In a police video from the night Trayvon Martin was shot and killed, George Zimmerman does not appear to be wounded. (Screenshot: ABC News.)

In perhaps the most famous “Stand Your Ground” case, George Zimmerman, shown here after his arrest, shot and killed teenager Trayvon Martin. (Screenshot: ABC News.)

By Ashley Lopez
Florida Center for Investigative Reporting

A new study found that states with so-called “Stand Your Ground” laws have higher homicide rates.

These laws — which permit people to use lethal force to defend themselves in public — have passed in nearly two dozen states already and were enacted in Florida in 2005. Typically, people are only allowed to use lethal force in their homes for self-defense. However, these laws allow people to fire a gun in parks and out in the street if they feel threatened.

Florida’s law, in particular, garnered national attention after the controversial shooting of 17-year-old Trayvon Martin last year.

Gun rights advocates have strongly supported the law, but others have claimed the law leads to possible vigilantes like George Zimmerman, who shot Martin in what he claims was an effort to stand his ground. There remains dispute as to whether the law was properly applied in this case and whether such laws are necessary in the first place.

A new study, however, looks specifically at states that have passed these laws and how homicide rates in those states have changed.

According to NPR:

Researchers who’ve studied the effect of the laws have found that states with a stand your ground law have more homicides than states without such laws.

“These laws lower the cost of using lethal force,” says Mark Hoekstra, an economist with Texas A&M University who examined stand your ground laws. “Our study finds that, as a result, you get more of it.” …

Hoekstra recently decided to analyze national crime statistics to see what happens in states that pass stand your ground laws. He found the laws are having a measurable effect on the homicide rate.

“Our study finds that, that homicides go up by 7 to 9 percent in states that pass the laws, relative to states that didn’t pass the laws over the same time period,” he says.

As to whether the laws reduce crime — by creating a deterrence for criminals — he says, “we find no evidence of any deterrence effect over that same time period.”

Hoekstra obtained this result by comparing the homicide rate in states before and after they passed the laws. He also compared states with the laws to states without the laws.

Because the study didn’t necessarily find an increase in “justified killings” or in criminals using weapons, researchers think that the cause for this spike in homicide rates might be that “Stand Your Ground” laws up the ante in other altercations.

“One possibility for the increase in homicide is that perhaps [in cases where] there would have been a fistfight … now, because of stand your ground laws, it’s possible that those escalate into something much more violent and lethal,” Hoekstra tells NPR.

Florida’s law passed at the behest of special interests, including the National Rifle Association and the American Legislative Exchange Council.

In Florida, more than 1 million people have obtained firearm permits as of early this month. That’s more than in any other state in the country.