Statement of Purpose Stand your ground (SYG) laws extend the right to use lethal force in self-defense. These laws have been controversial with media attention focusing on adolescent deaths – particularly Black adolescent deaths – including Trayvon Martin. Despite evidence that SYG law increase firearm homicides in adults, its impact on adolescents is unclear. We estimated the impact of Florida’s SYG law on adolescent firearm homicide and racial disparities.

Methods/Approach We used an interrupted time series analysis of quarterly firearm homicides rates of adolescents aged 15–19 years in Florida during 1999–2017. Micro-data files were obtained by special request from the CDC’s Restricted Use Vital Statistics. We used segmented quasi-Poisson regression to examine the impact of Florida’s SYG law, enacted in October 2005, on underlying trends in adolescent firearm homicides (ICD-10: X93-X95) and disaggregated by race (Black/White). We used a synthetic control (derived from comparison states without SYG laws) and negative control (firearm suicide) to address time-varying confounding.

Results Before Florida’s SYG law, the mean quarterly rate was 1.53 firearm homicides per 100,000 adolescents. There was no significant underlying trend. After adjusting for trends, the enactment of Florida’s SYG law was associated with a 44.6% significant increase in quarterly rates of adolescent firearm homicides (RR=1.45; 95% CI=1.17–1.79; p=0.0006). Black adolescents comprised 63.5% of all adolescent firearm homicides before and 71.8% after the law. No equivalent increases were seen in our synthetic control and negative control analyses.

Conclusions We found preliminary evidence that Florida’s SYG law is associated with an increase in adolescent firearm homicides and may also exacerbate racial disparities.

Significance and Contributions to Injury and Violence Prevention Science Determining the impacts of legalisation is key to identifying opportunities to reduce adolescent death by firearms and promote health equity.