rget education toward treatment and service providers and members of
the criminal justice community to help reduce the notion that victims with SUDs are manipulative and to help with understanding the full impacts of trauma.3
Issue:  Certain busines


eds resulted in numerical separations between tiers that were less clear than the separations that resulted when we used the clustering algorithm in the initial tiering. This can occur because, for example, when the final expected value score for a n


re less likely to be identiﬁed.
Sex trafﬁcking victims with SUDs are often frequent
users of emergency services and are seen as hostile and uncooperative by ﬁrst responders because of their addiction and trauma.Develop and implement training for law


nd support, assist victims when needed, and help victims navigate processes.1
Trafﬁcking victims might not report the trafﬁcking or
other victimizations they have experienced to law enforcement because they do not trust criminal justice actors—parti


ation-sharing barriers (following the models of gang, fraud, and drug task forces).
Particularly when SUDs are involved, sex trafﬁcking
victims might be unwilling or unable to engage in traditional court or problem-solving courts.Develop policies to


ailability of programs and shelters for these victims.2
Juvenile and adult victims present different challenges
and require different services to treat SUDs and trauma (e.g., issues related to needing a guardian present to talk with the minor, lengt


les around participation that are difﬁcult for victims with SUDs and complex trauma to meet.Increase the availability of low-barrier, wraparound programs
that are speciﬁc to trafﬁcking victims and offer victims both choice and voice in the treatment


tatus and
sentencing considerations when someone is initially identiﬁed as an offender.
Trafﬁcking victims often lack the stability for long-term
participation in criminal justice cases, and trafﬁckers use SUDs to manipulate victims and keep them f


ent service delivery approaches for justice- and community-based entities, in terms of the ability to address the nexus between trafﬁcking and SUDs with survivor-centered, quality, timely, connected, safe, and accessible services.
There is often a di


ions on what defense attorneys are able to do in terms of undermining or attacking victims’ credibility. This could also increase victims’ likelihood of participation in the long term.Table A.2—Continued23NOTES
1   The Substance Abuse and Mental Heal


 Journal of Public Health , Vol. 109, No. 2, February 2019,
pp. 289–295.
Goodison, Sean E., Michael J. D. Vermeer, Jeremy D. Barnum,
Dulani Woods, and Brian A. Jackson, Law Enforcement Eﬀorts to
Fight the Opioid Crisis: Convening Police Leaders,


8–663.
Lambert, Laura, “Stockholm Syndrome,” Encyclopedia Britannica,
undated. As of October 26, 2021: https://www.britannica.com/science/Stockholm-syndrome
Love, Hanna, Jeanette Hussemann, Lilly Yu, Evelyn McCoy,
and Colleen Owens, Justice in Thei


reports/RRA108-3.html25Acknowledgments
The authors would like to acknowledge the participation and assistance of the members, listed in the report, of the workshop on  sex trafﬁcking
and substance use. This effort would not have been possible withou


in public policy.
Dulani Woods  is a quantitative analyst adept at data acquisition, transformation, visualization, and analysis. His research typically focus es
on justice and homeland security policy. He began his career as a Coast Guard ofﬁcer o


t be of interest are
• Sean E. Goodison, Michael J. D. Vermeer, Jeremy D. Barnum, Dulani Woods, and Brian A. Jackson, Law Enforcement
Efforts to Fight the Opioid Crisis: Convening Police Leaders, Multidisciplinary Partners, and Researchers to Identi


THIRD EDITION
The
Science
of Gun
Policy
A Critical Synthesis of Research Evidence
on the Effects of Gun Policies in the United States
Rosanna Smart, Andrew R. Morral, Rajeev Ramchand,  Amanda Charbonneau,
Jhacova Williams, Sierra Smucker, Samantha


tion of our research findings and recommendations,
disclosure of the source of funding of published research, and policies to ensure intellectual independence.
For more information, visit www.rand.org/about/research-integrity.
RAND’s publications d


rinciples that sometimes drive policy disagreements. Rather, our focus is strictly
on the empirical effects of policies on the eight outcomes specified in this report. All of our
resources are publicly available on the project website at www.rand.o


tin Lee, Emily Hoch, and Kyleanne Hunter.
Also within RAND, we wish to acknowledge the exceptional support we received from
our research librarians, Roberta Shanman and Sachi Yagyu; our publication editor, Blair
Smith; and members of RAND’s Office


ng and permitting requirements
8. waiting periods
9. firearm safety training requirements
10. lost or stolen firearm reporting requirements
11. firearm sales reporting, recording, and registration requirements
12. bans on the sale of assault weap


 (a
requirement for a causal effect) and that studies include a control group or comparison group
(to demonstrate that the purported causal effect was not found among those who were not
exposed to the policy).
For studies that met our inclusion cr


concerning the effects the laws are likely to produce.
Table S.1 summarizes our evidence ratings for all policy and outcome pairings. Several
outcomes show multiple ratings, and these correspond to different characterizations of the
specific polic


Prohibited PossessorsExtreme Risk Protection
OrdersBack-
ground
Checks Licensing and Permitting
RequirementsWaiting PeriodsFirearm Safety Training
RequirementsLost or Stolen Firearm
Reporting RequirementsFirearm Sales Reporting,
Recording, an


rt term L
NOTE: I = inconclusive; L = limited; M = moderate; S = supportive. When we identified no studies meeting eligibility criteria, cells are blank.  = the policy increases the outcome; ê = the
policy decreases the outcome. K–12 = kindergarte


 gun use means that we do not have a way of directly estimating how the benefits of
these laws (in terms of the number of child lives saved) compares with the possible costs (in
terms of forgone opportunities for self-defense).
In the section that


 laws establishing firearm prohibitions
for individuals subject to domestic violence restraining orders decrease total and firearm-
related intimate partner homicides, and there is limited evidence that laws prescribing a
mechanism for ensuring the


on laws, waiting-period laws, permit-to-purchase
laws, and child-access prevention laws.
Conclusion 8.  There is limited evidence that laws prohibiting the purchase or possession
of guns by individuals with histories of adjudicated mental illness o


going program of research fund -
ing. This could include investments in firearm research portfolios not only at the Cen -
ters for Disease Control and Prevention and the National Institutes of Health but also
at the National Institute of Justice and


asonable compromise
between cost and the public’s need for more-detailed information. Release of the data
from this expansion of the National Crime Victimization Survey should be a priority,
however, because the expansion began six years ago. In a


lly and legally feasible, at least in
some places. This decision meant that none of the policies we examined would dramatically
increase or decrease the stock of guns or gun ownership rates in ways that might produce
more readily detectable effect


Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun PoliciesxviiiRAND Corporation, The Science of Gun Policy: A Critical Synthesis of Research Evidence on
the Effects of Gun Policies in the United States , San


e Sale of Assault Weapons and High-Capacity Magazines  ........................ 227
State Implementation of Bans on the Sale of Assault Weapons and High-Capacity
Magazines  ............................................................................


tios Associated with the Effect of Concealed-Carry Laws
on Mass Shootings  ........................................................................ 353
 18.6. Incidence Rate Ratios Associated with the Effect of Concealed-Carry Laws
on the Gun Ind


o-thirds of these deaths are suicides (Kochanek et al.,
2019). Another 50,000 to 150,000 Americans per year receive care in a hospital for a nonfatal
gun injury (Schnippel et al., 2021; Kaufman et al., 2021; Avraham, Frangos, and DiMaggio,
2018).2


orporation,
2018), which synthesized the available scientific data on the effects of 13 classes of firearm
policies on firearm deaths, violent crime, the gun industry, participation in hunting and sport
shooting, and other outcomes. It built and e


igat -
ing the effects of a law are unavailable. Typically, therefore, we cannot conclude that a lack of
evidence is evidence that a policy has no effect or even a small effect. We can conclude only
that we do not yet know what the policy’s effects


 Research Evidence on the Effects of U.S. Gun Policies6that have been used to shape how guns are used in the United States, and research is avail -
able on the effectiveness of other approaches, such as public information campaigns, safety
and train


and suicide attempts. From a societal perspective, the most important of these out -
comes is total suicide; that is, the goal is to reduce the total number of suicide deaths regard -
less of the method used in the suicide attempt. In many cases, how


justed rate standardizes the crude (observed) suicide rate to allow comparisons across time
that are not confounded by changes in the age distribution of the population. Nevertheless, the crude rate
and the absolute number of suicides have both inc


onneg -
ligent manslaughter, 36.4 percent of robberies, and 27.6 percent of aggravated assaults in 2019
(FBI, 2022b). Although the Uniform Crime Reporting Summary Reporting System has been
a key source of crime data for decades, 2020 marked its fin


h examining nonfatal unintentional injuries. There
were close to 21 million unintentional injury discharges from emergency rooms in 2020, of
which 29,317 (less than 1 percent) were caused by a firearm (CDC, 2022c).4 These reports
omit injuries tha


s more broadly.
Police Shootings
Police shootings of civilians have triggered fierce debates locally and nationally about when
use of lethal force is appropriate and whether it is being used disproportionately against
minorities. Although the FBI h


 typically has been measured in the empirical literature using self-reports
on surveys of gun owners, although some studies have used firearm deaths coded as justifi -
able homicides to investigate subsets of defensive gun use. Although there are so


es, 2022). The literature on defensive
gun use and the challenges of defining and measuring such use were reviewed in the first edi -
tion of this report (see RAND Corporation, 2018, Chapter Twenty-Three).
Hunting and Recreation
Federal statistics


ut 1 percent were held by importers
(Bureau of Alcohol, Tobacco, Firearms and Explosives, 2021).
Organization of This Report
The report is organized into five parts. Part A introduces the project scope and objectives in
Chapter One and the methods


, Catherine, and David Hemenway, “Too Many or Too Few Unintentional Firearm
Deaths in Official US Mortality Data?” Accident Analysis and Prevention , Vol. 43, No. 3, 2011,
pp. 724–731.
Barber, C., D. Hemenway, J. Hochstadt, and D. Azrael, “Underest


 ,
Vol. 25, No. 3, 2006a, pp. 691–735.
Cramer, Clayton E., “Why the FBI’s Justifiable Homicide Statistics Are a Misleading Measure
of Defensive Gun Use,” University of Florida Journal of Law and Public Policy , Vol. 27, 2016,
pp. 505–514.
Doucette


Epidemiology , Vol. 2, No. 26, 2015a.
Hodur, Nancy M., F. Larry Leistritz, and Kara L. Wolfe, “Developing the Nature-Based Tourism
Sector in Southwestern North Dakota,” Great Plains Research: A Journal of Natural and Social
Sciences , Vol. 18, S


 Fears of Gun
Control Subside , Los Angeles, Calif., IBISWorld Industry Report 33299a: Guns and Ammunition
Manufacturing in the U.S., June 2017.
Luo, Michael, and Mike McIntire, “Children and Guns: The Hidden Toll,” New York Times ,
September 28,


h Coding with an Intent-Based Classification Approach,” Pediatrics , Vol. 111,
No. 4, 2003, pp. 741–744.The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies18Schildkraut, Jaclyn, H. Jaymi Elsass, a


cies
The third edition of this report updates our review of evidence for the effects of the 18 policies
included in the second edition. Our approach to selecting these policies, which is described
in greater detail in Smart et al. (2020), was guide


restricting our
evaluation to state policies, we exclude local interventions (e.g., problem-oriented policing,
focused deterrence strategies) that have been evaluated in prior meta-analyses (Braga, Papa -
christos, and Hureau, 2014; Braga and Weisb


• gun OR guns OR firearm* OR handgun* OR shotgun* OR rifle* OR longgun* OR
machinegun* OR “machine gun*” OR pistol* OR “automatic weapon” OR “assault
weapon” OR “semi-automatic weapon*” OR “automatic weapons” OR “assault weapons”
OR “semiautomatic


WorldCat Catalog of books, web resources, and other material worldwide.
Scopus An abstract and citation database with links to full-text content, covering
peer-reviewed research and web sources in scientific, technical, medical, and social
science


ectional analysis or leveraged the time-series
nature of the analyzed data). Thus, we established hierarchical selection criteria that were less
restrictive at the stage of title and abstract review. We developed all criteria using our research
qu


onal Firearms Agreement in Australia, see RAND Corporation, 2018,
Chapter Twenty-Four).
Full-Text Review
Next, we used full-text review to ensure that the studies included thus far did not meet any of
the first set of exclusion criteria and to excl


vide all three types of evidence. Such a design can demon -
strate that the policy preceded the change in the outcome of interest, and it can rule out a
wider range of potential confounds, including historical time trends and the time-invariant
cha


trength of state child-access prevention laws
using a scale. This scale does not, however, combine the effects of multiple different law classes as we have
defined them, so we consider the study in our synthesis of evidence for the effect of child-


esearch syntheses.
For instance, in the main chapters of this report and the previous editions, we do not note
when papers provided no goodness-of-fit tests or other statistical evidence to justify their
covariate selections. We also do not focus


un policies
we studied. Indeed, in many cases, knowledgeable analysts disagree on even the direction of
the effects expected from the policies (Smart, Morral, and Schell, 2021). Thus, we discount
effects when the underlying study had methodologica


ses with low statistical power results in an uncom -
fortably high probability that effects found to be statistically significant at p < 0.05 are in the
wrong direction and all effects have exaggerated effect sizes (Gelman and Carlin, 2014). If
we


ale describing the strength of available evidence:
1. No studies. This designation was made when no studies meeting our inclusion criteria
evaluated the policy’s effect on the outcome.
2. Inconclusive evidence. This designation was made when studi


s, some studies published updates to earlier works that expanded the time
frame of the analysis, corrected errors, or applied more-advanced statistical methods to a
nearly identical data set. In these cases, we do not treat both the earlier and lat


n (2014)Table 2.3—ContinuedMethods35results; in addition, the estimated effects of policies in the two papers were identical for the
estimates of interest to us in this review. Table 2.4 lists the superseded studies and their super -
seding versions


.,
2015; Guettabi and Munasib, 2018; Kagawa et al., 2018; Kivisto and Phalen, 2018; Rudolph
et al., 2015), we inferred approximate standard errors from the p -value associated with a per -
mutation test presented to demonstrate the likely statistic


tings,” Journal of Law and Economics , Vol. 61, No. 3, August 2018, pp. 489–524.
Anderson, D. Mark, Joseph J. Sabia, and Erdal Tekin, Child Access Prevention Laws and Juvenile
Firearm-Related Homicides , Cambridge, Mass.: National Bureau of Economic


nomic Inquiry , Vol. 36, No. 2, 1998, pp. 258–265.
Benson, Bruce L., and Brent D. Mast, “Privately Produced General Deterrence,” Journal of Law
and Economics , Vol. 44, No. S2, 2001, pp. 725–746.
Black, Dan A., and Daniel S. Nagin, “Do Right-to-Carr


ffect of the Brady Act on Gun Violence,” in B. Harcourt,
ed., Guns, Crime, and Punishment in America , New York: New York University Press, 2003,
pp. 283–298.The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S


u Kalesan, Kristin A. Goss, and Michael Siegel,
“State Intimate Partner Violence–Related Firearm Laws and Intimate Partner Homicide Rates in
the United States, 1991 to 2015,” Annals of Internal Medicine , Vol. 167, No. 8, 2017, pp. 536–543.
Donohu


 the Frequency of Mass Shootings and Firearms Homicide,” Justice Quarterly ,
Vol. 38, No. 5, 2021, pp. 892–915.
Gelman, Andrew, and John Carlin, “Power Calculations: Assessing Type S (Sign) and Type M
(Magnitude) Errors,” Perspectives on Psychologi


 No. 2, May 1998, pp. 458–462.
Goodman-Bacon, Andrew, “Difference-in-Differences with Variation in Treatment Timing,”
Journal of Econometrics , Vol. 225, No. 2, December 2021, pp. 254–277.
Grambsch, P., “Regression to the Mean, Murder Rates, and Sha


ichard C. Fording, “The Effect of State Gun Laws on Youth Suicide
by Firearm: 1981–2017,” Suicide and Life‐Threatening Behavior , Vol. 51, No. 2, April 2021,
pp. 368–377.
Kaufman, Elinore J., Christopher N. Morrison, Erik J. Olson, David K. Humphre


,”
Homicide Studies , Vol. 9, No. 4, 2005, pp. 292–323.
La Valle, James M., “Rebuilding at Gunpoint: A City-Level Re-Estimation of the Brady Law and
RTC Laws in the Wake of Hurricane Katrina,” Criminal Justice Policy Review , Vol. 18, No. 4,
2007,


nces , Vol. 114, No. 46, 2017, pp. 12162–12165.
Ludwig, Jens, “Concealed-Gun-Carrying Laws and Violent Crime: Evidence from State Panel
Data,” International Review of Law and Economics , Vol. 18, No. 3, 1998, pp. 239–254.
Ludwig, J., and P. J. Cook


he Debate on Shall-Issue Laws, Continued,” Econ Journal Watch , Vol. 6, No. 2, 2009,
pp. 203–217.
———, “The Impact of Right-to-Carry Laws: A Critique of the 2014 Version of Aneja, Donohue,
and Zhang,” Econ Journal Watch , Vol. 15, No. 1, January 2


th Rates,” Injury Prevention , Vol. 11,
No. 2, 2005, pp. 77–83.
Roth, Jeffrey A., and Christopher S. Koper, Impact Evaluation of the Public Safety and
Recreational Firearms Use Protection Act of 1994: Final Report , Washington, D.C.: Urban
Institu


W. Cronin,
Ziming Xuan, and David Hemenway, “The Impact of State Firearm Laws on Homicide Rates in
Suburban and Rural Areas Compared to Large Cities in the United States, 1991–2016,” Journal of
Rural Health , Vol. 36, No. 2, 2020b, pp. 255–265.
Si


, E. R., and J. A. Mercy, “Disarming Batterers: The Impact of Domestic Violence Firearms
Laws,” in Jens Ludwig and Philip J. Cook, eds., Evaluating Gun Policy: Effects on Crime and
Violence , Washington, D.C.: Brookings Institution Press, 2003, pp.


ditions for the possession and purchase of firearms include certain criminal histories (e.g.,
conviction of a felony, conviction of a misdemeanor crime of domestic violence, or status as
a fugitive from justice), criteria related to mental illness


 young people—and therefore
reduce the gun violence and unintentional shootings they commit.
Firearm homicides and violent crimes disproportionately involve individuals under age
21, both as perpetrators and as victims. Indeed, in 2020, arrest rat


te -
mute, and Claire, 2008; Shah et al., 2000; Grossman, Reay, and Baker, 1999). Indeed, a 2019
study using high-quality data from the Violent Death Reporting System indicated that rifles
and shotguns were used in more than half of suicides among


 a significant issue. A 2015 survey suggests that up to 7 percent (4.6 million) of
U.S. children (defined as those aged 17 or younger) reside in homes where at least one firearm
is stored loaded and unlocked, a much higher estimate than reported in


inimum age laws on these outcomes are
driven by the relevant age group affected by the policy. For outcomes of violent crime and
non-self-inflicted injury, causal analyses could be improved with data that reported the age of The Science of Gun Poli


See Calif. Penal Code § 27505; Conn. Gen. Stat. § 29-34(b); Del. Code Ann. Tit. 24, §§ 901, 903; Fla.
Stat. § 790.065(13); Hawaii Rev. Stat. Ann. § 134-2(d); 430 Ill. Comp. Stat. 65/4(a); Ia. Code § 724.22(1),
(2); Md. Ann. Code Art. 27 §  5-134(b)


505; Fla. Stat. Ann. § 790.22;
Hawaii Rev. Stat. Ann. § 134-2; Ill. Comp. Stat. 65/3, 65/4; 13 Vt. Stat. Ann. § 4020(a). Although Hawaii’s law
is silent about sales, the state requires permits for all purchases, and permits are issued only to those


 (2004) examined the effect of state-level
changes in minimum purchase and possession age laws on suicide rates among those
aged 14–17 and 18–20. The authors used negative binomial regression models that employed
generalized estimating equations a


 Additional analyses among boys
and young men stratified by age group (0–19 and 20–24) suggested no statistically significant
effects, although both point estimates are negative and slightly stronger among males aged
20–24.
Using a similar empiri


laws, which guarantee the right to a concealed-carry permit for all citizens who are The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies62find suggestive effects consistent with minimum possession


ond approach used a difference-in-differences model to examine tempo -
ral trends in states that changed their minimum age requirements relative to states with no
policy change. The authors used a linear regression model that included state and year


e of less than 1.00 indicates that the law appears to reduce the
outcome. For example, if the effect size for the effect of background checks on suicides
were 0.92, we would expect the suicide rate to fall to 0.92 times the rate prior to passage of


 than federal law requires were associated with reductions in firearm suicides
among those 24 and younger. Finally, Raifman et al. (2020) reported that laws requiring a
minimum age of 21 for all handgun purchases were associated with significant re


 suicides among those aged 24
and younger.Evidence for this
relationship is
inconclusive.Higher minimum age
requirements for purchasing
a /f_irearm have
uncertain
effects on total
suicides.
Evidence for this
relationship is
moderate.Minimum age req


ession by
juveniles also established waiting periods and background checks, and other federal policy
passed in 1994 created major crime reduction programs (the Violent Crime Control and Law
Enforcement Act). If states that had not passed minimum a


he observed reduction in firearm homicides could be due to the
law or to other events occurring in Connecticut around the same time the law passed.
Siegel et al. (2019) estimated the effects of minimum age laws for handgun possession
on state homi


 with others in this figure. IRR values
marked with blue squares indicate that methodological concerns are discussed in the text. Green
circles indicate that we identified no significant methodological concerns. See Appendix B for details.
Evidence


g the effect of laws requiring either minimum
age to purchase or minimum age to possess a firearm. Gius (2015b) found a suggestive effect
consistent with minimum possession
age laws decreasing unintentional fire-
arm deaths among those aged 19 or


e minimum age requirements
examined in Luca, Malhotra, and Poliquin (2016).
Conclusions
We identified one qualifying study exam-
ining how minimum age requirements
for purchasing a firearm affect the inci-
dence of mass shootings. Luca, Malhotra,


Homicide Data Table 3: Murder Offenders, by
Age, Sex, Race, and Ethnicity, 2018,” webpage, Crime in the United States 2018, 2019a. As of
November 18, 2019:
https://ucr.fbi.gov/crime-in-the-u.s/2018/crime-in-the-u.s.-2018/tables/
expanded-homicid


lic Law 117-159, Bipartisan Safer Communities Act, June 25, 2022.
Puzzanchera, C., G. Chamberlin, and W. Kang, “Easy Access to the FBI’s Supplementary
Homicide Reports: 1980–2020,” Office of Juvenile Justice and Delinquency Prevention, 2021.
Raifma


renson, “Recreational Gun Use by California Adolescents,” Health
Education and Behavior , Vol. 32, No. 6, 2005, pp. 751–766.
Watkins, Adam M., Beth M. Huebner, and Scott H. Decker, “Patterns of Gun Acquisition,
Carrying, and Use Among Juvenile and


tting harm to others or to themselves.
Epidemiological evidence suggests that a diagnosis of mental illness alone has little rela -
tion to risk of interpersonal violence (Swanson et al., 2015); in particular, studies estimate
that between 2 percent


reviously expressed for 15 cases (11.3 percent), and informal concerns about the shooter’s
mental health had been previously expressed for 13 additional cases (9.8 percent). Although
mass public shooters are more likely to have a psychotic disorder


 opportunities
for defensive gun use. At the same time, such an expansion may decrease violent crime, mass
shootings, and suicides carried out by this population.
Indeed, evidence supports that expanding prohibitions associated with mental illness


pter Eight (on background checks). The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies82State Implementation of Prohibitions Associated with Mental
Illness
As of January 1, 2021, 35 states and the


Me. Rev. Stat. Ann. § 393; Mass.
Gen. Laws Ann. § 129B; Minn. Stat. Ann. § 624.713; N.J. Stat. Ann. § 2C:39-7; N.D. Cent. Code § 62.1-02-01;
Wash. Rev. Code § 941.040; Wisc. Stat. §§ 941.29, 51.20, 54.10.
6 Mo. Stat. Ann. § 571.070.
7 Mich. Comp. L


 significant behavioral, emotional,
or mental disorder” (Hawaii Rev. Stat. Ann. § 134-7). California has a long list of disqualifiers, including
threats of physical violence, various lengths of detention, and court-ordered evaluation and counseling


 rates among individuals in Flor -
ida with a disqualifying mental health condition relative to individuals diagnosed with a seri -
ous mental illness but not prohibited from purchasing a firearm. They found no significant
difference between suicide


nd FIGURE 4.1
Incidence Rate Ratios Associated with the Effect of Mental Health–Related
Prohibitions on Suicide
NOTE: IRR values marked with blue squares indicate that methodological concerns are discussed in the
text. See Appendix B for details.
E


f arrest both before and after the NICS reporting change, but the
magnitude of the decrease following NICS reporting was smaller than the reduction seen in
the “treated” group with a disqualifying condition. However, no statistical tests were pro -


ence that some
state or federal mental health–related pro-
hibitions on gun ownership reduce violent
crime . Evidence for the effect of these pro-
hibitions on total homicides and firearm
homicides specifically is inconclusive.
Outcomes Without St


ities, 2009–2015—Statistical Tables ,
Washington, D.C.: U.S. Department of Justice, Bureau of Justice Statistics, NCJ 250632, 2017.
Hughes, Karen, Mark A. Bellis, Lisa Jones, Sara Wood, Geoff Bates, Lindsay Eckley, Ellie
McCoy, Christopher Mikton,


es , Rockville, Md., 2022.
Swanson, Jeffrey W., “Mental Disorder, Substance Abuse, and Community Violence: An
Epidemiological Approach,” in J. Monahan and H. Steadman, eds., Violence and Mental
Disorder , Chicago, Ill.: University of Chicago Press


 firearm while subject
to a nontemporary restraining order protecting an intimate partner or the child of an inti -
mate partner (Vigdor and Mercy, 2006). Subsequently, in 1996, the Lautenberg Amendment
(Pub. L. 104-208) to the Gun Control Act of 1


itted by a spouse is nearly equal to the proportion committed
by a boyfriend or girlfriend (Cooper and Smith, 2011; Sabri, Campbell, and Messing, 2021).
Although it is possible that some of these unmarried partners were cohabitants (and thus
would


e the defendant was alleged to have threatened to kill the plaintiff. Furthermore, when
firearms are ordered surrendered, there is often no clear procedure for enforcing such orders
(Frattaroli, Zeoli, and Webster, 2021). For more information about


Evidence on the Effects of U.S. Gun Policies94or more individuals, not including the offender, murdered with firearms in one incident)
from 1999 to 2013 found that 40 percent involved familicide; additionally, about 20 percent
of all mass public sh


ers
to have a material effect on gun sales or the gun industry.
To understand the potential effect size of these policies, it would be helpful to have infor -
mation on the size of the affected population and the extent to which the laws succeed in


 further than just prohibiting possession of firearms by individuals sub -
ject to DVROs. Twenty-three states require (or allow judges to require) individuals to sur -
6 Alaska, Arizona, Hawaii, Kansas, Louisiana, Maine, Massachusetts, Michigan, Minn


et our inclusion criteria and examined how prohibitions on
gun possession associated with a domestic violence conviction affected suicide. Using data
from 1995 to 2004, Andrés and Hempstead (2011) assessed the association of men’s suicide
rates wi


is -
demeanors, Sen and Panjamapirom (2012) examined the effect of whether a state, in its back -
ground check process, checks on restraining orders and misdemeanors. Controlling for year
and census subregion fixed effects, baseline state suicide ra


) focused
on workplace homicides. The state laws that were analyzed in our included literature for this
class of policies primarily cover firearm prohibitions associated with DVROs and domes-
tic violence misdemeanors, although two studies also ana


 mechanism for requiring that they surrender all firearms.
Using a linear model controlling for state and year fixed effects, state-specific linear trends,
and a host of state-level covariates, the author identified the effect of the federal law by


e negative relationship of DVRO policies with intimate partner homicide rates
was suggestive in the absence of firearm relinquishment provisions but was large and statis -
tically significant in the presence of relinquishment requirements, indicatin


nificantly reduced rates of total and firearm homicide rates. State back -
ground checks on misdemeanor offenses showed uncertain effects (see Figure 5.2). However,
14 Zeoli et al. (2018) also estimated the effects of the federal DVRO-related prohib


ntile was
associated with a 5.3-percent reduction in workplace homicides between 2011 and 2017. The
gamma regression model used to generate this estimate included year fixed effects and six
demographic and economic covariates. The model did not in


e text. Green circles indicate that we
identified no significant methodological concerns. See Appendix B for details. DV = domestic violence.
IPH = intimate partner homicide.Figure 5.2—Continued
Prohibitions Associated with Domestic Violence
105qui


s on /f_irearm-
related intimate
partner homicides.The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies
106stalking convictions influence firearm-
related intimate partner homicides , and
there is


n mass shootings that involved a domestic relationship and those that did not.16
Among the 14 types of policies included in the study were four related to domestic violence:
firearm prohibitions for subjects of DVROs that include ex parte orders, f


ates, 1995–2004,” Health Policy , Vol. 101, No. 1,
2011, pp. 95–103.
Campbell, J. C., D. Webster, J. Kozio-McLain, C. Block, D. Campbell, M. A. Curry, F. Gary,
N. Glass, J. McFarlane, C. Sachs, P. Sharps, Y. Ulrich, S. A. Wilt, J. Manganello, X. Xu


ap in State Domestic Violence Gun Laws,” Kentucky Law Journal , Vol. 91,
No. 4, 2003, pp. 935–955.
Hemenway, David, Deborah Azrael, Andrew Conner, and Matthew Miller, “Variation in Rates
of Fatal Police Shootings Across U.S. States: The Role of Fir


w , Vol. 75, No. 2, 1999, pp. 365–390.
Public Law 90-618, Gun Control Act of 1968, October 22, 1968.
Public Law 103-322, Violent Crime Control and Law Enforcement Act of 1994, 1994.
Public Law 104-208, Section 658, Gun Ban for Individuals Convicted o


ster, Shannon Frattaroli, Barbara E. Claire, and Garen J.
Wintemute, “Removing Guns from Batterers: Findings from a Pilot Survey of Domestic
Violence Restraining Order Recipients in California,” Violence Against Women , Vol. 19, No. 5,
2013, pp. 6


fenders
present an especially elevated risk of violence to their partners. For this reason, state firearm-
surrender laws often focus on domestic violence offenders at the time they are convicted of
such crimes.
Although firearm-surrender laws exi


l may also transfer possession to
a licensed dealer for storage. See also Calif. Fam. Code § 6389. The individual shall surrender fire -
arms for the period of the protective order.
• Conn. Gen. Stat. Ann. § 29036k. The individual has two business d


ix
studies focus on surrender laws related to domestic violence. Vigdor and Mercy (2006) exam -
ined how intimate partner homicide is affected by laws that allow law enforcement officers
to confiscate firearms at the scene of alleged domestic viole


724.26; La.
Code Crim. P. Title XXXV, Art. 1001(A)(1), (2); 2018 Md. Chap. 251; Mass. Gen. Laws Ch. 140, §§ 129B,
129D; Minn. Stat. Ann. § 2242; Nev. Rev. Stat. Ann. §  202.361; N.J. Stat. Ann. §§ 2C:25-27; N.Y. Crim.
Proc. Law § 370.25; 2019 Ore.


ng the firearm ownership of newly
prohibited possessors and requiring that they surrender all firearms. That mechanism,
requiring the defendant to attest to having disposed of all their firearms, is a relatively weak
version of a surrender law. Ra


und only uncertain effects of these laws on
intimate partner homicides committed by any means, as well as uncertain effects for fire-
arm intimate partner homicides of women. Zeoli and Webster (2010), Díez et al. (2017), and
Zeoli et al. (2018) als


ntified homicides between 1984 and
2017 that involved four or more firearm
fatalities (excluding offender fatalities and
drug- or gang-related shootings) using the Federal Bureau of Investigation’s Supplementary
Homicide Reports and two additiona


 by prohibited possessors affect
mass shootings .Evidence for this
relationship is
inconclusive.Firearm-surrender laws
have
uncertain
effects on mass
shootings.FIGURE 6.2
Incidence Rate Ratios Associated with the Effect of Firearm-Surrender Laws on


Vol. 27,
No. 2, 2021, pp. 145–149.
Raissian, Kerri M., “Hold Your Fire: Did the 1996 Federal Gun Control Act Expansion Reduce
Domestic Homicides?” Journal of Policy Analysis and Management , Vol. 35, No. 1, Winter 2016,
pp. 67–93.
Sorenson, Susan


0 million to support state and local implementation of ERPOs; the U.S. Depart -
ment of Justice had previously published model ERPO legislation (U.S. Department of Jus -
tice, 2021). Currently, state lawmakers have adopted a wide range of legislation


he respondent possesses. If a respondent does not return firearms in his or her possession
once the order is served, the court may issue a warrant to authorize law enforcement officials
to retrieve the weapons.
ERPO laws are designed to respond to


he first year of Colorado’s 2020 ERPO law (Barnard et al., 2021).
Between 2006 and 2013, 58 ERPOs were served per year in Indiana; between 1999 and 2013,
51 orders were served per year in Connecticut (Kapoor et al., 2018). In contrast, in the first


of the high-risk individual’s behav -
ior, we could expect that a higher percentage of at-risk individuals would have their firearms
removed for their safety or to prevent violent crimes. In addition, laws that allow for ex parte The Science of Gun


rtion
of firearm suicides to total suicides, the authors estimated that an additional 72 suicide deaths
would have occurred in the absence of the gun removal. Researchers found similar results
in a study of persons subjected to gun seizure in Mari


Colo. Rev. Stat. § 13-14.5-104; Del. Code Ann. Tit.
10, § 7701, 7704 (family and household members can petition for non-emergency orders); Hawaii Rev. Stat.
Ann. § 134-C; 430 Ill. Comp. Stat. 67/35, 67/40; Md. Code Ann., Pub. Safety § 5-601(E)(2);


inia Tech
mass shooting in 2007.
Based on the 1999 enactment date of Connecticut’s ERPO law, the analyses showed
small and uncertain effects on firearm suicide rates and on nonfirearm suicide rates (see
Figure  7.1).13 Defining the postinterventio


o isolate the cause of any observed change to the pas-
sage of the law versus to other co-occurring factors, and the study may have had limited
power to detect meaningful effects.
Figure 7.1 displays the incidence rate ratios (IRRs) and CIs associat


 of ERPOs on murder rates generated mixed findings.
Specifically, Gius (2020b) found a possible reduction in total and firearm murder rates in
Connecticut but a possible increase in firearm murder rates in Indiana. Given the contradic-
tory evidenc


B. Shev, Christopher E. Knoepke, and Garen J. Wintemute, “Gun Violence Restraining
Orders in California, 2016–2018: Case Details and Respondent Mortality,” Injury Prevention ,
2022.
Roskam, Kelly, and Vicka Chaplin, “The Gun Violence Restraining Or


l W. Webster, “Use of Extreme Risk Protection Orders to Reduce Gun
Violence in Oregon,” Criminology and Public Policy , Vol. 20, No. 2, May 2021, pp. 243–261.135PART C
Evidence for the Effects of Policies
Regulating Firearm Sales and Transfers
Part


r transfers of firearms (such as gifts). Several states
have expanded this federal requirement to mandate that background checks be conducted for
all firearm sales and transfers, including those between private parties. Such laws are referred
to a


ent firearm without
undergoing a background check (Hepburn, Azrael, and Miller, 2022). For firearms purchased
through private sources, 66 percent were acquired without a background check; this percent -
age was higher in states without comprehensiv


tion, 2018, Chapter Nineteen), it is unclear the extent to Background Checks139which related disqualifying indicators assessed in the background check process (e.g., prior
felony convictions, adjudicated mental health problems) adequately proxy for


cs of crimi -
nal offenders or suicide victims beyond age, gender, and race/ethnicity. (The National Violent
Death Reporting System is an important exception, when that information is known.) In
some cases (e.g., restraining orders), an individual


1977 to 2014, Luca,
Malhotra, and Poliquin (2017) evaluated the effects of background check and waiting-period
laws on suicide rates among adults aged 21 or older. Their analysis was based on log-linear
models adjusting for national trends, state


 (or total
suicides) appear on both sides of the model equation, which can lead to biased law effect esti -
mates (National Research Council, 2004). Results from these models revealed only uncertain
effects of background check laws on overall and f


rovide strong evidence on the
effects of background checks.
McCourt et al. (2020) examined the effects of point-of-sale background check laws in
Pennsylvania (1995) and Maryland (1996) relative to synthetic control states , defined as those
witho


tes changed this policy during the study time frame that these
effects cannot persuasively be attributed to the background check policy as opposed to other
factors affecting suicides in the states around the same time their laws changed. Checks for


 concerns are discussed in the
text. Green circles indicate that we identified no significant methodological concerns. See Appendix B
for details.Figure 8.1—Continued
The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effec


d checks have
uncertain
effects on total
suicides.
Evidence for this
relationship is
inconclusive.Background checks have
uncertain
effects on /f_irearm
suicides.Background Checks147Effects on Violent Crime
Research Synthesis Findings
Of studies that


effects of background checks specifically (separate from wait -
ing periods, which were also imposed by the Brady Act) by comparing five of 32 states that were required to
implement background checks but that did not experience a change in their wai


te Sales
Lott (2010) examined how state-required background checks for private sales affect violent
crime. Detailed results that include coefficients and test statistics were available for only one
specification and for the outcome of homicide (Lot


e background
check requirements, the authors’ models instead showed that the permitting requirements
significantly reduced firearm homicides by 11  percent, while having uncertain effects on
nonfirearm homicides (see Chapter Nine). Because the aut


ckground check or
permit-to-purchase policies over the entire study period, only between seven and 11 states
were available to inform the constructed counterfactual; this leads to worse pre-intervention
fit and increases the likelihood that any es


r after
the law’s implementation and thereafter, a portion of the law effect will be captured by the Background Checks151lagged outcome term.13 Using a similar specification but with one additional year of data,
Kaufman et al. (2020) found a signif


und check policies as
opposed to other factors affecting homicides in the states around the same time their laws
changed. Additionally, the authors did not appear to make any adjustments to account for
serial correlation and thus likely overstated


 merged administrative records
from public health and criminal justice agencies to evaluate how changes in state reporting
of gun-disqualifying mental health records to the NICS affected violent crime arrest rates for
individuals with a disqualify


ent data for us to calculate IRRs and CIs for the effect size of interest, so these are not
displayed in the figure. The Swanson et al. (2016) estimate in the figure is the change from
before and after the NICS reporting requirements for legally di


le, so the
effect sizes from this study are not directly comparable with others in this figure. IRR values marked
with blue squares indicate that methodological concerns are discussed in the text. Green circles
indicate that we identified no signi


on homicides or murders.
Lott (2010) and Zeoli et al. (2018) found
uncertain effects of such laws. Siegel et al.
(2020b) found uncertain effects for uni-
versal background checks in rural areas,
but a significant 12-percent reduction in
homicide


ewed in the next Evidence for this
relationship is
moderate.Universal background
check laws may
decrease
total homicides.The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies
158chapter on permitting


states that may be correlated with both the presence of background check laws and the Evidence for this
relationship is
limited.Universal background
check laws may
decrease
/f_irearm homicides.Background Checks159incidence of school shootings limits


or permitting were associated with significant 50- to 60-percent
reductions in mass shooting incidence and fatalities; in contrast, laws requiring point-of-sale
background checks had only uncertain effects on mass shootings. However, as with most


ee (FFL) drop -
out rates between 1994 and 1998, comparing dropout rates in states without a background
check system in place prior to the 1994 Brady Act with states that did have background check
requirements in place prior to the federal law (Kop


dustry.
Outcomes Without Studies Examining the Effects of
Background Checks
We did not identify any studies that met our inclusion criteria and examined the effects of
background check policies on the following outcomes:
• unintentional injuries an


022.
Everytown for Gun Safety Support Fund, “Mass Shootings in the United States: 2009–2020,”
webpage, June 4, 2021. As of August 18, 2022:
http://everytownresearch.org/reports/mass-shootings-analysis/
Gius, Mark, “The Effects of State and Federal


,” Health and Social Work , Vol. 44, No. 4, 2019,
pp. 232–240.
Kopel, D. B., “Background Checks for Firearms Sales and Loans: Law, History, and Policy,”
Harvard Journal on Legislation , Vol. 53, 2016, pp. 303–367.
Koper, Christopher S., “Federal Le


https://www.rand.org/pubs/research_reports/RRA243-1.html
Sen, B., and A. Panjamapirom, “State Background Checks for Gun Purchase and Firearm
Deaths: An Exploratory Study,”  Preventive Medicine , Vol. 55, No. 4, 2012, pp. 346–350.
Siegel, Michael,


Shootings in the United States,” Criminology and Public Policy , Vol. 19,
No. 1, 2020, pp. 171–212.
Webster, Daniel W., Jon S. Vernick, and Maria T. Bulzacchelli, “Effects of State-Level Firearm
Seller Accountability Policies on Firearm Trafficking


 risk of inflict -
ing harm on themselves or others.
As with comprehensive background check laws, by restricting access to firearms for indi -
viduals presumed to present greater risk of misusing those firearms, licensing and permit -
ting requiremen


or more firearms loaded and unlocked, compared with 26 percent of individuals who
were not trained doing so (Berrigan et al., 2019). These results suggest that existing trainings
may not reduce unsafe firearm storage. Similarly, a 1995 survey found


n homicide rates.2 Specifically, if permit-to-purchase laws restrict
trafficking operations from in-state retailers, one should observe a larger share of crime guns
originating from out-of-state sources after law passage, as well as a reduction in


s or months
only,13 while those issued in other states may last years.14 In New Jersey, firearm identification
cards are required for rifles and shotguns and remain valid indefinitely, unless the issuing or
other law enforcement agency identifies


ach purchase, though with some differences.17 For example, Hawaii requires a permit for
each handgun purchase but allows multiple long-gun purchases under a single permit.
Some of the aforementioned jurisdictions have also extended their licensing a


icy were positive and significant for men aged 15–24.
However, the study models had a ratio of estimated parameters to observations of about one
to seven, the authors did not appear to adjust standard errors to account for serial correla -
tion, an


ates showed a suggestive 33-percent decrease in firearm
suicides relative to the synthetic control for Connecticut’s permit-to-purchase law enact -
ment and a suggestive 24-percent increase in firearm suicides following Missouri’s repeal of
permit-


ant
increase in suicides and firearm suicides among those aged 18–20. Andrés and Hempstead
(2011) found mixed results, with permitting requirements resulting in significantly lower
rates of suicide among men aged 45 or older but significantly high


 homicide rate was
19Although La Valle (2013) includes license-to-own and permit-to-purchase regulations as covariates in
his models for total and firearm homicide rates, no states enacted or repealed such laws during the period
of study (based on


dolph et al. (2015) found a significant decrease in firearm homicides
(and no statistically significant effect on nonfirearm homicides) from the implementation of
a permit-to-purchase law in Connecticut that strengthened background check requiremen


ed policy units, the
clustering adjustment to the standard errors in this study likely resulted in underestimated
standard errors and unreliable CIs (Cameron, Gelbach, and Miller, 2008; Schell, Griffin, and
Morral, 2018).
Four state-level studies


tudies (Crifasi et al., 2018b; Siegel et al., 2020b) considered the effects of
permit-to-purchase laws in urban areas specifically. Crifasi et al. (2018b) used county-level
data to estimate the effects of permit-to-purchase laws on firearm and nonf


i’s permit-to-purchase law
was associated with a significant increase in firearm homicides. McCourt et al. (2020) found Licensing and Permitting Requirements179FIGURE 9.2
Incidence Rate Ratios Associated with the Effect of Licensing and Permitting


this law. There-
fore, although we believe that there is evi-
dence that permit-to-purchase laws were
associated with reductions in total and
firearm homicides in three states, we are
not yet confident that other states can
expect similar results


and rare) outcome likely violated model
assumptions and rendered the results unreliable. The authors’ estimated linear probability
model can yield predicted probabilities of active shooting incidence that extend far outside
the definitional 0 to 1


empirical studies of mass shootings, incidents and fatalities are quite sparsely represented in
the data used for these models (i.e., incidents occurred at a rate of less than 0.4 per state-year,
and fewer than two deaths occurred per state-year).


arameters to observations of approximately one to four, and the study provided no
additional evidence to demonstrate appropriateness of model fit. Therefore, in accordance
with our review methodology, we discount the evidence provided by this analy


h, John H., and Forrest D. Nelson, Linear Probability, Logit, and Probit Models , Beverly
Hills, Calif.: Sage Publications, 1984.
Andrés, Antonio Rodríguez, and Katherine Hempstead, “Gun Control and Suicide: The Impact
of State Firearm Regulations


K., Keshia M. Pollack, and Daniel W. Webster, “Effects of State-Level Policy
Changes on Homicide and Nonfatal Shootings of Law Enforcement Officers,” Injury Prevention ,
Vol. 22, No. 4, 2016, pp. 274–278. The Science of Gun Policy: A Critical Synth


ensing, Point-of-Sale
Background Check Laws, and Firearm Homicide and Suicide in 4 US States, 1985–2017,”
American Journal of Public Health , Vol. 110, No. 10, October 2020, pp. 1546–1552.
Rudolph, K. E., E. A. Stuart, J. S. Vernick, and D. W. Webs


ors of
Domestic Violence and Their Associations with Intimate Partner Homicide,” American Journal
of Epidemiology , Vol. 187, No. 11, 2018, pp. 2365–2371.189CHAPTER TEN
Waiting Periods
The Brady Handgun Violence Prevention Act (the Brady Act), whic


 found that,
although almost no firearm suicides were committed by this population during the state’s The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies19015-day waiting period, the most elevated


ferred from federally licensed firearm dealers to prohibited persons because of delays in NICS
background checks that exceeded three business days (Criminal Justice Information Services
Division, 2022). Often, these delays result from missing data


etion of the background check within the requisite three-day period (Buchanan et al.,
2018). However, the small sample of mass shooting cases explored in this analysis makes gener -
alizations about the association of waiting periods and mass shooti


2021, four states and the District of Columbia impose a waiting period to
purchase any firearm.3 Five other states impose waiting periods for certain classes of fire -
arms.4 The length of waiting periods varies by state. For example, California and


18 unaffected states (plus the District of Columbia), the
states implementing and those not implementing waiting periods saw uncertain reductions
in suicide and firearm suicide rates. A subgroup analysis found a significant 9-percent reduc -
tion i


ting-period law might have reduced suicide attempts by other lethal means. The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies194mates were similar in their more-parsimonious specifications. Using


th signif-
icant negative effects on firearm suicide
rates; effects on total suicide rates were
negative and suggestive (Edwards et al.,
2018) or significant (Luca, Malhotra, and
Poliquin, 2017), depending on the study.
Given that both studies (


al before and after trends in states that enact waiting-period policies. In these
preferred specifications, models generally showed that states that enacted waiting periods
typically had lower rates of law enforcement officer deaths both before and


ification but covering a longer time frame (1977 to 2014) found that waiting periods resulted Waiting Periods197in large and significant reductions in total and firearm homicide rates among adults aged 21
or older (Luca, Malhotra, and Poliquin, 201


wait-
ing period (Roberts, 2009): A waiting
period of two to seven days significantly
reduced firearm-related intimate part-
ner homicide, 24-hour waiting periods
produced suggestive declines in firearm-
involved intimate partner homicides, and
w


ng periods: the number of days that purchasers
must wait before accepting delivery of a handgun and the number of days before accepting
delivery of a long gun. The authors’ regression analysis covered 1989–2014 and included con -
trols for time-inv


ngs.
Waiting Periods201Effects on the Gun Industry
Research Synthesis Findings
Two studies met our inclusion criteria and assessed how waiting periods influence the gun
industry or gun ownership. Brauer, Montolio, and Trujillo-Baute (2017) estimated


t study also found uncer-
tain effects of waiting periods on a proxy
measure for firearm demand (NICS back-
ground check rates), consistent with find-
ings of another study that indicated that
waiting periods had an uncertain rela-
tionship with ov


ent of Justice,
Federal Bureau of Investigation, 2020.
———, National Instant Criminal Background Check System (NICS) Section: 2020–2021
Operations Report , Washington, D.C.: U.S. Department of Justice, Federal Bureau of
Investigation, 2022.
Cumm


ber, “Suicide Mortality in the United States: The Importance of
Attending to Method in Understanding Population-Level Disparities in the Burden of Suicide,”
Annual Review of Public Health , Vol. 33, 2012, pp. 393–408.
Miller, M., D. Hemenway, and D


ire
gun purchasers or those requesting concealed-carry permits to show proof of formal safety
training on how to safely store, use, and maintain weapons. Public support for requiring
concealed-carry applicants to pass a test demonstrating safe and


(see Chapter Seventeen, on child-access pre -
vention laws). And the motivations of the individuals who receive firearm training could affect
the overall impact of the training programs. For example, some states require individuals to
attend safety


e
significantly more likely to report safe storage behaviors, although this does not provide good
evidence that the trainings cause more safe storage. Overall, it is likely that the effect of a
gun safety training course on firearm practices will


 Jersey, Rhode Island, and the District
of Columbia. See Calif. Penal Code § 26165; Conn. Gen. Stat. § 29-28(b) (Connecticut does not distinguish
between open- and concealed-carry permits); Del. Code Ann. Tit. 11, § 1441(a); Hawaii Rev. Stat. Ann.


ls used by Lott (2010)
specified training requirements using three separate variables that cannot be combined to
generate an overall or average effect, we do not present these estimates in a figure.
Two other studies (Crifasi, Pollack, and Webster,


or concealed carry, this study could not isolate the effects of firearm safety
training requirements. Thus, we do not present these estimates in a figure.
Conclusions
The one study that provided evidence for the effect of safety training requirement


fe, Gary Vercruysse, Julie Wynne, and
Andrew Tang, “Repeal of the Concealed Weapons Law and Its Impact on Gun-Related Injuries
and Deaths,” Journal of Trauma and Acute Care Surgery , Vol. 76, No. 3, 2014, pp. 569–575.
Hemenway, David, Steven Raushe


e firearms stolen were not recovered (Lang -
ton, 2012). Annual estimates of guns stolen for the 2010 to 2014 period were similar, at just
more than 251,000, with about 75 percent of theft incidents reported to police (Cook, 2018).
Data from police


illegal firearm trafficking, causal inference could be strengthened by examining
crime gun trace data, as well as changes in homicide or violent crime rates. Specifically, if
these laws restrict trafficking operations from in-state sources, one sho


s); N.Y. Penal Law § 400.10 (within 24 hours); Ohio Rev. Code § 923.20 (report
“forthwith”); R.I. Gen. Laws § 11-47-48.1 (within 24 hours); Va. H.B. 9 § 18.2-287.5 (within 48 hours); D.C.
Code Ann. § 7-2502.08 (report “immediately”).
4 Md. Ann. Cod


on system , which we define as a recordkeeping
system controlled by a government agency that both stores the names of current owners of
each firearm of a specific class and requires that these records are updated after firearms are
transferred to


ehaviors and firearm violence. For example, some researchers have
been granted access to information from the California Department of Justice Dealer Record
of Sale database, which contains records of legal handgun transfers that have occurred sinc


tifying and arresting suspects in firearm-related crimes, including violent and
property crimes, and firearm trafficking crimes. In California and other states that use these
records to identify prohibited possessors with weapons, data on firearm-i


nd, Michigan, and New Jersey. See Md. Code Ann., Pub. Safety §§ 5-101, 5-120, 5-145, Md. Code
Regs. 29.03.01.09(D); Mich. Comp. Laws §§ 28.422(5), 28.422a(2), 750.232; N.J. Stat. Ann. §§ 2C:58-2b,
2C:58-3h. In addition, Pennsylvania and Washington


nd Wade, 2016), and
we discounted that study’s evidence for
methodological reasons. Considering this
one study, we find inconclusive evidence
for the effect of firearm sales reporting,
recording, and registration requirements
on mass shootings


ing, recording, and registration requirements and the following outcomes:
• suicide
• violent crime
• unintentional injuries and deaths
• police shootings
• defensive gun use
• hunting and recreation.The Science of Gun Policy: A Critical Synthesis of


 Medicine , Vol. 166, No. 10, 2017, pp. 698–706.
Studdert, David M., Yifan Zhang, Sonja A. Swanson, Lea Prince, Jonathan A. Rodden, Erin E.
Holsinger, Matthew J. Spittal, Garen J. Wintemute, and Matthew Miller, “Handgun Ownership
and Suicide in Cal


t weapons  include
a specific list of firearm models (e.g., TEC-DC9, Beretta Ar70 [SC-70], Colt AR-15), as well as semiauto -
matic firearms that have at least two of a designated list of features (27 C.F.R. 478.11). In contrast, fully
automatic we


sed disproportionately in mass public
shootings and killings of law enforcement officers compared with murders overall. However,
these incidents are relatively rare. Data on mass shootings or active shooter events suggest
that 10 to 30  percent of


 relative
demand for these items, the availability of nonbanned weapons that serve as close substitutes,
and the costs of modifying existing weapon types to meet the requirements of the ban, to
name a few. A nationwide ban could also impact the in


nly
specific features. The laws that list specific banned models are similar jurisdiction to jurisdic -
tion, although the lists are not generally identical.
California is an example of a state that has a list of banned weapons, including rifles, sh


earm features, not specified
models of firearms.11
In addition to definitional differences, the laws are distinct in other ways—notably, their
treatment of grandfathered weapons. For example, the District of Columbia does not allow
grandfathering


 bans with firearm and total suicides. Estimates for the
effects of state assault weapon bans were based on policy changes in only three states with at
least three years of post- and pre-policy data, likely resulting in inaccurate estimates of unce


nd Marvell, 2018b). Using a log-linear model with two-way fixed effects, the authors
used a hybrid policy specification to estimate the joint effect of law passage on the levels and
trends in firearm homicide rates, controlling for state-level soci


 two states with changes to their laws and at least three
years of data before and after implementation of the changes, so the effects of this index are
not well identified in this model. In addition, it seems unlikely that the six socioeconomic
v


ffects on Mass Shootings
Research Synthesis Findings
We identified six studies that met our inclusion criteria and estimated the effects of state or
federal assault weapon bans on multiple-victim shooting incidents or casualties. Two of these
(Klar


; mass shooting deaths are included
in both the numerator and the denominator. Furthermore, the use of firearm homicides as a comparison
group has obvious methodological problems, given that the assault weapon ban (as well as other 1994 legis -
lat


gazine restrictions from 1990 to 2017. They used logistic regression for mass
shooting incidents and negative binomial models for counts of deaths in models with state
fixed effects, a continuous term for year to account for temporal trends, and st


epresent implausible effect
sizes, for some of the gun policies that we are studying.22 This indicates a serious model mis -
specification (Cox and Snell, 1989; Aldrich and Nelson, 1984) and prevents us from interpret -
ing the estimated coefficient


ate assault weapon bans on the annual incidence of mass shootings. Blau,
Gorry, and Wade (2016) found that the bans significantly reduced the annual incidence of
mass shootings. Webster et al. (2020) found uncertain evidence of state assault weapon


 and 1995, but prices returned
to pre-ban levels for the remainder of the study period. In contrast, the price of comparison
rifles remained constant over the same time frame.
Koper (2004) also examined manufacturer production of banned and compar


tical Synthesis of Research Evidence on the Effects of U.S. Gun Policies242Outcomes Without Studies Examining the Effects of Bans on
the Sale of Assault Weapons and High-Capacity Magazines
We did not identify any research that met our inclusion crit


-homicide-data-table-15.xls
———, “Table 28: Law Enforcement Officers Feloniously Killed, Type of Weapon, 2010–2019,”
webpage, Law Enforcement Officers Killed and Assaulted, 2020d. As of August 31, 2022:
https://ucr.fbi.gov/leoka/2019/tables/table-2


ffrey A. Roth, “The Impact of the 1994 Federal Assault Weapon
Ban on Gun Violence Outcomes: An Assessment of Multiple Outcome Measures and Some
Lessons for Policy Evaluation,”  Journal of Quantitative Criminology , Vol. 17, No. 1, 2001,
pp. 33–74.


es,” in Rajeev
Ramchand and Jessica Saunders, eds., Contemporary Issues in Gun Policy: Essays from the
RAND Gun Policy in America Project, Santa Monica, Calif.: RAND Corporation, RR-A243-2,
2021, pp. 1–30. As of August 31, 2022:
https://www.rand.


ting low-quality guns generally focus on handguns because they
are so commonly preferred by criminals. Using a nationally representative survey of crime
victims, the Bureau of Justice Statistics found that, in 2011, handguns were used in 73 percent


rearms
overall, plausibly lowering criminal access to such products if cost constraints are binding
for these individuals. Indeed, several studies have documented the high proportion of low-
quality and inexpensive handguns used in crimes (Vernick,


lue, a study in Boston suggested that these
types of weapons face the most exorbitant mark-ups in the illicit market (Hureau and Braga,
2018), indicating that there is a fixed cost of criminal-market transactions for well-known
low-quality handgun


otings. Between 2000 and 2016, 31 percent of mass
shooting victims were shot by handguns (Sarani et al., 2019). Further research is needed to
assess whether low-quality handgun regulations would reduce access to firearms among pos -
sible mass shoo


produced without quality regula -
tions (Kurtzleben, 2015). In 2018, after several deaths were linked to misfiring Remington firearms, some
7.5 million owners of the relevant gun models filed a class-action suit alleging that the guns can fire with


00, 31905; Mass. Gen. Laws Ann. 140 § 123; 9 N.Y. CRR 482.6.
5 Hawaii Rev. Stat. Ann. § 134-15; 720 Ill. Comp. Stat. 5/24-3(A)(h); Mass. Gen. Laws Ann. 140 §  123;
Minn. Stat. Ann. § 624.712; 9 N.Y. CRR 482.5.
6 Calif. Ann. Penal Code § 32015; Md. C


 significant 6-percent decrease in overall suicide rates and a 13-percent reduction
in the firearm suicide rate. However, because these estimates were based on law changes in
just three states, standard errors for the estimates are likely underesti


erences model to examine
how the passage (in 1988) and implementation (in 1990) of Maryland’s ban on low-quality
handguns influenced firearm homicide rates. The authors controlled for firearm homicide
rates in Pennsylvania and Virginia to account


ing the model may have been overfit and its
associated effect estimates and significance levels may be inaccurate.
Covering a later period, from 1999 to 2012, Webster, Crifasi, and Vernick (2014) also pro -
duced estimates of the effects of low-qua


s. One additional study meeting our inclusion criteria was discounted
on methodological grounds (Webster, Vernick, and Hepburn, 2002). Two studies found an
uncertain effect (Rosengart et al., 2005; Siegel et al., 2019), and two studies found that t


urthermore,
with only 15 observations, the ratio of estimated parameters to observations was less than
one to five, which is below the threshold for contributing to our summary of available evi-
dence (as explained in Chapter Two).
Conclusions
One


 Gun Trafficking and Criminal Gun Use , Washington, D.C.:
National Institute of Justice, 2003.
Koper, Christopher S., “Crime Gun Risk Factors: Buyer, Seller, Firearm, and Transaction
Characteristics Associated with Gun Trafficking and Criminal Gun


a M. Hepburn, “Effects of Maryland’s Law Banning
‘Saturday Night Special’ Handguns on Homicides,” American Journal of Epidemiology , Vol. 155,
No. 5, 2002, pp. 406–412.
Webster, Daniel W., Jon S. Vernick, Emma E. McGinty, and Ted Alcorn, “Preventin


263CHAPTER SIXTEEN
Stand-Your-Ground Laws
Self-defense has long been available as a criminal defense for fatal and nonfatal confronta -
tions. Traditionally, this defense imposes a duty to retreat before using force if safe retreat
is available. Sta


stand-your-ground policies in both their treated groups (states with the statute) and their The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies264comparison groups (states with stand-your-ground


cClellan
and Tekin, 2017; Cheng and Hoekstra, 2013).
There is likely to be little effect of stand-your-ground laws on hunting or recreational gun
use. However, should these policies encourage more individuals to obtain or carry firearms,
we might


ma, Alaska, Arizona, Georgia, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Mississippi,
Missouri, Montana, Nevada, New Hampshire, North Carolina, Ohio, Oklahoma, Pennsylvania, South
Carolina, South Dakota, Tennessee, Texas, West Virginia,


 those of Florida and Utah,8
sometimes with distinct features. A few other laws strayed further from the Florida and Utah
statutes; for instance, Mississippi’s law uses the term felony  rather than the narrower forcible
felony .9 Other states do n


2”; or a crime against someone who is “in the process of unlaw -
fully and forcefully entering, or has unlawfully and forcefully entered, a dwelling, residence, business prop -
erty, or occupied vehicle, or federally licensed nuclear power facility,


d Connecticut, it applies in the home or workplace.17
Some states exclude specific situations from applying under the stand-your-ground doc -
trine. In Louisiana, it “shall not apply when the person committing the homicide is engaged,
at the time of


9terfactual trends after states passed stand-your-ground laws. Because their analysis of sui -
cide rates was intended as a falsification test, the authors examined the effect of stand-your-
ground laws on firearm suicide rates only among the three s


 in total suicide rates associated
with these laws. Therefore, available stud-
ies provide inconclusive evidence for the
effect of stand-your-ground laws on total
suicides and firearm suicides.
Effects on Violent Crime
Research Synthesis Findings


 arrive at these results used a large
number of estimated parameters relative to observations (a ratio of about one to eight), mean -
ing the model may have been overfit, and thus its estimates of the laws’ effects may not gen -
eralize to other imp


980–2011) to estimate the effects of stand-
your-ground laws on murders, robberies, rapes, and aggravated assaults. Using a log-linear
model with controls for state, time, and 11 time-varying state effects, the author found that
these laws were ass


 -
tive and uncertain for small urban areas. However, because not every urbanization designa -
tion exists in every state (e.g., South Dakota has no county that is designated as a central city),
these stratified models were identifying effects from


data sets (Levy et al., 2020). Using descriptive statistics without consideration of potential con -
founds or temporal effects, the authors compared homicide rates in the periods before (2000–2004) and
during the time that 22 states implemented a s


am -
ined the effects of these laws in urban counties (large central metro and fringe metro). They
estimated Poisson regression models to understand how several state gun policies related to
firearm and nonfirearm homicide rates. They controlled fo


ic effect sizes but no average effect of the law, we do not display their estimates
here. And although McClellan and Tekin (2017) noted the marginal effects of stand-your-
ground laws on total homicides and stated that those estimates were statistic


earm homicides or firearm mur-
ders (Gius, 2016; Munasib, Kostandini,
and Jordan, 2018; Webster, Crifasi, and
Vernick, 2014; Siegel et al., 2019; Siegel
et al., 2020b; Knopov et al., 2019; Schell
et al., 2020), and one found uncertain
effects on


ility model can yield predicted probabilities of active shoot-
ing incidence that extend far outside the definitional 0 to 1 range of a probability, depending
on the particular combination of policies present in a given state. Moreover, the estimate


de, ranging from an uncertain 28-percent rise to a
significant 57-percent rise, depending on the model specification. However, given the rela-
tively short time frame studied and the large set of controls, the ratio of estimated parameters
to obser


013). We do not plot results from McClellan and Tekin
(2017) because the study is excluded from consideration on methodological grounds. We do
not plot results from Levy et al. (2020) because the paper does not provide standard errors or
CIs descr


2014). The author found that stand-your-ground laws were associated with
significant increases in the number of NICS background checks and significant declines Evidence for this
relationship is
inconclusive.Stand-your-ground laws have
uncertain
effe


lysis,” Social Science Journal , Vol. 53, No. 3, 2016, pp. 329–338.
Guettabi, Mouhcine, and Abdul Munasib, “Stand Your Ground Laws, Homicides and Gun
Deaths,” Regional Studies , Vol. 52, No. 9, 2018, pp. 1250–1260.
Hemenway, David, Chloe Shawah, and


e/do-stand-your-ground-laws-worsen-racial-disparitiesThe Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies284Sabbath, Erika L., Summer Sherburne Hawkins, and Christopher F. Baum, “State-Level Changes


 2022; see also Berrigan et al., 2019). Child-access
prevention (CAP) laws allow prosecutors to bring charges against adults who intentionally
or carelessly allow children to have unsupervised access to firearms. CAP laws aim to reduce
unintention


as adult offenders, with more than 80 per -
cent citing a friend, family member, or the black market as the source of the weapon (Webster
et al., 2002; LaFree and Birbeck, 1998).
Conceptually, the effects of CAP laws may extend beyond those age gro


rmine suicide risk. Further Child-Access Prevention Laws287research is needed to better understand the relationship among mental health, suicide risk,
firearm ownership, and firearm behaviors.
Since 2003, only one individual-level study provided in


this possibly indicates
that associations found between CAP laws and safe storage could be attributable to other
correlated factors, such as individual-level characteristics (e.g., the number and types of fire -
arms owned by survey respondents) or


ional
deaths by firearm have been shown to suffer from a range of coding errors, especially for chil -
dren (Rockett, Kapusta, and Coben, 2014; Barber and Hemenway, 2011; Barber et al., 2002).
These errors do not necessarily undermine the validity


rim. Law
§ 4-104; N.J. Stat. Ann. 2C: 58-15; Tex. Penal Code Ann. § 46.13.
7 California, Hawaii, Massachusetts, and the District of Columbia. Calif. Penal Code § 25200 (the child
must carry the unloaded gun off the premises for liability to attach)


ose for negligent storage, such as that the firearm was in a locked container21 or had been
rendered inoperable.22 Other exceptions include that the individual carried the firearm or it
was close enough to be easily retrieved,23 the defendant had n


16,30
and in another four states, a minor is under age 14.31
In eight states and the District of Columbia, the act of negligent storage of a firearm is a
misdemeanor.32 In Massachusetts, negligent storage is a felony. In nine other states, negligen


34 California, Nevada, Utah, and the District of Columbia.
35 Colorado, Connecticut, Georgia, and Indiana.The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies292Tennessee makes it a felony for par


o effect. These
findings were sensitive to the authors’ choices about model specifications: An alternatively
specified and worse-fitting model yielded uncertain effects.36 The authors also found that
CAP laws were associated with reductions in rat


, 2021);
(2) for many CAP states, the synthetic control consists of only one or two states; (3) effect size
magnitudes are not provided; and (4) conventional methods of inference for synthetic control
approaches are not used.
Using data from 1980


prohibiting reckless provision of guns to
children. They examined CAP law effects on nonfatal self-inflicted gun injuries recorded in
the Nationwide Inpatient Sample (NIS). Self-inflicted gun injuries include suicide attempts
and unintentional inj


om 1991 to 2016. Specifically,
the authors distinguished among three types of negligent storage CAP laws: those imposing
penalties if (1) a child could access the firearm, (2) a child did access a firearm, and (3) a child
accessed and used a firea


tions also were sig -
nificantly associated with the number of state provisions concerning negligent storage and
safety locks and the number of laws imposing criminal liability based on the age of children. The Science of Gun Policy: A Critical Synt


sociated with reductions in
suicides among those aged 14–17 and those aged 18–20.
We conclude that available research
offers moderate evidence that child-access
prevention laws reduce total suicides
among young people and inconclusive evi-
dence


 strengths, and the
fact that effects are found across mul-
tiple data sets, we conclude that there is
supportive evidence that child-access pre-
vention laws reduce firearm self-injuries
among young people (including firearm Evidence for this
rel


ge from reckless endangerment CAP laws, negligent storage laws
significantly predicted reduced homicide numbers, while the effects of reckless endanger -
ment laws on homicides were uncertain. They also found only uncertain evidence for the
effects


of CAP laws on fire -
arm homicide rates among victims ages 14 and under from 1991 to 2016. Specifically, the
authors distinguished among three types of negligent storage CAP laws: those imposing pen -
alties if (1) a child could access the firearm,


ve been overfit.
Sabbath, Hawkins, and Baum (2020) found that an increase in regulations regarding fire -
arm storage related to restricting minors’ access was associated with significantly reduced
workplace homicide rates. Specifically, they estima


d-access prevention laws reduce firearm homi-
cides or firearm assault injuries among young people.
Three studies examined the effects of
CAP laws on overall homicide rates or
other violent crime outcomes. Lott and
Whitley (2001) found that these


 CIs may be invalid; furthermore, no adjust -
ment was made for clustered standard errors, so the standard errors and significance values
reported in the paper were unreliable.
Hepburn et al. (2006) examined the relationship between CAP laws and un


me frame; thus, identification in both specifications was driven largely by changes
in state laws regarding negligent storage. The findings were generally confirmed in a second
analysis adding more control states (states without a change in CAP law


eover, both the child accessed  and child could access laws had only one state
implementing each law, with a full three years of pre- and post-implementation data available
in the study time frame, meaning that these effects may not be reliably est


d hospitalizations, DeSim-
one, Markowitz, and Xu (2013) found that
CAP laws significantly reduced unin-
tentional firearm injuries among those
aged 17 or younger and among those aged
18 or older.
Considering the relative strengths of
these stud


odels weighted by
state population and controlling for a large set of state-level time-varying covariates, state
fixed effects, national trends, and state-specific linear trends, the authors found uncertain
associations between CAP laws and the li


 indicate some issues with model overfit. Furthermore, a linear model does not appear to
correspond to the distributional features of the authors’ outcome variable, which limits the
inference that can be drawn from this single study.
Figure 17.5 d


l, Deborah, and Matthew Miller, “Reducing Suicide Without Affecting Underlying Mental
Health: Theoretical Underpinnings and a Review of the Evidence Base Lining the Availability
of Lethal Means and Suicide,” in Rory C. O’Connor and Jane Pirkis, eds


 4, 2002, pp. 407–416.
Cook, Philip J., Ariadne E. Rivera-Aguirre, Magdalena Cerdá, and Garen Wintemute, “Constant
Lethality of Gunshot Injuries from Firearm Assault: United States, 2003–2012,” American
Journal of Public Health , Vol. 107, No. 8, 2


isto, Aaron J., Katherine L. Kivisto, Erica Gurnell, Peter Phalen, and Bradley Ray,
“Adolescent Suicide, Household Firearm Ownership, and the Effects of Child Access Prevention
Laws,” Journal of the American Academy of Child and Adolescent Psychiat


ler, “Parent and Adolescent Reports of
Adolescent Access to Household Firearms in the United States,” JAMA Network Open , Vol. 4,
No. 3, March 9, 2021, e210989.Child-Access Prevention Laws317Schell, Terry L., Matthew Cefalu, Beth Ann Griffin, Rosan


t from specifying classes of people who are prohibited from possessing any type of fire -
arm, federal law imposes no restrictions on who may carry a concealed weapon in public,
although it specifically grants concealed-carry rights to active and re


2015 (Rowhani-The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies320Rahbar et al., 2017) and was more than 21.5 million in 2021 (Lott, Moody, and Wang, 2021),
with substantial variation across sta


llings, 2022; Donohue et al.,
2022). Differences in concealed-carry policies may also prompt changes in law enforcement
behavior, for example, through reallocating officer effort (e.g., processing permit applica -
tions). Changes in police expectat


me frame that found an increase in police
shootings that was associated with permitless-carry laws (Doucette et al., 2022).
3 Alaska, Arizona, Arkansas, Idaho, Kansas, Kentucky, Maine, Mississippi, Missouri, New Hamp -
shire, North Dakota, Oklahoma,


ide rates, but they found suggestive effects consistent with a reduction in total sui -
cide rates (see Figure 18.1). Nevertheless, the statistical model had an unfavorable ratio of
covariates to observations (less than one to eight), meaning the mo


 1977 to 2014 to evaluate the effects
of various firearm laws on suicide rates among adults aged 21 or older. Although the authors’
focus was on background check and waiting-period laws, they included model specifications
that additionally control


fects of shall-
issue laws on total suicide rates and firearm suicide rates. These estimates were associated
with an 83-percent and 90-percent probability that shall-issue laws increase total and firearm
suicides, respectively.
Figure 18.1 display


ts—one by the
National Research Council (NRC), a part of the National Academy of Sciences (NRC, 2004),
and one by the Community Preventive Services Task Force, established by the U.S. Depart-
ment of Health and Human Services (Hahn et al., 2005)—ev


ed that the findings in Lott (2000) persisted
even when analyzing the subset of counties with minimal error in crime statistics. After
reviewing this exchange, the NRC panel disagreed with Lott and Whitley that the origi -
nal effects reported by L


ies
Donohue (2003)a Mixed; effects were sensitive to model specifications and data
Helland and Tabarrok (2004) Increase in property crime, auto thefts, and larcenies
a These studies are treated in this report as being superseded by later studies by t


missing data changed abruptly in the
early 1990s, making data from the earlier part of the series not comparable with later data,
according to the National Archive of Criminal Justice Data (undated). Nevertheless, several
analyses have continued t


, reestimated their models after adding many more demographic control vari -
ables, robbery and assault rates, and a lagged outcome as a predictor meant to capture unmea -
sured state differences associated with crime rates. Moody et al. (2014) offer


ty-level demographic and
economic covariates, the authors found that shall-issue laws were associated with a signifi -
cant increase in firearm homicide rates. Specifically, after implementing these laws, counties
would be expected to see 1.07 time


may be unreliable.
Martin and Legault (2005) demonstrated that Lott (2000) used incorrect state crime rate
estimates that differed substantially from official FBI state estimates. They replicated Lott
(2000)’s model despite misgivings about its spe


g that homicides declined significantly after implementation of shall-issue
laws, but he did not provide test statistics or sufficient description to clarify what specific
effect was observed. The author also included coefficients and their statist


ng the model may have been overfit, and thus its estimates and
their apparent statistical significance could provide little generalizable information about the
true causal effects of shall-issue laws.
Gius (2014) examined the effect of shall-issue


(Aneja, Donohue, and Zhang, 2011). Foremost, the studies critiqued the decision to treat
models without state-specific trends as the preferred ones.10 Thus, Moody et al. (2014) reesti -
mated the hybrid models in Aneja, Donohue, and Zhang (2014),


ribed an assessment of the effects of shall-
issue laws that relies on constructing synthetic controls for each state that implemented a
shall-issue law. Synthetic controls are weighted combinations of states that never implemented
the law or that


me frame and estimating effects
for both the transition from no issue to shall issue and from may issue to shall issue, found
a suggestive effect that the transition from no-issue to shall-issue laws caused a reduction in
robbery rates but uncerta


ain analyses. However, even with the increased uncertainty around
the effect sizes, the estimated effects of shall-issue laws on total and firearm homicide rates
remained positive and statistically significant. Similar results were found by Fridel


tation) the effect was assessed. However, for both outcomes showing signifi -
cant effects, the study’s models had an unfavorable ratio of estimated parameters to observa -
tions (about one to three for murder rates and one to nine for robbery rates)


ffects, except when the outcome
was measured as police deaths per full-time equivalent officer; in that case, shall-issue laws
led to a negative shift in trend that was statistically significant. However, this model had an
unfavorable ratio of est


ault, and rape) using panel data from 1980 to 2000 for
189 large U.S. cities. The authors clustered the standard errors at the state level, addressed
coding errors in previous research, allowed for a time trend in the effect of shall-issue laws,
a


32-percent increase in the firearm homicide rate, while may-issue laws were associated with a
significant 33-percent reduction in the firearm homicide rate. (No estimates for unweighted
data with inter-censal years were provided.) The diametric fin


2  See, for instance, the Supreme Court’s decision in New York State Rifle and Pistol Association v. Bruen ,
2022, which classifies Hawaii as among the few remaining states with a may-issue licensing regime.
13  Nonurban areas  are defined as citie


sue laws led to significantly higher
rates of murder and assault; estimated effects on robbery rates were suggestive but also con -
sistent with an increase following the passage of shall-issue laws. However, the analyses had a
ratio of estimated p


ratio of estimated parameters to observations of less than
one to five and thus serious potential issues with model overfit. We exclude estimates from
Smith and Petrocelli (2019) because of the aforementioned concerns with their study results,
and


h richer evidence
base to draw on, including studies that raise serious methodological concerns and several
that did not raise as many concerns among our methodology review team. Therefore, to focus
this review on the best available evidence, we d


ive evidence for the effect of permitless-carry laws on total homicides .
Firearm homicides . Ten of the 22 studies examined the effects of shall-issue laws on fire -
arm homicides, one examined effects of the laws on fatal assaults of law enforcemen


two with data
extending past 2000 (Hamill et al., 2019; Kendall and Tamura, 2010), found only uncertain
effects of shall-issue laws on assault (Hamill et al., 2019; Kendall and Tamura, 2010; Helland
and Tabarrok, 2004; Plassmann and Whitley, 2003)


laws. In an
ordinary-least-squares regression controlling for arrest rates, population density, and socio-
economic characteristics, shall-issue laws had uncertain effects on unintentional handgun
deaths and suggestive effects consistent with incre


ed with blue squares indicate that methodological concerns are discussed in the
text. See Appendix B for details.
The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies
350Conclusions
We identified t


criminal activity or in which fewer than three of the
fatally injured victims were not related to the shooter (e.g., family, romantic partner). Finally, Blau, Gorry, Evidence for this
relationship is
inconclusive.Shall-issue concealed-carry
laws hav


impact of shall-issue concealed-
carry laws on a binary indicator for whether a mass shooting occurred in a given state-year.
Controlling for time-invariant state characteristics, national trends, and a host of other state-
level gun policies, as we


rry laws had an uncertain relationship
with the number of school shooting victims (see Figure 18.5). Given the relatively rare nature
of this outcome, these analyses may have been underpowered to detect an effect. These analy -
ses also did not inc


cealed-carry laws . We identified seven qualifying studies that examined the
effect of shall-issue laws on mass shooting outcomes. Lott (2003) found that shall-issue laws
were associated with significant reduc-
tions in multiple-victim shooting inc


round checks for handgun sales, long gun sales, and
the proportion of sales that are handguns. This study used linear regression models that
included state-level fixed effects and excluded the potentially problematic control for the
ratio of firea


outcomes. One study
(Ginwalla et al., 2014) found that allowing permitless carry in Arizona was correlated with
significant increases in NICS background checks relative to the national trend. One study
(Steidley, 2019) found that shall-issue and p


on Laws on Crime,”
International Review of Law and Economics , Vol. 47, 2016, pp. 76–83.
Bartley, William Alan, and Mark A. Cohen, “The Effect of Concealed Weapons Laws: An
Extreme Bound Analysis,” Economic Inquiry , Vol. 36, No. 2, 1998, pp. 258–2


 No. 2, June 2019, pp. 198–247.
Donohue, John J., Samuel V. Cai, Matthew V. Bondy, and Philip J. Cook, More Guns, More
Unintended Consequences: The Effects of Right-to-Carry on Criminal Behavior and Policing in
US Cities , Cambridge, Mass.: Nationa


, March 2019a, pp. 3–9.
———, “Using the Synthetic Control Method to Determine the Effects of Concealed Carry Laws
on State-Level Murder Rates,” International Review of Law and Economics , Vol. 57, March 2019b.
Goodman-Bacon, Andrew, “Difference-in-D


Justice , Vol. 24,
No. 1, 2008, pp. 4–17.
Lott, John R., Jr., “The Concealed-Handgun Debate,” Journal of Legal Studies , Vol. 27, No. 1,
January 1998a, pp. 221–243.
———, More Guns, Less Crime: Understanding Crime and Gun-Control Laws , 1st ed., Chi


egault, “Systematic Measurement Error with State-Level
Crime Data: Evidence from the ‘More Guns Less Crime’ Debate,” Journal of Research in Crime
and Delinquency , Vol. 42, No. 2, May 2005, pp. 187–210.
Moody, Carlisle E., “Testing for the Effects


nal Justice , Vol. 25, No. 1, 2009, pp. 67–88.
Rosengart, M., P. Cummings, A. Nathens, P. Heagerty, R. Maier, and F. Rivara, “An Evaluation
of State Firearm Regulations and Homicide and Suicide Death Rates,” Injury Prevention , Vol. 11,
No. 2, 2005


Smart, Rosanna, Terry L. Schell, Matthew Cefalu, and Andrew R. Morral, “Impact on
Nonfirearm Deaths of Firearm Laws Affecting Firearm Deaths: A Systematic Review and
Meta-Analysis,” American Journal of Public Health , Vol. 110, No. 10, October 2020


rt -
ment of Veterans Affairs (38 C.F.R. 1.218) or the U.S. Postal Service (39 C.F.R. 232.1). Two fed -
eral laws restrict guns in or around schools offering elementary or secondary education. The
Gun-Free School Zones Act of 1990 prohibits most fir


ese areas. There is debate
over the extent to which perpetrators target gun-free zones. One analysis of 133 mass shoot -
ing events between 2009 and 2016 found that 10 percent of incidents occurred in designated
gun-free zones (Everytown for Gun Sa


ina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Car -
olina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin,
and Wyoming. See Ala. Code 1975 § 13A-11-61.2; Alaska Stat. Ann.


as of restaurants (Miss. Code Ann. § 45-9-101(13); Mo. Rev. Stat. § 571.107.1(7)). Finally,
Illinois, Louisiana, and some other states prohibit open carry but allow concealed carry. Like Kentucky
and others, Illinois’s law does not apply in restaur


 Ida. Code Ann. § 18-3309; Kan. Stat. Ann. § 75-7c20 (concealed weapons shall not be prohibited
unless adequate security measures are in place to ensure that no weapons are permitted); La. Rev. Stat. Ann.
§  40:1379.3(c); Miss. Ann. Code §§ 97-37-7


32.1, Conduct on Postal Property.
Crime Prevention Research Center, “Updated: Mass Public Shootings Keep Occurring in Gun-
Free Zones: 94% of Attacks Since 1950,” June 15, 2018a.
Everytown for Gun Safety Support Fund, “Mass Shootings in the United S


onsult and Politico, 2022).
As discussed in Chapter Nineteen (on gun-free zones), two federal laws restrict who may
carry guns in or around schools offering kindergarten through grade 12 (K–12) education:
the Gun-Free School Zones Act of 1990 (18


nts between 2014
and 2018 that involved a firearm brought to a school by a law enforcement officer or that
involved a teacher improperly discharging or losing control of a weapon (Foley and Fenn,
2018). This compares with around 20 active-shooter


adults to carry weapons on K–12 campuses could create a new demand for specialized
training or practice. However, surveys suggest that most teachers are opposed to bringing
guns into schools, so uptake on teacher firearm certification may be low (B


 Code Ann. § 37.0811; Utah Code Ann. § 76-10-505.5;
Knicely, 2018; Wyo. Stat. Ann. § 21-3-132.The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies376nel but also no laws explicitly prohibiting it,


da. Code Ann. § 18-3302D(g); Miss. Code. Ann. § 97-37-17.Laws Allowing Armed Staff in K–12 Schools377Outcomes Without Studies Examining the Effects of Laws
Allowing Armed Staff in K–12 Schools
We did not identify any studies that met our inclusion c


search Center, April 25, 2019.
Marjory Stoneman Douglas High School Public Safety Commission, Initial Report Submitted to
the Governor, Speaker of the House of Representatives and Senate President , January 2, 2019.
Morning Consult and Politico, N


iety in general and individual stake -
holder groups in particular, and other issues central to the acceptability of any policy. These
scientific questions about what is true and knowable do not supersede questions of individual
rights or Second Am


effect. Even when multiple studies fail to find a significant effect, it is not correct that this
implies that the policy has no effect. Instead, the effects may simply be too small to reliably
detect, or the data available to assess the policy’s e


f such laws on
total suicides among young people. Looking across the columns, it is apparent that research
into five outcomes is either unavailable or almost entirely inconclusive. It is noteworthy
that three of these five outcomes—defensive gun u


CAP laws and the other two The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of U.S. Gun Policies386TABLE 21.1
Strength of Evidence Across Gun Policies and Outcomes
OutcomeMinimum Age
RequirementsProhibitions Associ


gistration Requirements Bans on the Sale of
Assault Weapons and
High-Capacity MagazinesBans on Low-Quality
HandgunsStand-Your-Ground LawsChild-Access Prevention
LawsConcealed-
Carry LawsGun-Free ZonesLaws Allowing Armed Staff
in K–12 Schools
Pu


talities and limited evidence that bans on high-capacity magazines reduce mass
shootings and fatalities.
i We found inconclusive evidence for the effects of may-issue, shall-issue, and permitless-carry laws on firearm purchases. Table 21.1—Continue


tively promote safe storage prac -
tices, particularly if storage devices (e.g., gun locks) are provided along with the counseling
(RAND Corporation, 2018, Chapter Twenty).
Conclusion 2.  There is supportive evidence that stand-your-ground laws are


e prevalence with which legal and illegal
carriage of firearms occurs in states with permissive concealed-carry laws. For instance,
Rowhani-Rahbar et al. (2017) found that in states with more-restrictive may-issue laws, only
9 percent of handgun o


categories of gun violence in the United
States. Half of all women who died by homicide in the United States in 2016 and for whom
relationship with the perpetrator was known were killed by a current or former intimate
partner (Ertl et al., 2019).


ter purchase or acquisition
of a firearm (Studdert et al., 2020). Although federal laws restrict the age at which young
people may purchase firearms from a federally licensed firearms dealer or possess handguns,
many states have adopted more-strin


 been reluctant to share those
records for use in the FBI’s National Instant Criminal Background Check System (NICS), the
federal database used for background checks. Although most states have laws allowing for the
voluntary sharing of some mental


arm reporting requirements or laws allowing armed staff in K–12 schools. Only
inconclusive evidence exists for the effects of gun-free zones; extreme risk protection orders
or “red-flag” laws; firearm safety training requirements; firearm sales rep


ating a
field that is growing but underdeveloped. Before 1996, the federal government supported a
modest program of research examining firearm violence and policy. In the early 1990s, the
CDC was sponsoring millions of dollars of research on firea


ing
cessation, HIV/AIDS, or traffic safety.
• Recommendation 10 . To improve the development of firearm violence prevention strate -
gies, the federal government should commit to an ongoing program of research fund -The Science of Gun Policy: A Cri


nform the trade-offs between this outcome and the potential public safety
benefits. Triangulating FBI information on justifiable homicides with other data sources that
capture aspects of defensive gun use (e.g., Gun Violence Archive, the National C


 the ways that gun owners store and use their weap -
ons. Therefore, gun ownership and use are the behaviors through which laws may affect such
outcomes as firearm suicide, firearm homicide, hunting and recreation, and firearm sales.
In the absence


were acquired, and other key details are omitted from these reports.
Although some researchers have been able to work with detailed trace data from individual
police departments or, rarely, whole states, trace data have not been available on a nati


ment agencies, NIBRS was designed to collect
incident-level information about crimes reported to police. It officially launched in the mid-
1980s, but by the early 2000s, only 16 percent of the U.S. population was served by a law
enforcement agency


(BJS) has explored options for generating such estimates through the National Crime Victim -
ization Survey (BJS, 2017b). In 2016, BJS began expanding the survey panel to generate reli -
able estimates for 22 states that account for 79 percent of t


a set must be purchased separately.
This expense represents a serious access barrier for most researchers interested in analyz -
ing state firearm injuries over time. Recently, however, the Healthcare Cost and Utilization
Project has released a red


estimates of the effects of gun
policies on various outcomes, and the computing power that researchers need to implement
the increasingly demanding modeling requirements has more than kept pace with the dif -
1 See, for instance, Healthcare Cost an


been found to contain errors that could affect results.
• Poorly justified models of the time course of a policy’s effects. Statistical models of the
effects of a policy impose assumptions about the period during which the effects of the
policy wi


e
more readily detectable effects on public safety, health, and industry outcomes. The United
States has a large stock of privately owned guns in circulation—estimated to be somewhere
between 265 million and 393 million firearms (Karp, 2018; Azrae


See Centers for Disease Control and Prevention.
Centers for Disease Control and Prevention, “Underlying Cause of Death, 2018–2020, Single
Race,” WONDER data system, undated-c. As of September 18, 2022:
https://wonder.cdc.gov/ucd-icd10-expanded.htm