On the night of February 26, 2012 — three years ago today — police responded to several 911 calls from The Retreat at Twin Lakes, a gated community in Sanford, Florida. They arrived on the scene two minutes after George Zimmerman fatally shot teenager Trayvon Martin. Zimmerman told the officers he acted in self-defense, and police later said they had no reason to doubt him. Zimmerman was not arrested.

Under Florida's broad self-defense statute — commonly known as the "Stand Your Ground law" — the killing was perfectly legal. Zimmerman was eventually arrested and charged with murder, but a jury acquitted him of all charges in July 2013.

The Florida jury received specific instructions from the court that, as long as Zimmerman wasn't breaking the law prior to his encounter with Martin, he "had no duty to retreat and had the right to stand his ground and meet force with force." At least one juror said after the verdict was announced that Stand Your Ground was a key factor in the verdict.

Earlier this week, the Department of Justice officially closed their investigation into Martin's death, declining to pursue criminal civil rights charges against Zimmerman, who remains free despite a number of further run-ins with the law since the end of his trial.

Martin's death sparked massive protests and national conversations about race, racial profiling, and vigilantism that seemingly foreshadowed the events that followed the killing of Michael Brown in Ferguson, Missouri in August.

Stand Your Ground laws, meanwhile, are still in the books in 22 states. Legislators in at least 13 of those states tried to repeal or limit the statutes in the years since Martin's death, but only one — Louisiana — was successful. None of the states that were in the process of passing Stand Your Ground laws at the time of the killing have been able to do so.

Brina Milikowsky, chief strategy officer at Everytown for Gun Safety, a gun control advocacy group, told VICE News that the National Rifle Association (NRA) and the American Legislative Exchange Council (ALEC) lobbied aggressively for the laws in the years prior to Zimmerman's deadly encounter with Martin.

"Florida is the most extreme example and was the original brainchild of an NRA lobbyist there, and that version of the law was then exported out across different states," Milikowsky said. "The fact that the gun lobby has pushed Stand Your Ground laws and is trying to upend centuries of self defense laws can be seen as part of their larger agenda to push the presence of guns in everyday life, and either weaken or dismantle the existing public safety standard about responsible gun ownership."

But the controversy surrounding the Martin-Zimmerman case expanded public awareness about the laws, as did several studies that highlighted their devastating impact, particularly on black and Hispanic communities.

Essentially, Stand Your Ground laws say that people are not required to retreat from conflict, even when they are safely able to do so. In many states, the rule only applies to a person's car or house — an extension of the so-called "Castle Doctrine," which allows citizens to protect their private property with deadly force. But in Florida — where a particularly extreme version was signed into law by then Governor Jeb Bush in 2005 — that concept also extends to public spaces.

Critics say Florida's statute promotes vigilantism and basically encourages people to escalate conflicts that could otherwise be avoided.

"Even in public areas like parking lots and playgrounds, where there are a lot of other people around and you have the ability to safely retreat instead of engaging in violence, you are given a free pass to commit a lethal act," Milikowsky said.

Researchers found that Stand Your Ground laws are associated with a clear increase in homicides — as many as 700 more per year. They also found that the rate of "justifiable" homicides doubled — climbing 53 percent — in states that passed the laws while it slightly declined elsewhere, Milikowsky said.

A 2013 study by the Urban Institute looked at the disproportionate impact of Stand Your Ground laws on communities of color. They found that in cases with a white shooter and a black victim, the killing was 11 times more likely to be ruled "justifiable" than when the races were reversed.

"The conversation that came out of Trayvon's murder has changed some legislators' approach to these bills," Milikowsky said. "The ones that have common sense have stopped these bills in their tracks and are now voting against other efforts to expand Stand Your Ground."

But while Martin's death may have halted Stand Your Ground laws from spreading across the country, it has not led to their repeal.

Black Lives Matter

The blurred line between self-defense and escalation, instead, has been at the heart of a slew of new cases involving not only private citizens — self-appointed neighborhood watch guards like Zimmerman — but also police officers.

Dante Barry, a grassroots organizer with Million Hoodies, a racial justice group that takes its name from the hooded sweatshirt Martin was wearing when he was killed, told VICE News that he believes the country needs to have "a deep conversation" about public safety and self-defense in the aftermath of the events in Ferguson.

"We need to reframe the conversation to ask, what does public safety mean for communities of color?" Barry said. "Who has the right to claim what self defense looks like? When we say 'black lives matter,' it's not just a chant, it's not just a mantra, it's a political demand. But we are also challenging folks to answer this question: What does our community, our country look like when black lives matter?"

Barry noted that there is often a disconnect between racial justice groups like his Million Hoodies organization and the gun control movement, which has largely been fueled by school shootings — like the massacre at Sandy Hook Elementary School in December 2012 — which tend to impact a different demographic.

Both affluent suburbs and urban communities have been affected by gun violence, but only communities of color that have experienced the criminalization of youth that leads to the so-called "school to prison pipeline," Barry noted.

"The response to these shootings has been to put more police in our schools, bars on public school windows, metal detectors," Barry said. "It really creates this prison-like culture that perpetuates and tells people at a young age, 'You're going to go into this prison-like culture for the rest of your life.'"

Martin's killing may have struck a chord with groups lobbying for both racial equality and gun control, but different approaches to the issues largely failed to unify the two movements.

Trayvon Martin vs. Marissa Alexander

While Martin's killing illustrated how Florida's Stand Your Ground law could give individuals involved in violent confrontations the benefit of the doubt in court, the case of a young, black Florida mother, Marissa Alexander, showed the law is not always applied equally.

In July 2010, Alexander fired a single shot during a dispute with her estranged husband. No one was injured or killed. Alexander always maintained she had fired a "warning shot" after her husband had attacked and threatened to kill her. In other words, she claimed that she had "stood her ground."

Florida State Attorney Angela Corey — the same prosecutor in Zimmerman's trial — was the one pressing charges against Alexander. But the similarities between the two cases end there.

Unlike Zimmerman, Alexander, who had no prior criminal record or arrests, was immediately arrested at the scene of the shooting. It only took a jury 12 minutes of deliberation to find her guilty. Because of Florida's "10-20-life" mandatory minimum sentencing law, she was sentenced to 20 years in prison in May 2012.

Supporters advocated tirelessly for her release, however, and she was re-sentenced last month to house arrest — after spending three years behind bars.

"Certainly there is an uneven application of this law, and arguably the application of a lot of laws," Milikowsky said. "But because Stand Your Ground laws are so subjective, they remove the core tenets of self-defense law, and that has left more room for confusion about when and where self-defense principles apply."

When Alexander was sentenced, much of the debate focused on whether Stand Your Ground was applied discriminatorily. But some critics of the law felt that using the law in her defense would legitimize it — when they wanted it repealed.

"It wasn't her fault that her lawyers thought that was the best way to win her case," Aleta Alston Toure, a lead organizer of the group Free Marissa Now, told VICE News. "These cases were used against each other, meaning, some couldn't support Free Marissa Now because they were trying to get rid of Stand Your Ground."

Toure' and others focused their advocacy in Alexander's case on Florida's mandatory minimum sentencing law. But they also joined Martin's mother Sybrina Fulton, and the father of Jordan Davis, a black teen killed in November 2012 over a loud music dispute at a Jacksonville gas station, to testify against Stand Your Ground laws at a UN special hearing in Washington, DC.

"Marissa's lawyers were gonna utilize Stand Your Ground in court, but the others with us were all together to get rid of Stand Your Ground," Toure' said. "Stand Your Ground is not as important to Marissa, it's the 10-20 [years] to life that's important. Her life, the life of her children, depended on the 10-20."

Toure' said the disagreement on strategy in Alexander's case was reflective of larger issues that surround gun control and Stand Your Ground, as well as racial and gender biases.

"The politics divided us in the struggle," she said.