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Evaluating the Impact of Florida's "Stand Your Ground" Self-defense Law on Homicide and Suicide by Firearm: An Interrupted Time Series Study.
JAMA Intern Med 2017; 177(1):44-50JIM

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.

Authors+Show Affiliations

Department of Social Policy and Intervention, University of Oxford, Oxford, United Kingdom2Green Templeton College, University of Oxford, Oxford, United Kingdom·.Department of Social & Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

27842169

Citation

Humphreys, David K., et al. "Evaluating the Impact of Florida's "Stand Your Ground" Self-defense Law On Homicide and Suicide By Firearm: an Interrupted Time Series Study." JAMA Internal Medicine, vol. 177, no. 1, 2017, pp. 44-50.
Humphreys DK, Gasparrini A, Wiebe DJ. Evaluating the Impact of Florida's "Stand Your Ground" Self-defense Law on Homicide and Suicide by Firearm: An Interrupted Time Series Study. JAMA Intern Med. 2017;177(1):44-50.
Humphreys, D. K., Gasparrini, A., & Wiebe, D. J. (2017). Evaluating the Impact of Florida's "Stand Your Ground" Self-defense Law on Homicide and Suicide by Firearm: An Interrupted Time Series Study. JAMA Internal Medicine, 177(1), pp. 44-50. doi:10.1001/jamainternmed.2016.6811.
Humphreys DK, Gasparrini A, Wiebe DJ. Evaluating the Impact of Florida's "Stand Your Ground" Self-defense Law On Homicide and Suicide By Firearm: an Interrupted Time Series Study. JAMA Intern Med. 2017 01 1;177(1):44-50. PubMed PMID: 27842169.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Evaluating the Impact of Florida's "Stand Your Ground" Self-defense Law on Homicide and Suicide by Firearm: An Interrupted Time Series Study. AU - Humphreys,David K, AU - Gasparrini,Antonio, AU - Wiebe,Douglas J, PY - 2016/11/15/pubmed PY - 2017/6/20/medline PY - 2016/11/15/entrez SP - 44 EP - 50 JF - JAMA internal medicine JO - JAMA Intern Med VL - 177 IS - 1 N2 - 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. SN - 2168-6114 UR - https://www.unboundmedicine.com/medline/citation/27842169/Evaluating_the_Impact_of_Florida's_"Stand_Your_Ground"_Self_defense_Law_on_Homicide_and_Suicide_by_Firearm:_An_Interrupted_Time_Series_Study_ L2 - https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/10.1001/jamainternmed.2016.6811 DB - PRIME DP - Unbound Medicine ER -