Hearing of retired cop who shot moviegoer puts Florida's controversial 'stand your ground' law back in the spotlight At least 22 states have similar legislation.

 -- Vivian Reeves was emotional as she testified Wednesday before a judge at her husband's hearing in Florida, attesting that her husband, Curtis Reeves, a retired Tampa police captain, had his head in his hands after he shot a fellow moviegoer over a disagreement about a cellphone in January 2014.

Curtis Reeves is accused of fatally shooting Chad Oulson. The shooting allegedly happened after Oulson threw popcorn at the Reeves for being told to put away his cellphone during the movie's previews.

"It happened very quickly, and [Oulson's] whole upper body just came forward, and I thought that he was coming over,” Vivian Reeves testified.

If a Pasco County, Florida, judge determines that Reeves was acting in self-defense and his case meets Florida's "stand your ground" law criteria, he will be immune from criminal prosecution and civil action in connection with the deadly shooting, according to The Associated Press. If not, he will be tried on a second-degree murder charge for the death of Oulson.

Florida's "stand your ground" law allows residents to use force, including deadly force, if they "reasonably believe" they are at risk of death or great bodily harm. The law specifies that people have "no duty to retreat" if they feel threatened.

Reeves' lawyer has invoked the "stand your ground" law. He argues video from the movie theater shows that Oulson attacked Reeves first and that Reeves acted in self-defense, the AP said.

Oulson's widow, Nicole, told ABC News in 2014 that her husband was texting the babysitter, who was watching their young daughter.

"It was a couple of words. No threats. No harm. No nothing," she said.

Why Florida's 'stand your ground' law was enacted

On April 26, 2005, Florida Gov. Jeb Bush signed the first "stand your ground" bill into law.

Republican Florida lawmaker Dennis Baxley, who co-authored the bill, which was supported by the NRA, told ABC News this week that the law was inspired in part by an uptick in crime after many hurricanes in the state.

"We had a lot of properties that were open and people living in FEMA trailers," he said.

He remembered one situation in which a man "was in his FEMA trailer with his wife in front of their property, and they had an intruder in the night which he shot and killed."

When "stand your ground" was signed into law, it wasn't controversial, Baxley claimed.

"We had bipartisan support. [It was] unanimous in the Florida senate. Only 20 people in the Florida house opposed [it]," he said.

The measure passed the Florida Senate 39-0 and the House 94-20. Arthenia Joyner was one of the Democratic lawmakers who opposed "stand your ground." She told ABC News today it was "a big debate back in 2005" and the law still leaves her with the same "fears that I had back in 2005."

"It hurts the chances for minorities to receive justice," she said.

Breaking the law down

Traditionally, a defendant who invokes self-defense is required to first retreat and avoid the deadly encounter if possible, Kenneth Nunn, a professor at University of Florida's Levin College of Law, told ABC News. But "stand your ground" modifies that, he said, by telling Floridians they do not have to retreat first and "can use deadly force if it is reasonable."

"What could've happened in [Reeves'] case is Reeves could have turned around and walked away. Without 'stand your ground,' we would say the person has to retreat ... but the law says he doesn't have to do that," Nunn explained.

Additionally, "stand your ground" gives the defendant a chance to claim immunity from prosecution.

"If you can claim 'stand your ground,' you can't be prosecuted at all," Nunn said. "The way we determine whether you can claim 'stand your ground' is through a pretrial hearing. At the pretrial hearing the defendant has to show ... they're entitled to the 'stand your ground' rule. [Defendants must show] they believe that they were under a threat of deadly force ... and it was reasonable [for them to use deadly force]."

If they can prove they acted in self-defense, then no charges can be brought, Nunn said.

Former National Rifle Association President Marion Hammer, who said she worked with sponsors to "perfect the law," told ABC News that "the very idea that when you're under attack that you should have to turn your back on an attacker and run away before defending yourself flies in the face of justice and the Constitution."

She continued, "'Stand your ground' law is about protecting innocent people from overzealous prosecutors and courts that have become more interested in convictions than justice."

Nunn pointed out that state lawmakers are trying to amend the controversial law.

"There's a statute that has been introduced into the state legislature shifting the burden of proof to the prosecution ... If this law passes, the burden will shift to the prosecution" to prove that the defendant cannot claim "stand your ground" and away from the defendant, he said.

How Florida's 'stand your ground' law 'spread like wildfires'

Since Florida enacted "stand your ground" in 2005, more than 22 states have adopted similar laws.

Roy Bedard, a use-of-force and defensive-tactics expert, explained why other states followed Florida's lead.

"It wasn't just Florida having these [crime] problems ... It seemed to be sensible to these other states," he said.

He added, "Other states wanted to see how it worked out in Florida, [and] it spread like wildfires across the U.S."

Everytown for Gun Safety, an independent organization working to reduce gun violence in the U.S., calls "stand your ground" laws "a threat to public safety."

"These laws encourage armed vigilantism by allowing a person to kill another person even when they can clearly and safely walk away from the danger and even in public areas," Everytown says on its website.

The rate of homicides, especially homicides by firearms, sharply increased in Florida after "stand your ground" was passed, according to a study published in November 2016 by The Journal of the American Medical Association Internal Medicine. The study's authors, however, acknowledged that multiple factors may have led to an increase in the Florida homicide rate.

"Circumstances unique to Florida may have contributed to our findings, including those that we could not identify," they wrote.

Baxley disputed the findings and argued that Americans should not be "panicking over" law-abiding citizens.

"They are not a threat to anybody and the firearm is not dangerous in the hands of that person," he said. "No one should be beaten, raped or murdered, robbed and feel like they couldn’t defend themselves or they might be in trouble."

'Stand your ground' in the spotlight

Before Reeves' hearing this week, there were two cases in particular that propelled Florida's self-defense laws onto the national stage: George Zimmerman, who was accused of fatally shooting 17-year-old Trayvon Martin, and Michael Dunn, who was accused of fatally shooting 17-year-old Jordan Davis at a Florida gas station in 2012.

Neither Zimmerman nor Dunn invoked the state's "stand your ground" law because "in both cases the defendants argued that deadly force was used because they reasonably believed that it was necessary to prevent imminent death or great bodily injury. That is, at its core, no different from the law in almost every other state," according to Dan Abrams, ABC News' legal analyst.

Zimmerman was acquitted of second-degree murder. Dunn was convicted of murder and sentenced to life in prison without the possibility of parole.

After the Zimmerman acquittal, then-Attorney General Eric Holder addressed the NAACP's annual convention, saying, "It's time to question laws that senselessly expand the concept of self-defense and sow dangerous conflict in our neighborhoods. These laws try to fix something that was never broken. There has always been a legal defense for using deadly force if — and the 'if' is important — no safe retreat is available."

The NRA responded with its own statement, vowing to "work to protect self-defense laws currently on the books and advocate for their passage in those states that do not fully respect this fundamental right."

One mother's path to advocacy

After Davis' death, his mother, Lucy McBath, felt compelled to learn more about Florida's "stand your ground" law.

"I can't just turn a blind eye because I received justice," she told ABC News.

McBath now serves as a spokesperson for Everytown for Gun Safety. She said she wants to stand up for "all the people across the country who do not have a voice, for people who are dying senselessly."

"'Stand your ground' laws give untrained citizens more leeway than the U.S. military gives our soldiers in war zones. There's something critically wrong with that," she said.

She added, "We have a responsibility, our legislatures have a responsibility ... to challenge these very laws that impinge on a person's civil, moral and ethical human right to live without the fear of being gunned down."

ABC News' Morgan Korn, Jeff Costello, Lindsey Jacobson, Julia Jacobo and Gillian Mohney contributed to this report.