Importance

Rapid-fire weapons are often used by perpetrators in mass shooting incidents. In 1996 Australia introduced major gun law reforms that included a ban on semiautomatic rifles and pump-action shotguns and rifles and also initiated a program for buyback of firearms.

Objective

To determine whether enactment of the 1996 gun laws and buyback program were followed by changes in the incidence of mass firearm homicides and total firearm deaths.

Design

Observational study using Australian government statistics on deaths caused by firearms (1979-2013) and news reports of mass shootings in Australia (1979–May 2016). Changes in intentional firearm death rates were analyzed with negative binomial regression, and data on firearm-related mass killings were compared.

Exposures

Implementation of major national gun law reforms.

Main Outcomes and Measures

Changes in mass fatal shooting incidents (defined as ≥5 victims, not including the perpetrator) and in trends of rates of total firearm deaths, firearm homicides and suicides, and total homicides and suicides per 100 000 population.

Results

From 1979-1996 (before gun law reforms), 13 fatal mass shootings occurred in Australia, whereas from 1997 through May 2016 (after gun law reforms), no fatal mass shootings occurred. There was also significant change in the preexisting downward trends for rates of total firearm deaths prior to vs after gun law reform. From 1979-1996, the mean rate of total firearm deaths was 3.6 (95% CI, 3.3-3.9) per 100 000 population (average decline of 3% per year; annual trend, 0.970; 95% CI, 0.963-0.976), whereas from 1997-2013 (after gun law reforms), the mean rate of total firearm deaths was 1.2 (95% CI, 1.0-1.4) per 100 000 population (average decline of 4.9% per year; annual trend, 0.951; 95% CI, 0.940-0.962), with a ratio of trends in annual death rates of 0.981 (95% CI, 0.968-0.993). There was a statistically significant acceleration in the preexisting downward trend for firearm suicide (ratio of trends, 0.981; 95% CI, 0.970-0.993), but this was not statistically significant for firearm homicide (ratio of trends, 0.975; 95% CI, 0.949-1.001). From 1979-1996, the mean annual rate of total nonfirearm suicide and homicide deaths was 10.6 (95% CI, 10.0-11.2) per 100 000 population (average increase of 2.1% per year; annual trend, 1.021; 95% CI, 1.016-1.026), whereas from 1997-2013, the mean annual rate was 11.8 (95% CI, 11.3-12.3) per 100 000 (average decline of 1.4% per year; annual trend, 0.986; 95% CI, 0.980-0.993), with a ratio of trends of 0.966 (95% CI, 0.958-0.973). There was no evidence of substitution of other lethal methods for suicides or homicides.

Conclusions and Relevance

Following enactment of gun law reforms in Australia in 1996, there were no mass firearm killings through May 2016. There was a more rapid decline in firearm deaths between 1997 and 2013 compared with before 1997 but also a decline in total nonfirearm suicide and homicide deaths of a greater magnitude. Because of this, it is not possible to determine whether the change in firearm deaths can be attributed to the gun law reforms.