Firearm assaults against US law enforcement officers in the line-of-duty: Associations with firearm ownership and state firearm laws.

Law enforcement officers are disproportionately affected by occupational injury. Firearm violence is the second leading cause of occupational mortality for this group behind motor vehicle crashes. In the general population, greater firearm ownership and weaker firearm laws are associated with increased firearm violence incidence. It is plausible that a high prevalence of firearms could also be associated with a greater incidence of LEO assault with a firearm. Using data from the Federal Bureau of Investigation's, Uniform Crime Reporting, Police Employee Data for 2006-2016, we conducted a panel analysis to estimate the association between state-level estimates of household firearm ownership and LEO assault with a firearm. We additionally examined if effect modification by universal background check law status was present. Higher state-level firearm ownership was associated with an increased odds of LEO assault with a firearm in multi-level models. This association was modified by universal background check law status. In states without a universal background check law, for every 1% increase in state-level firearm ownership per agency-year, there was a 12.4% increase in the odds of an LEO assault with a firearm when adjusting for confounders (OR:1.124; 95% CI:1.018,1.240). In states with a universal background check law, there was no association. Findings, though small in magnitude, suggest aggregate firearm ownership may contribute to LEO assault with a firearm in states without a universal background check law. Future research to prevent LEO assault with a firearm should combine measures to address high rates of firearm ownership with other evidence-based prevention strategies.