Florida’s controversial “stand your ground” law, which allows people to use deadly force if they’re acting in self-defense, has led to a significant rise in killings, according to a new medical study.

The law, implemented in 2005, was associated with a 32 percent rise in firearm-related homicides in Florida and a nearly 25 percent rise in killings overall in the state, according to the study published in the Journal of the American Medical Association.

Researchers examined the number of homicides per month between 1999 and 2014 and found that “after the law took effect, there was an abrupt and sustained increase.”

The “stand your ground” law allows for “justifiable use of force” against others if the person has a presumption of imminent danger or death, either within his/her own home or in public. Supporters of the law say it is necessary to protect people from violent crime if they feel threatened. The law was passed in Florida after a sustained lobbying campaign from the National Rifle Association.

But opponents, who call it the “shoot first” law, argue that it merely allows people to shoot others and then claim self-defense later. According to a 2010 investigation by the St. Petersburg Times, justifiable homicides tripled in the years since the “stand your ground” law was implemented.

The laws are also controversial due to race. Research shows that the “stand your ground” defense is significantly more successful when invoked by whites against blacks than the other way around.

“Stand your ground” laws, also called “castle doctrine” laws, change how people weigh the decision of using deadly force. These laws “expand the legal justification for the use of lethal force in self-defense, thereby lowering the expected cost of using lethal force and increasing the expected cost of committing violent crime,” researchers at Texas A&M found in a 2013 study.

The “stand your ground” defense was famously invoked by George Zimmerman in the shooting death of the unarmed black teen Trayvon Martin in February 2012. Martin was walking back to a family member’s home at night in Sanford, Florida, when Zimmerman spotted him, deemed him suspicious, and fatally shot him. Zimmerman was charged with murder but got off after he said he was acting in self-defense.

Florida was the first state to pass a stand your ground law, and it was quickly followed by about 30 other states passing similar measures.