ST. LOUIS • William J. Whitfield came home early one January morning in 2010 to find his tiny brick bungalow just about emptied out by burglars.

They took his tools, his computer, his flat-screen televisions.

"They tried to get my washer and dryer too, but that was bolted to the floor," said Whitfield, 66, a retired Navy petty officer who lives in the city's College Hill neighborhood.

But the burglars left something else behind: bags stuffed with more of Whitfield's belongings, stacked near his basement stairwell.

He knew they would be back. So, he called police to report the burglary, but he also armed himself with his 9 mm pistol and slept in a chair in the front room that night. And when three people broke in about 3 a.m., Whitfield shot one of them, leaving the man dead on the kitchen floor.

Police investigated the shooting, but Whitfield never really faced the prospect of prosecution. Missouri's expanded self-defense law, passed in 2007 and known as the castle doctrine, not only protected him from being charged but meant he couldn't be sued over his actions that night.

Whitfield's case is just one example of homeowners taking action against intruders — and burglars dying at the hands of those homeowners. Supporters say the law is working, but not all cases are clear-cut, and authorities have struggled with the evolving law and increasing numbers of shootings that seem to fall under it.

Within 72 hours in September, two burglars were fatally shot in homes on opposite ends of St. Louis. Police said both homeowners were justified. And in early December, an off-duty Beverly Hills detective who lives in St. Louis shot a burglar to death under nearly identical circumstances.

In total, there were seven fatal shootings that involved the castle doctrine or other self-defense laws in St. Louis last year, compared with two in 2010.

St. Louis police are changing how they handle apparent justifiable homicide cases in response to the spate of such shootings.

In the past, detectives and supervisors in the St. Louis Police Department's homicide unit who thought a homicide was justified would call prosecutors to run it by them, to make sure they agreed.

"If the victim was able to articulate that they thought their lives were in jeopardy, along with being supported by physical evidence and/or witness statements, it was deemed justifiable," said Capt. Michael Sack, head of the department's homicide unit.

Now, Sack said, every case will undergo a more formal review by the St. Louis circuit attorney's office.

"It seems to make sense to ask someone else to review our investigation and our work and see if they come to the same conclusions as we do, especially when you're talking about something as serious as taking someone's life," Sack said.

EXPANDED LAW

Whitfield's shooting of an ex-con who had served time for burglary and weapons charges might be a classic castle doctrine case, but in a recent interview, Whitfield wasn't boastful.

"You don't kill somebody and feel good about it," he said quietly.

He had never even heard of the castle doctrine when he fatally shot the intruder.

"I was worried for my safety," Whitfield said. "I just figured if somebody breaks in, you have a right to defend yourself."

Before the castle doctrine, that wasn't strictly true.

Under the state's old law, homeowners confronted by intruders had a duty to escape their homes if they could do so safely. If they couldn't get out, the homeowner could only use deadly force to protect from serious injury or death.

Under the castle doctrine, people who encounter an intruder in their homes or vehicles — or on their property, under a more recent expansion of the law — are given more leeway in using deadly force.

The law allows you to use that force without fear of being charged or sued.

People in Missouri can repel intruders on the theory that anyone breaking into an occupied home has evil intentions toward the residents, said Kevin Jamison, a lawyer from Gladstone, Mo., who lobbied for Missouri's castle doctrine bill as a member of the Western Missouri Shooters Alliance. The law now covers you even if you fend off a carjacker or confront an intruder in your tent in the woods.

The law can be complicated, and interpretations can differ, but the crux is whether the homeowner is put in fear of "unlawful force." If so, he or she can use lethal force.

The Legislature didn't define "unlawful force," leaving it for others to interpret.

"If the burglar just has a mean look on his face and he's advancing toward you, for most people, that's enough to put you in reasonable fear of unlawful force," Jamison said.

Even if you only feared a slap, that would be a fear of unlawful force and would allow you to shoot an intruder, according to Cape Girardeau County Prosecutor Morley Swingle, who served on the Missouri Supreme Court committee that wrote jury instructions for the new self-defense law.

'SHOOT-FIRST LAWS'

About 30 states have some form of a castle doctrine, according to the National Rifle Association. Illinois has a general self-defense law, but the NRA doesn't consider it a castle doctrine law because it puts too much burden on the homeowner, a spokeswoman said. State law there allows deadly force only if the intruder enters in "a violent, riotous, or tumultuous manner," or if the homeowner believes deadly force is the only way to prevent the intruder from committing a felony.

When the Missouri law was debated, proponents said it would help deter crime and empower homeowners.

"Let's let the criminals wonder whether this will be their last crime," then-Rep. Curt Dougherty, D-Independence, said in one House debate on the castle doctrine.

Critics worried it would encourage vigilantism or be used as cover for someone who wanted to commit premeditated murder. Another scenario still feared by critics: What if the "intruder" is actually an innocent person who bursts into your home seeking medical aid?

"We call them 'shoot-first laws,'" said Brian Malte, director of state legislation for the Brady Campaign to Prevent Gun Violence. "Shoot first, ask questions later."

Swingle, the prosecutor who helped write jury instructions on the castle doctrine, said the committee of lawyers and judges discussed hypothetical situations that could arise. For example, what if a burglar passed out drunk in your house? Can you execute him?

"We decided that reasonableness should still apply," Swingle said. "You have to have a reasonable belief that it is necessary to defend yourself from the imminent use of unlawful force."

JUSTIFIED HOMICIDES

It's not clear how many times the castle doctrine has been used as a defense in Missouri. The real effect, Swingle said, is likely in cases never filed by prosecutors.

In 2008, Missouri's castle doctrine faced its first test when a Kirksville woman fatally shot a man who crawled through her window in violation of a restraining order. After some local discussion about whether charges were warranted, it was Missouri Attorney General Chris Koster who made the call: No crime was committed. The woman was justified to shoot under the castle doctrine.

Prosecutors did file charges after a 2008 shooting in a St. Louis home but couldn't get a conviction.

They pressed a case against a woman who, during a fight over a bag of fast food, fired a shot at a man who was dating her niece. The woman missed, and instead hit the niece, who died.

Prosecutors said the woman was angry. The judge was convinced she was afraid of the man and found her warranted in using deadly force under the castle doctrine, and not guilty even though she had killed the wrong person with that force.

In a case earlier in 2011, a man broke into his ex-girlfriend's St. Louis home and tried to attack her, according to police. Another man who was also in the home came to the woman's aid and pointed a gun at the intruder, Emmett Terry, but didn't shoot.

Instead, he handed the gun over to the woman, who pointed it at Terry as he stood with his back to a wall, according to police. The woman's friend helped her steady the gun and point it at Terry.

"I told you if you came back, I was gonna kill you," she said before fatally shooting him, according to police reports.

St. Louis police thought the killing of Terry in April was a crime and sought second-degree murder charges against the woman and the man. But prosecutors declined to file them because the shooting could be justified under the castle doctrine.

The Associated Press and Christine Byers of the Post-Dispatch contributed to this report.