Laws that limit potential shooters’ access to firearms by requiring permits may reduce the incidence of mass shootings, and laws that limit the number of shots that can be fired before reloading may reduce the severity of mass public shootings when they do occur. This is the bottom line of a recently published article in Law and Human Behavior. Below is a summary of the research and findings as well as a translation of this research into practice.
Featured Article | Law and Human Behavior | 2020, Vol. 44, No. 5, 347-360
The Relation Between State Gun Laws and the Incidence and Severity of Mass Public Shootings in the United States, 1976 –2018
Michael Siegel, Boston University School of Public Health
Max Goder-Reiser, Boston University School of Public Health
Grant Duwe, Minnesota Department of Corrections
Michael Rocque, Bates College
James Alan Fox, Northeastern University
Emma E. Fridel, Florida State University
Objective: In this study, we analyzed the relationship between state firearm laws and the incidence and severity (i.e., number of victims) of mass public shootings in the United States during the period 1976 –2018. Hypotheses: We hypothesized that states requiring permits to purchase firearms would have a lower incidence of mass public shootings than states not requiring permits. We also hypothesized that states banning large-capacity ammunition magazines would experience a lower number of victims in mass public shootings that did occur than states without bans. Method: We developed a panel of annual, state-specific data on firearm laws and mass public shooting events and victim counts. We used a generalized estimating equations logistic regression to examine the relationship between eight state firearm laws and the likelihood of a mass public shooting. We then used a zero-inflated negative binomial model to assess the relationship between these laws and the number of fatalities and nonfatal injuries in these incidents. Results: State laws requiring a permit to purchase a firearm were associated with 60% lower odds of a mass public shooting occurring (95% confidence interval [CI: -32%, -76%]). Large-capacity magazine bans were associated with 38% fewer fatalities (95% CI [-12%,-57%]) and 77% fewer nonfatal injuries (95% CI [-43%, -91%]) when a mass shooting occurred. Conclusion: Laws requiring permits to purchase a gun are associated with a lower incidence of mass public shootings, and bans on large capacity magazines are associated with fewer fatalities and nonfatal injuries when such events do occur.
firearms, mass public shootings, homicide, state laws, policy
Summary of the Research
“The recent occurrence of high-profile mass shootings, such as the tragedies in Parkland (Florida), Las Vegas (Nevada), El Paso (Texas), and Dayton (Ohio), has led to growing frustration and vigorous debate regarding policies intended to prevent these events. Although mass public shootings are a rare form of violence, there is general agreement— based on combined data from both the supplementary homicide reports and searches of online newspaper databases— that both the incidence and the severity of these events have increased in recent years. Given this increase in morbidity and mortality, and the fear these incidents instill, it has never been more important to identify laws that will help curtail the incidence and/or severity of mass public shootings in the United States. However, there is scant research into the effectiveness of gun laws in preventing mass public shootings or reducing the number of victims in such incidents” (p. 348).
“In this study, we took advantage of two new databases to further the existing research on the association between state firearm laws and mass public shootings by addressing limitations in both the predictor and outcome variables. First, we used a novel database that coded the status of 89 different state gun laws from 1976 to the present, using clearly defined criteria for identifying each law. Second, we used a comprehensive database of mass public shooting incidents from 1976 through 2018 assembled by combining all existing mass shooting databases and extensively evaluating each identified case. This triangulated data collection strategy incorporated information from the SHR, from existing databases that utilized news media reports, and from original searches of the entire database of news stories at multiple media resource websites” (p. 350).
“To our knowledge, this is the first paper to examine state firearm laws and their separate relationship with the likelihood of a mass public shooting and with the number of fatalities when such an event occurs. We found a robust relationship between state laws that require permits for the purchase and/or possession of guns and the incidence of mass public shootings and between large-capacity magazine bans and the number of deaths resulting from a mass public shooting if one does occur. However, we did not find any significant association between assault weapons bans or other firearm laws and either of these outcomes. Additionally, we found that large-capacity magazine bans are also associated with a lower number of nonfatal injuries when a mass public shooting occurs” (p. 354).
“Our finding that laws requiring permits to purchase or possess firearms are associated with a lower incidence of mass public shootings … supports the theoretical framework that we adapted from Cook (1983), which posits that limiting the availability of firearms may reduce the incidence of mass public shootings by increasing the costs of obtaining a gun in both the legal and illegal markets and that this increased cost could be enough to deter a potential mass shooter. State gun permit requirements have been shown to decrease firearm homicide rates and to reduce straw purchasing or trafficking of guns that diverts them into the illegal market” (p. 354).
“[W]e did not find that universal background check laws are related to the likelihood of mass public shootings. Background checks are typically conducted through the FBI National Instant Criminal Background Check System, which consults only national databases. State mental health, drug use, and criminal databases are not searched, and several studies have documented severe limitations of state reporting to the National Instant Criminal Background Check System database. In contrast to the federal background check system, states that require their own gun permits typically have detailed procedures that involve a check of multiple state databases and often require fingerprints rather than relying solely on self-reported information. Also, states that conduct their own background checks or delegate this responsibility to local authorities have lower firearm homicide rates than states that rely solely on federal background checks. Requiring permits to purchase or possess firearms is an effective mechanism for conducting effective criminal background checks at the local level” (p. 354).
“[We found that] state laws prohibiting large-capacity ammunition magazines are associated with fewer fatalities and nonfatal injuries in mass public shootings… It is plausible that a ban on large-capacity magazines would not stop mass shootings per se but could at least reduce the number of fatalities and nonfatal injuries in such events because the shooter can fire fewer rounds before having to reload. This is consistent with a body of literature demonstrating that fatality counts in mass shootings are higher when a large-capacity magazine is used by an assailant” (p. 354-355).
“In contrast to high-capacity magazine bans, we did not find support for the often-claimed association between assault weapon bans and mass public shootings… Our failure to identify an association of assault weapons bans and the incidence of, or fatalities in, mass public shootings could be explained by the fact that assault weapons are typically defined by cosmetic features rather than characteristics that directly affect the lethality of the firearm or by the relative infrequency of assault weapon use in mass public shootings. Most semiautomatic firearms are not assault weapons as defined by state laws but are functionally equivalent. They are manufactured without the accessories, such as bayonet lugs, flash suppressors, and grenade launchers, that characterize assault weapons. Moreover, the firing rate of all semiautomatic weapons is the same, regardless of whether they are military-style assault weapons or just handguns, namely the speed at which the shooter can squeeze the trigger. What makes assault weapons so lethal is not any particular functional feature but simply the fact that these firearms are designed to accommodate high-capacity magazines. This may explain our finding that large-capacity magazine bans, but not assault weapon bans, were related to the number of casualties in mass public shootings” (p. 355).
“[We found] that only two policies—permit requirements and large capacity magazine bans—were related to mass public shootings…[W]e failed to find a relation between may-issue laws or violent misdemeanor laws and mass public shootings. Because may-issue laws affect only the ability to carry a concealed gun not the ability to purchase a firearm, one might not expect these policies to affect mass public shootings. Violent misdemeanor laws are designed to prevent adjudicated violent criminals from possessing firearms; however, in a substantial proportion of mass shootings, there is no history of a criminal conviction for a violent crime or the crime involves domestic violence. Studies have documented serious loopholes in the confiscation of firearms from domestic violence offenders. Strengthening the procedures for the surrender of firearms by persons adjudicated for domestic violence or served with restraining orders may be necessary to observe a measurable effect of these policies on rare mass public shooting events. Similarly, our failure to find a relationship between relinquishment laws and mass public shootings could have more to do with the lack of enforcement of these laws than with a conceptual problem with the idea of limiting potential shootings by making sure that people who become prohibited from possessing a firearm are disarmed” (p. 355).
Translating Research into Practice
“Because of the cross-sectional nature of this study, we cannot definitively conclude that implementing a specific law would lead to a change in the incidence or severity of mass public shootings. Nevertheless, our research suggests three potential policy implications that must be balanced with citizens’ right to bear arms under the Second Amendment of the U.S. Constitution. First, to reduce the incidence of mass shootings, the primary objective should be to limit potential shooters’ access to firearms generally. One interpretation of our findings is that requiring permits to purchase or possess a firearm may limit potential shooters’ access to firearms. Furthermore, laws requiring permits to purchase or possess firearms may be more effective than universal background checks because they rely on state or local officials, who have the most direct access to criminal, mental health, and drug- and alcohol-related records. In contrast, universal background checks rely on FBI data, which are often incomplete” (p. 356-357).
“Second, to reduce the severity of mass public shootings when they do occur, the primary goal should be to limit the number of shots that can be fired before the shooter has to reload. This can be accomplished by restricting ammunition magazines to no more than 10 rounds. The 1994 Assault Weapons Ban is an example of a policy that sought to limit the severity of mass shootings. Included in that legislation was a ban on magazines that could hold more than 10 rounds. Recently several prominent voices have called for a renewal of the Assault Weapons Ban. Because our results did not show any association between assault weapons bans and mass public shootings, it may be more effective to focus on magazine capacity rather than trying to define assault weapons in general” (p. 357).
“Third, our failure to find a relationship between laws that prohibit people with a history of violence from possessing firearms and that require relinquishment of firearms by people who do become prohibited from possessing them may indicate weaknesses in the practical application of these laws. Few states have statutory-based procedures for confiscating firearms from people who are adjudicated for violent misdemeanors—such as domestic violence offenses— or who are served with protection orders. Future studies should examine not only the enactment of laws but also their enforcement” (p. 357).
This study provides evidence that state laws requiring permits to purchase a gun are related to a lower incidence of mass public shootings and that state bans on large capacity magazines are related to fewer fatal and nonfatal injuries when such events do occur. Policymakers wanting to address specifically the morbidity and mortality from mass shootings would be prudent to adopt permit-to-purchase laws and large-capacity ammunition magazine bans to reduce both the incidence of mass public shootings and the number of casualties if such events do occur. They should take these findings into account in combination with the substantial body of research on the effect of state firearm laws on other types of firearm violence and with consideration of citizens’ right to bear arms under the Second Amendment of the U.S. Constitution” (p. 357).
Other Interesting Tidbits for Researchers and Clinicians
“Perhaps the most surprising negative finding was that extreme-risk protection orders were not related to the incidence of mass public shootings. However, our definition of extreme-protection order laws included those in which law enforcement personnel are authorized to initiate a proceeding, regardless of whether family members can do so. We could not examine extreme-risk protection order laws that allow family members to intervene because only two states had such laws in place for more than 1 year during the study period. It may be that family members are in the best position to recognize people with access to guns who are at great risk of harming others or themselves. If this were the case, it could explain our failure to find any significant association between mass public shootings and laws that rely on law enforcement officials to identify at-risk individuals” (p. 355-356).
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