The Effect of Large-Capacity Magazine Bans on High-Fatality Mass Shootings, 1990-2017

How firearm legislation impacts firearm mortality internationally: A scoping review

Background

The literature on gun violence is broad and variable, describing multiple legislation types and outcomes in observational studies. Our objective was to document the extent and nature of evidence on the impact of firearm legislation on mortality from firearm violence.

Methods

A scoping review was conducted under PRISMA-ScR guidance. A comprehensive peer-reviewed search strategy was executed in several electronic databases from inception to March 2024. Grey literature was searched for unpublished sources. Data were extracted on study design, country, population, type of legislation, and overall study conclusions on legislation impact on mortality from suicide, homicide, femicide, and domestic violence. Critical appraisal for a sample of articles with the same study design (ecological studies) was conducted for quality assessment.

Findings

5057 titles and abstracts and 651 full-text articles were reviewed. Following full-text review and grey literature search, 202 articles satisfied our eligibility criteria. Federal legislation was identified from all included countries, while state-specific laws were only reported in studies from the U.S. Numerous legislative approaches were identified including preventative, prohibitive, and more tailored strategies focused on identifying high risk individuals. Law types had various effects on rates of firearm homicide, suicide, and femicide. Lack of robust design, uneven implementation, and poor evaluation of legislation may contribute to these differences.

Interpretation

We found that national, restrictive laws reduce population-level firearm mortality. These findings can inform policy makers, public health researchers, and governments when designing and implementing legislation to reduce injury and death from firearms.

Funding

Funding is provided by the Strategy for Patient-Oriented Research (SPOR) Evidence Alliance and in part by St. Michael's Hospital, University of Toronto.

Scoping review registration

Open Science Framework (OSF): https://osf.io/sf38n.

Public Mass Shootings: Counterfactual Trend Analysis of the Federal Assault Weapons Ban

Background

Assault weapon and large-capacity magazine bans are potential tools for policy makers to prevent public mass shootings. However, the efficacy of these bans is a continual source of debate. In an earlier study, we estimated the impact of the Federal Assault Weapons Ban (FAWB) on the number of public mass shooting events in the United States. This study provides an updated assessment with 3 additional years of firearm surveillance data to characterize the longer-term effects.

Objective

This study aims to estimate the impact of the FAWB on trends in public mass shootings from 1966 to 2022.

Methods

We used linear regression to estimate the impact of the FAWB on the 4-year simple moving average of annual public mass shootings, defined by events with 4 or more deaths in 24 hours, not including the perpetrator. The study period spans 1966 to 2022. The model includes indicator variables for both the FAWB period (1995-2004) and the period after its removal (2005-2022). These indicators were interacted with a linear time trend. Estimates were controlled for the national homicide rate. After estimation, the model provided counterfactual estimates of public mass shootings if the FAWB was never imposed and if the FAWB remained in place.

Results

The overall upward trajectory in the number of public mass shootings substantially fell while the FAWB was in place. These trends are specific to events in which the perpetrator used an assault weapon or large-capacity magazine. Point estimates suggest the FAWB prevented up to 5 public mass shootings while the ban was active. A continuation of the FAWB and large-capacity magazine ban would have prevented up to 38 public mass shootings, but the CIs become wider as time moves further away from the period of the FAWB.

Conclusions

The FAWB, which included a ban on large-capacity magazines, was associated with fewer public mass shooting events, fatalities, and nonfatal gun injuries. Gun control legislation is an important public health tool in the prevention of public mass shootings.

State assault weapons bans are associated with fewer fatalities: analysis of US county mass shooting incidents (2014-2022)

BACKGROUND

The need for evidence to inform interventions to prevent mass shootings (MS) in the USA has never been greater.

METHODS

Data were abstracted from the Gun Violence Archive, an independent online database of US gun violence incidents. Descriptive analyses consisted of individual-level epidemiology of victims, suspected shooters and weapons involved, trends and county-level choropleths of population-level incident and fatality rates. Counties with and without state-level assault weapons bans (AWB) were compared, and we conducted a multivariable negative binomial model controlling for county-level social fragmentation, median age and number of gun-related homicides for the association of state-level AWB with aggregate county MS fatalities.

RESULTS

73.3% (95% CI 72.1 to 74.5) of victims and 97.2% (95% CI 96.3 to 98.3) of shooters were males. When compared with incidents involving weapons labelled 'handguns', those involving a weapon labelled AR-15 or AK-47 were six times more likely to be associated with case-fatality rates greater than the median (OR=6.1, 95% CI 2.3 to 15.8, p<0.00001). MS incidents were significantly more likely to occur on weekends and during summer months. US counties in states without AWB had consistently higher MS rates throughout the study period (p<0.0001), and the slope for increase over time was significantly lower in counties with AWB (beta=-0.11, p=0.01). In a multivariable negative binomial model, counties in states with AWB were associated with a 41% lower incidence of MS fatalities (OR=0.58, 95% CI 0.37 to 0.97, p=0.02).

CONCLUSIONS

Counties located in states with AWB were associated with fewer MS fatalities between 2014 and 2022.

Nearly 20 Years Since the Federal Ban: Can State-Level Assault Weapon Prohibitions Fill the Void? Comparative Analysis of Case Fatality and Assault Weapon Recovery in States With and Without an Assault Weapon Ban

INTRODUCTION

Few states established assault weapon bans (AWBs) after the federal AWB expired. The effectiveness of state AWBs as well as neighboring state legislation, in reducing the local prevalence of assault weapons (AWs) or in reducing overall shooting lethality is unknown.

METHODS

We queried the Gun Violence Archive (2014-2021) to identify US firearm injuries and fatalities. Shooting case fatality rates were compared among states with and without AWBs, as reported in the State Firearm Laws Database. Data on recovered firearms was obtained from the ATF Firearms Trace Database and used to estimate weapon prevalence. Recovered firearms were classified as AWs based on caliber (7.62 mm, 5.56 mm, 0.223 cal). We performed spatially weighted linear regression models, with fixed effects for state and year to assess the association between geographically clustered state legislation and firearm outcomes.

RESULTS

From 2014 to 2021, the US shooting victim case fatality rate was 8.06% and did not differ among states with and without AWBs. The proportion of AWs to total firearms was 5.0% in states without an AWB and 6.0% in states with an AWB (mean difference [95% CI] = -0.8% [-1.6% to -0.2%], P = 0.03). Most recovered firearms in AWB states originated from non-AWB states. On adjusted models, there was no association between state-level AWB and firearm case fatality; however, adjacency to states with an AWB was associated with lower case fatality (P < 0.001). Clustered AWB states with shared borders had lower AW prevalence and fatality rates than the rest of the US.

CONCLUSIONS

Isolated state AWBs are not inversely associated with shooting case fatality rates nor the prevalence of AWs, but AWBs among multiple neighboring states may be associated with both outcomes.

Epidemiology of Mass Shootings in the United States

This in-depth review delves into the multifaceted realm of mass shootings and explores their epidemiology from a psychological perspective. The article presents a comprehensive examination of the prevalence, perpetrator and victim profiles, motives, and contributing factors associated with mass shootings. By investigating the intricate relationship between masculinity, domestic violence, military service, social media, fame-seeking, suicidal ideation, mental illness, and firearms, this article sheds light on the multifaceted nature of mass shootings. Moreover, it discusses the importance of implementing effective prevention strategies to address this growing public health concern. The findings from this review serve as a valuable resource for researchers, practitioners, policy makers, and the community at large, facilitating a deeper understanding of mass shootings and fostering the development of evidence-based solutions to prevent these tragic incidents.

The Views of Police Officers Toward Gun Legislation and Public Health Policies Driven by Firearm Safety Concerns

Gun violence is a principal cause of premature death in America. It has been suggested that solutions to gun violence may be found using a public health approach, which is broader than dealing with the problem via law enforcement alone. A component of a public health approach to gun violence is the implementation of policies or laws. Unfortunately, there is a serious gap in our understanding of how street-level police officers view proposed or existing firearms legislation. This is an important omission, because it is line-level personnel who are tasked with enforcing these policies within highly discretionary contexts. We surveyed police from three jurisdictions to establish a baseline understanding of officers' views about potential gun legislation and identify possible resistance and implementation barriers of firearms laws. The findings suggest that those responsible for enforcing new laws show limited or mixed support for the same. Officers were most supportive of laws that increase the presence of trained gun owners within certain contexts and ensure that individuals with criminal backgrounds or mental health concerns do not have access to firearms. Most officers support prohibiting gun ownership following conviction of a domestic violence offense. However, officers generally opposed gun legislation banning assault weapons, large capacity magazines, and internet ammunition purchases. Finally, officers with the Buffalo Police Department-which recently had experienced an active-shooter event-were more supportive of almost all types of legislation. Respondents expressing greater concern about officer safety related to firearms were supportive of several types of firearm legislation.

Increasing Injury Intensity among 6,500 Violent Deaths in the State of Maryland

BACKGROUND

Anecdotal evidence strongly suggests there has been a rise in violent crimes. This study sought to examine trends in injury characteristics of homicide victims in Maryland. We hypothesized that there would be an increase in the severity of wound characteristics.

STUDY DESIGN

The Office of the Chief Medical Examiner is a statewide agency designated by law to investigate all homicides, suicides, or unusual or suspicious circumstances. Using individual autopsy reports, we collected data among all homicides from 2005 to 2017, categorizing them into 3 time periods: 2005 to 2008 (early), 2009 to 2013 (mid), and 2014 to 2017 (late). Primary outcomes included the number of gunshots, stabs, and fractures from assaults. High-violence intensity outcomes included victims having 10 or more gunshots, 5 or more stabs, or 5 or more fractures from assaults.

RESULTS

Of 6,500 homicides (annual range 403 to 589), the majority were from firearms (75%), followed by stabbings (14%) and blunt assaults (10%). Most homicide victims died in the hospital (60%). The average number of gunshots per victim was 3.9 (range 1 to 54), stabs per victim was 9.4 (range 1 to 563), and fractures from assaults per victim was 3.7 (range 0 to 31). The proportion of firearm victims with at least 10 gunshots nearly doubled from 5.7% in the early period to 10% (p < 0.01) in the late period. Similarly, the proportion with 5 or more stabbings increased from 39% to 50% (p = 0.02) and assault homicides with 5 or more fractures increased from 24% to 38% (p < 0.01).

CONCLUSIONS

In Maryland, the intensity of violence increased across all major mechanisms of homicide. Further follow-up studies are needed to elucidate the root causes underlying this escalating trend.

HIV Criminalization Laws and Enforcement: Assessing the Relationship Between HIV Criminalization at the State Level, Policing at the County Level, and County-level HIV Incidence Rates

The U.S. HIV epidemic disproportionately affects Black and Hispanic communities via ecosocial determinants of excess HIV risk, including HIV criminalization laws and overpolicing. This study used multilevel modeling to test the hypothesis that HIV criminalization laws are associated with higher county HIV incidence, and that this effect is modified by heavier county-level policing. County-level HIV incidence data from 2010 to 2019 were merged with county-level demographic, socioeconomic, and jailed population rate data for counties with stable HIV incidence rates (rates generated from a numerator of at least 12) for > 5 years. Multivariable multilevel (hierarchical) models for count-rate data were fitted, with years nested inside counties, and counties nested within states. An HIV criminalization law was associated with higher countywide HIV incidence rate for the general, Black, and Hispanic populations (aRR = 1.14, 1.30, and 1.32, respectively). This association was modified by an increased county jailed population rate for the general and Black populations.

Analyzing the impact of state gun laws on mass shootings in the United States from 2013 to 2021

OBJECTIVES

Mass shooting incidents have drastically increased in the United States in the last 10 years, with a disproportionate number of incidents occurring in some states. Gun laws vary greatly by state, but little research has been conducted to examine the association between the strength of state gun laws and mass shootings. This study aims to explore the aggregate effect of state gun laws on the rate of mass shooting incidents and fatalities.

STUDY DESIGN

This was a cross-sectional time series.

METHODS

This study applied the negative binomial generalized linear mixed model to assess the impact of state gun laws restrictiveness-as measured by the total number of active gun laws-on the rate of mass shooting incidents and fatalities.

RESULTS

The restrictiveness of state gun laws was significantly associated with the rate of mass shooting fatalities; specifically, for every 1 standard deviation (SD) increase in the state gun law restrictiveness score (i.e. for every additional 27 gun laws in place), the rate of mass shooting fatalities was decreased by 24% (P-value <0.0001), controlling for other predictor variables in the model. However, no significant association was found between the restrictiveness of state gun laws and rate of mass shooting incidents.

CONCLUSIONS

State gun laws may not decrease the number of mass shooting events, but they appear to help reduce the number of deaths when these mass shootings occur. Better data collection on mass shootings and further research on the impacts of specific gun laws are needed to help understand the effectiveness of gun laws and inform law-based interventions.

Gun violence in K-12 schools in the United States: Moving towards a preventive (versus reactive) framework

Intentional shootings in K-12 schools in the U.S. persist as a public health problem. The number of shootings in K-12 schools has increased precipitously since 2017. And with approximately 100,000 K-12 public schools nationally serving 51 million children, investing in a comprehensive gun violence prevention strategy is critical. Unfortunately, our current school gun violence prevention approach almost exclusively centers reactive strategies that are in place to respond to acts of gun violence in the moment, rather than preventive strategies that would prevent them from occurring at all. Reliance on these strategies alone, however, is not sufficient. In line with the core tenets of public health prevention and the Whole School, Whole Child, Whole Community model, we present a more expansive school gun violence prevention framework that broadens the spectrum of what constitutes "school gun violence prevention." Our work highlights how enhancing basic neighborhood and school structures-including investments in public libraries, affordable housing, and universal school-based violence prevention programs-are key to both preventing gun violence and promoting well-being. We also highlight the role of stricter gun laws, reasonable school security efforts, bystander interventions, building awareness within school communities, and meaningful investments in early interventions and mental health services. Children, who have been tragically exposed to any number of adverse experiences in the wake of the COVID-19 pandemic, deserve more reasoned choices and large-scale investments in understanding and cutting off the root causes of school gun violence; not just a reliance on strategies that focus on what to do in the moment of a violent act. As gun violence in K-12 schools persists, we must reframe the discourse about school gun violence around prevention, not reaction.

Firearm-Related Injuries and Deaths in Children and Youth

Firearms are the leading cause of death in children and youth 0 to 24 years of age in the United States. In 2020, firearms resulted in 10,197 deaths (fatality rate 9.91/100,000 youth 0-24 years old). Firearms are the leading mechanism of death in pediatric suicides and homicides. Increased access to firearms is associated with increased rates of firearm deaths. Substantial disparities in firearm injuries and deaths exist by age, gender, race, ethnicity, and sexual orientation and gender identity and for deaths related to legal intervention. Barriers to firearm access can decrease the risk to youth for firearm suicide, homicide, or unintentional shooting injury and death. Given the high lethality of firearms and the impulsivity associated with suicidal ideation, removing firearms from the home or securely storing them-referred to as lethal means restriction of firearms-is critical, especially for youth at risk for suicide. Primary care-, emergency department-, mental health-, hospital-, and community-based intervention programs can effectively screen and intervene for individuals at risk for harming themselves or others. The delivery of anticipatory guidance coupled with safety equipment provision improves firearm safer storage. Strong state-level firearm legislation is associated with decreased rates of firearm injuries and death. This includes legislation focused on comprehensive firearm licensing strategies and extreme risk protection order laws. A firm commitment to confront this public health crisis with a multipronged approach engaging all stakeholders, including individuals, families, clinicians, health systems, communities, public health advocates, firearm owners and nonowners, and policy makers, is essential to address the worsening firearm crisis facing US youth today.

Reducing Firearm Injury and Death in the United States

Firearms injury is a major cause of American morbidity and mortality. Although the firearm is a common vector, the intentions with which it is used represent a wide array of social ills-suicide, community violence, domestic violence, mass shootings, legal intervention, and unintended injury. The political and social underpinnings of this epidemic are inseparable from its prevention measures. Surgeons have an important role in firearm policy, research, prehospital and hospital advances, trauma survivor networks, and hospital-based violence prevention programs. It is only through interdisciplinary, multilevel, evidence-based prevention measures that the tides will turn on American firearm injury.

US Mass public shootings since Columbine: victims per incident by race and ethnicity of the perpetrator

White individuals in the United States (US) have historically had disproportionate access to firearms. The real-life availability of firearms, including those most lethal, may still be greater among White populations, manifesting in the number of victims in shootings. We compared the severity of US mass public shootings since Columbine by race and/or ethnicity of the perpetrator using The Violence Project Database of Mass Shooters, assessing fatalities (minimum four), total victims, type, and legal status of guns used. We used data visualization and Quasi-Poisson regression of victims minus four - accounting for truncation at 4 fatalities - to assess fatality and total victim rates comparing Non-Hispanic (NH) White with NH Black shooters, using winsorization to account for outlier bias from the 2017 Las Vegas shooting. In 104 total mass public shootings until summer 2021, NH White shooters had higher median fatalities (6 [IQR 5-9] versus 5 [IQR 4-6]) and total victims (9 [IQR 6-19] versus 7 [IQR 5-12]) per incident. Confidence intervals of NH Black versus NH White fatalities rate ratios (RR) ranged from 0.17-1.15, and of total victim RRs from 0.15-1.04. White shooters were overrepresented in mass public shootings with the most victims, typically involving legally owned assault rifles. To better understand the consequences when firearms are readily available, including assault rifles, we need a database of all US gun violence. Our assessment of total victims beyond fatalities emphasizes the large number of US gun violence survivors and the need to understand their experiences to capture the full impact of gun violence.

The Revolution Will Be Hard to Evaluate: How Co-Occurring Policy Changes Affect Research on the Health Effects of Social Policies

Extensive empirical health research leverages variation in the timing and location of policy changes as quasi-experiments. Multiple social policies may be adopted simultaneously in the same locations, creating co-occurrence that must be addressed analytically for valid inferences. The pervasiveness and consequences of co-occurring policies have received limited attention. We analyzed a systematic sample of 13 social policy databases covering diverse domains including poverty, paid family leave, and tobacco use. We quantified policy co-occurrence in each database as the fraction of variation in each policy measure across different jurisdictions and times that could be explained by covariation with other policies. We used simulations to estimate the ratio of the variance of effect estimates under the observed policy co-occurrence to variance if policies were independent. Policy co-occurrence ranged from very high for state-level cannabis policies to low for country-level sexual minority-rights policies. For 65% of policies, greater than 90% of the place-time variation was explained by other policies. Policy co-occurrence increased the variance of effect estimates by a median of 57-fold. Co-occurring policies are common and pose a major methodological challenge to rigorously evaluating health effects of individual social policies. When uncontrolled, co-occurring policies confound one another, and when controlled, resulting positivity violations may substantially inflate the variance of estimated effects. Tools to enhance validity and precision for evaluating co-occurring policies are needed.

What to Do When Everything Happens at Once: Analytic Approaches to Estimate the Health Effects of Co-Occurring Social Policies

Social policies have great potential to improve population health and reduce health disparities. Increasingly, those doing empirical research have sought to quantify the health effects of social policies by exploiting variation in the timing of policy changes across places. Multiple social policies are often adopted simultaneously or in close succession in the same locations, creating co-occurrence that must be handled analytically for valid inferences. Although this is a substantial methodological challenge for researchers aiming to isolate social policy effects, only in a limited number of studies have researchers systematically considered analytic solutions within a causal framework or assessed whether these solutions are being adopted. We designated 7 analytic solutions to policy co-occurrence, including efforts to disentangle individual policy effects and efforts to estimate the combined effects of co-occurring policies. We used an existing systematic review of social policies and health to evaluate how often policy co-occurrence is identified as a threat to validity and how often each analytic solution is applied in practice. Of the 55 studies, only in 17 (31%) did authors report checking for any co-occurring policies, although in 36 studies (67%), at least 1 approach was used that helps address policy co-occurrence. The most common approaches were adjusting for measures of co-occurring policies; defining the outcome on subpopulations likely to be affected by the policy of interest (but not other co-occurring policies); and selecting a less-correlated measure of policy exposure. As health research increasingly focuses on policy changes, we must systematically assess policy co-occurrence and apply analytic solutions to strengthen studies on the health effects of social policies.

State firearm laws, gun ownership, and K-12 school shootings: Implications for school safety

Limited research has been conducted on the state-level factors that may be associated with intentional school shootings. We obtained school shooting data from the Washington Post that identified any act of intentional interpersonal gunfire in a K-12 school over the course of two decades. We also compiled new data on active school shootings during the same twenty-year time period, which identified any attempted mass shooting incident in a K-12 school. We conducted a time-series analysis to measure the association of permissiveness of state firearm laws and state gun ownership with K-12 school shootings and active shootings. More permissive firearm laws and higher rates of gun ownership were associated with higher rates of both school shootings and active school shootings after controlling for critical covariates. Specific recommendations for K-12 schools to consider as they seek to prevent acts of intentional gunfire on school grounds are presented.

Impact of Firearm Surveillance on Gun Control Policy: Regression Discontinuity Analysis

BACKGROUND

Public mass shootings are a significant public health problem that require ongoing systematic surveillance to test and inform policies that combat gun injuries. Although there is widespread agreement that something needs to be done to stop public mass shootings, opinions on exactly which policies that entails vary, such as the prohibition of assault weapons and large-capacity magazines.

OBJECTIVE

The aim of this study was to determine if the Federal Assault Weapons Ban (FAWB) (1994-2004) reduced the number of public mass shootings while it was in place.

METHODS

We extracted public mass shooting surveillance data from the Violence Project that matched our inclusion criteria of 4 or more fatalities in a public space during a single event. We performed regression discontinuity analysis, taking advantage of the imposition of the FAWB, which included a prohibition on large-capacity magazines in addition to assault weapons. We estimated a regression model of the 5-year moving average number of public mass shootings per year for the period of 1966 to 2019 controlling for population growth and homicides in general, introduced regression discontinuities in the intercept and a time trend for years coincident with the federal legislation (ie, 1994-2004), and also allowed for a differential effect of the homicide rate during this period. We introduced a second set of trend and intercept discontinuities for post-FAWB years to capture the effects of termination of the policy. We used the regression results to predict what would have happened from 1995 to 2019 had there been no FAWB and also to project what would have happened from 2005 onward had it remained in place.

RESULTS

The FAWB resulted in a significant decrease in public mass shootings, number of gun deaths, and number of gun injuries. We estimate that the FAWB prevented 11 public mass shootings during the decade the ban was in place. A continuation of the FAWB would have prevented 30 public mass shootings that killed 339 people and injured an additional 1139 people.

CONCLUSIONS

This study demonstrates the utility of public health surveillance on gun violence. Surveillance informs policy on whether a ban on assault weapons and large-capacity magazines reduces public mass shootings. As society searches for effective policies to prevent the next mass shooting, we must consider the overwhelming evidence that bans on assault weapons and/or large-capacity magazines work.