The study published in JAMA Internal Medicine, led by the University of Oxford with the London School of Hygiene & Tropical Medicine and the University of Pennsylvania, looked at homicide rates before and after the enactment of State Bill 436, known as the Stand Your Ground law, which was signed by Governor Jeb Bush in 2005.
Before 2005, Florida's so-called 'Castle doctrine' allowed the use of lethal force in situations where individuals believed there was an imminent threat of death or serious physical harm from an intruder within their own home. The 2005 Bill extended the 'no duty to retreat' clause of the Castle doctrine, giving individuals immunity for using lethal force to defend themselves in public places, as well as on private property.
Prior to the introduction of the law, Florida (population 19.8 million) had on average 82 homicides per month, of which 49 deaths per month on average resulted from firearm-related injuries. The study says this change in the law is associated with homicide rates in Florida rising by 24% over 2005-2014 (compared with 1999-2004). Rates of homicide involving firearms specifically, went up even more – by 31%. Meanwhile, elsewhere in the United States, homicide rates in general have been declining since the 1990s, says the paper.