Mass homicide by firearm in Canada: Effects of legislation
Abstract
Canada implemented a series of laws regulating firearms including background checks and licensing, references, psychological questionnaires, prohibition of paramilitary style rifles, and magazine capacity restrictions in order to decrease the incidences and deaths from mass shootings. The associated effects of these laws were examined over the years 1974 to 2020. A model was constructed using difference-in-differences analysis of firearms and non-firearms mass homicide incidences and death rates. Mass homicides were defined as a homicide due to one event involving three or more deaths. Incidence rates of mass homicide by firearm were found to be 0.11 (95%CI 0.08, 0.14) per million compared to a non-firearm mass homicide rate of 0.12 (95% CI 0.10, 0.15) per million. Mass homicide death rates by firearm were found to be 0.39 (95% CI 0.29, 0.49) per million compared to a non-firearm mass homicide rate of 0.47 (95% CI 0.34, 0.61) per million. Overall, there is a gradual declining trend in the incidence of mass homicide by firearm (IRR 0.97 (95% CI 0.96, 0.98)) and by non-firearm (IRR 0.97 (95% CI 0.97, 0.98)). The decline in mass homicide death rate by firearm and non-firearm is IRR 0.96 (95% CI 0.95, 0.97), and IRR 0.97 (95% CI 0.96, 0.98) respectively. No specific associated decrease in mass homicide incidence rates or death rates with firearms legislation was found after the implementation of background checks and prohibition of full auto firearms in 1980, by the implementation of references and psychological questionnaires in 1994, by the restriction of magazine capacity in 1994, the prohibition of paramilitary rifles in 1994, or licensing in 2001.
Conclusions
This is the first study to examine mass homicide in Canada as well as the association between legislative interventions controlling firearms and firearm mass homicide incidence rates and deaths. Over the period 1974 to 2020 the incidence and death rates associated with mass homicide gradually declined. Interestingly, interventions such as background checks, licensing, prohibition of military style firearms, and prohibiting large-capacity magazines, were not specifically associated with changes in the incidence and deaths by mass homicide by firearms. The benefit from the consistency of firearms regulations in Canada eliminates the confounders in US studies due to the differing regulations across states. Recommended areas for data collection by Statistics Canada to aid future study include locations of incidents, the interpersonal relationship between perpetrator and victim, and the perpetrator’s motivation for mass homicide.
journals.plos.org/plosone/article?id=10.1371/journal.pone.0266579#sec009