouldn't have to choose between being attacked and going to jail," he said.