[Skip to Content]
Access to paid content on this site is currently suspended due to excessive activity being detected from your IP address 54.205.108.212. Please contact the publisher to request reinstatement.
[Skip to Content Landing]
Original Investigation
Firearm Violence
January 2017

Evaluating the Impact of Florida’s “Stand Your Ground” Self-defense Law on Homicide and Suicide by FirearmAn Interrupted Time Series Study

Author Affiliations
  • 1Department of Social Policy and Intervention, University of Oxford, Oxford, United Kingdom
  • 2Green Templeton College, University of Oxford, Oxford, United Kingdom·
  • 3Department of Social & Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
  • 4Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia
JAMA Intern Med. 2017;177(1):44-50. doi:10.1001/jamainternmed.2016.6811
Key Points

Question  Did the implementation of Florida’s “stand your ground” self-defense law have an impact on homicide and homicide by firearm between 2005 and 2014?

Findings  This study used an interrupted time series design to analyze changes in rates of homicide and firearm-related homicide. We found that the implementation of Florida’s stand your ground law was associated with a 24.4% increase in homicide and a 31.6% increase in firearm-related homicide.

Meaning  The removal of restrictions on when and where individuals can use lethal force was associated with a significant increase in homicide and homicide by firearm in Florida.

Abstract

Importance  In 2005, Florida amended its self-defense laws to provide legal immunity to individuals using lethal force in self-defense. The enactment of “stand your ground” laws in the United States has been controversial and their effect on rates of homicide and homicide by firearm is uncertain.

Objective  To estimate the impact of Florida’s stand your ground law on rates of homicide and homicide by firearm.

Design, Setting, and Participants  Using an interrupted time series design, we analyzed monthly rates of homicide and homicide by firearm in Florida between 1999 and 2014. Data were collected from the Wide-ranging Online Data for Epidemiologic Research (WONDER) web portal at the Centers for Disease Control and Prevention. We used seasonally adjusted segmented Poisson regression models to assess whether the onset of the law was associated with changes in the underlying trends for homicide and homicide by firearm in Florida. We also assessed the association using comparison states without stand your ground laws (New York, New Jersey, Ohio, and Virginia) and control outcomes (all suicides and suicides by firearm in Florida). October 1, 2005, the effective date of the law, was used to define homicides before and after the change.

Main Outcomes and Measures  Monthly rates of homicide, firearm-related homicide, suicide, and suicide by firearm in Florida and the 4 comparison states.

Results  Prior to the stand your ground law, the mean monthly homicide rate in Florida was 0.49 deaths per 100 000 (mean monthly count, 81.93), and the rate of homicide by firearm was 0.29 deaths per 100 000 (mean monthly count, 49.06). Both rates had an underlying trend of 0.1% decrease per month. After accounting for underlying trends, these results estimate that after the law took effect there was an abrupt and sustained increase in the monthly homicide rate of 24.4% (relative risk [RR], 1.24; 95%CI, 1.16-1.33) and in the rate of homicide by firearm of 31.6% (RR, 1.32; 95% CI, 1.21-1.44). No evidence of change was found in the analyses of comparison states for either homicide (RR, 1.06; 95% CI, 0.98-1.13) or homicide by firearm (RR, 1.08; 95% CI, 0.99-1.17). Furthermore, no changes were observed in control outcomes such as suicide (RR, 0.99; 95% CI, 0.94-1.05) and suicide by firearm (RR, 0.98; 95% CI, 0.91-1.06) in Florida between 2005 and 2014.

Conclusions and Relevance  The implementation of Florida’s stand your ground self-defense law was associated with a significant increase in homicides and homicides by firearm but no change in rates of suicide or suicide by firearm.

×