Homicide rates rise after introduction of 'Stand Your Ground' self-defense law

The research, 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 (pop. 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.

The researchers examined publicly available data showing monthly totals of homicides -- in total and for firearm-related cases only -- for January 1999 to December 2014. Increases in homicide rates in Florida affected all the demographic groups examined, with the largest proportional rises in the 20-34 age group (which went up by 31%) and among the white population (which rose by 28%). A 20% increase was also found among African-Americans, says the paper.

The researchers considered a number of explanations: Firstly, they examined and found no significant changes in homicide rates with or without the involvement of guns in four US states that had not enacted a Stand Your Ground law over the same period of time (1999-2014) -- New York, New Jersey, Ohio and Virginia. Secondly, they tested whether the global recession of 2008-09 could have contributed to the observed rise in violence, examining outcomes known to be sensitive to economic shocks but unlikely to be affected by changes in self-defence laws. However, they found suicide rates in Florida between 2005 and 2014 did not rise significantly, so the research concludes that the recession was not the major factor associated with the rise in homicides in Florida.

Lead author Dr David Humphreys, Associate Professor of Evidence-Based Social Intervention and Policy at the University of Oxford, said: 'For some time, critics of Stand Your Ground laws have been concerned that laws extending the rights of citizens to use lethal force are likely to result in increased homicide and injury rates. Given Florida was the first state to extend the use of lethal force in this way, it is an important test case that many other states have since followed. Our study shows that the enactment of the law is linked with a sudden reversal in the decline in homicide rates and homicide rates have risen particularly where guns are involved. We hope these findings will inform the ongoing debates about the implications that Stand Your Ground laws may have for public safety in Florida and other US states.'

Co-author Dr Antonio Gasparrini at the London School of Hygiene & Tropical Medicine added: 'Stand Your Ground laws have been implemented across US states since 2005. Surprisingly, in spite of controversy surrounding guns and gun law in the US, very little research analysing its introduction has been conducted. This study highlights how Stand Your Ground is likely to be a cause of the rise in Florida murders, and provides crucial information which may influence future decision-making that affects wellbeing in the US and abroad.'

Dr Douglas Wiebe at the University of Pennsylvania, also a study co-author, commented: 'The findings are strong evidence that by extending the "no duty to retreat clause," this change to the law in Florida led to deaths that otherwise would not have occurred. We need to think about the implications of these findings and Florida should consider reversing this decision that appears to have increased the use of lethal force.'