State Intimate Partner ViolenceRelated Firearm Laws and Intimate Partner Homicide Rates in the United States, 1991 to 2015

Every year, more than 1800 persons in the United States are killed by their intimate partners, and approximately 50% of these homicides are committed with firearms (1). Approximately 85% of victims of intimate partner homicide (IPH) are women, and IPH accounts for nearly 50% of all homicides involving women in the United States each year (2, 3). Several studies (47) have shown that in situations of intimate partner violence (IPV)which may include physical violence, sexual violence, stalking, and/or psychological aggressionabusers' access to firearms increases the risk for IPH as much as 5-fold (5). Because of the association between firearm access and IPH, regulating the possession of firearms by IPV offenders is one approach to reducing IPH (3, 68). Federal legislation enacted in the United States in 1968 prohibited firearm possession by persons convicted of an IPV-related felony (9). This legislation was augmented in 1996 to extend the prohibition to those convicted of an IPV-related misdemeanor (10). In addition, the 1994 Violence Against Women Act barred firearm possession by persons subject to permanent IPV-related restraining orders (11). However, there is limited federal capacity or willingness to enforce these restrictions. Therefore, several states have enacted their own statutes to mirror these federal laws and explicitly authorize state officials to enforce the restrictions curtailing IPV perpetrators' possession of firearms (we refer to these as possession laws). However, a substantial loophole in the federal statute limits the ability of states to enforce these laws, even if they have codified the federal statute into their own laws. Although the federal statute prohibits certain IPV offenders from possessing firearms, it does not explicitly require them to surrender guns already in their possession (12, 13). In other words, in some states, a person may technically be prohibited from possessing a firearm, but it is up to the person to go to a police station to relinquish the weapon. Without statutory authorization, law enforcement cannot confiscate the firearms. This loophole has been termed the relinquishment gap by the Law Center to Prevent Gun Violence (14). As the Law Center stated in its recent report on this loophole, One of the most glaring gaps in the nation's gun lawseven in states with the strongest gun laws in the country, like Californiais the lack of an effective firearm relinquishment policy. Few state legislatures have taken any meaningful steps to actually enforce their criminal gun restrictions by ensuring that armed offenders give up their firearms after they are convicted of serious crimes (14). Recently, however, some states have taken steps to enforce their gun restrictions by going beyond federal law. One way that some states have done this is by enacting legislation that explicitly requires persons prohibited from possessing firearms due to an IPV-related misdemeanor or restraining order to surrender firearms already in their possession (we refer to these as relinquishment or surrender laws) (14). These laws typically enhance enforcement by putting offenders on official notice that surrender of their firearms is required and by specifying a time by which the transfer must take place. For example, California law requires that when a court issues an IPV-related restraining order, it orders respondents to surrender all firearms in their possession within 24 hours by transferring them to a law enforcement official or a federally licensed gun dealer (15). As of 2016, 11 states explicitly required persons convicted of an IPV-related misdemeanor to surrender their firearms after conviction, and 15 states explicitly required persons subject to an IPV-related restraining order to surrender their firearms for as long as the order is in effect (14). A second approach that some states have used is requiring law enforcement officials to remove firearms from the scene of an IPV incident. A third approach involves extending the prohibition of firearm possession to persons convicted of stalking. We are aware of only 3 studies that have evaluated the effect of state firearm policies on IPH rates (1619). These studies were limited because they used data from 2003 or earlier and had little power to detect an effect of IPV-related firearm policies because so few states had enacted such policies. Most important, at the time of these studies, few states had enacted laws that required IPV offenders to surrender firearms already in their possession, although 16 states had adopted a relinquishment law by 2013. The number of state IPV-related firearm laws has increased sharply since 2003, partly in response to the reauthorization of the Violence Against Women Act in 2005. A new provision made Violence Against Women Act grants conditional on state courts' informing convicted IPV offenders of the federal and any state restrictions on firearm ownership. This study builds on and extends previous studies in 2 key ways. First, our data include homicide rates and state laws over a much longer and more recent time frame (1991 to 2015). Second, we drew data from the most comprehensive coding of state IPV-related laws to date, paying particular attention to relinquishment provisions that might be critical to the larger policy goal of restricting firearm possession by potentially dangerous persons. Methods Design Overview We conducted a panel study to examine the association between state IPV-related firearm laws and total and firearm-related IPH rates between 1991 and 2015. The panel consisted of state-level predictor and outcome variables for each of the 50 states during each of the 25 years. The outcome variable was the state-specific IPH rate in a given year. Four categories of laws were considered: 1) prohibition of firearm possession by persons convicted of an IPV-related misdemeanor, with or without a relinquishment requirement; 2) prohibition of firearm possession by persons subject to an IPV-related restraining order, with or without a relinquishment requirement; 3) laws authorizing removal of firearms from the scene of a domestic violence incident; and 4) prohibition of firearm possession by persons convicted of stalking (Table 1). We also examined whether laws in the first 2 categories included a mechanism to ensure that persons surrender firearms already in their possession. Because we used secondary data sources without personal identifiers, the Institutional Review Board of Boston University Medical Center deemed this not to be human subjects research. Table 1. Differences in IPH Rates Associated With 4 Categories of IPV-Related Firearm Laws Considered Individually* Measures and Data Sources Outcome Variables Annual Firearm, Nonfirearm, and Total IPH Rates, by State. The only national data source that records homicide victimoffender relationships is the Supplementary Homicide Reports (SHR) of the Federal Bureau of Investigation's Uniform Crime Reports (2023). State and local law enforcement agencies report homicides to the Federal Bureau of Investigation on a monthly basis. Data were provided for each of the 50 states for the entire study period, with the exception of missing data for 23 stateyear combinations. Thus, the final sample size was 1227 out of 1250 possible observations. The SHR victimoffender relationship categories include spouses, common-law spouses, former spouses, and dating partners, but former dating partners are not specifically categorized (24). This prevented us from assessing the effect of IPV-related firearm laws on abuse of noncohabiting dating partners, which is underreported in the SHR because these cases are often not classified as IPH (24). Missing Data on VictimOffender Relationship. The SHR is limited by missing data on the victimoffender relationship in approximately one third of homicides. Fox and Swatt developed a multiple imputation approach for these missing data that is generally viewed as the strategy of choice (25). The imputation procedure attempts to ascertain the likely victimoffender relationship using known variables about the case and the observed association of those variables with the victimoffender relationship in cases where this relationship is clear. Fox provided us with multiply imputed files covering 1990 to 2015 (26). In our prior work, we showed that regression results obtained using the imputed data are similar to those obtained using only cases in which the victimoffender relationship is known (27). Nevertheless, we conducted analyses using both the imputed and nonimputed data to ensure that the imputation process did not alter the findings. The correlation between imputed and nonimputed IPH rates was 0.93. Main Predictor Variable Using searches conducted with the WestlawNext and HeinOnline legal resources, with laws then collected from state legislature Web sites, Everytown for Gun Safety developed a database of state IPV-related firearm laws over time (28). Using this database, we coded 4 categories of laws and their operative provisions (a total of 6 variables) as present or absent for each state during each of the 25 years from 1991 through 2015 (Appendix Table 1). Data on these provisions for all 50 states for 2015 are shown in Appendix Tables 2 and 3. State laws on IPV-related felonies were not included in our analyses because most states have procedures in place for the surrender of firearms by persons convicted of felonies. Appendix Table 1. IPV-Related Firearm Law Provisions Coded Appendix Table 2. Firearm-Related and Total IPH Rates in 2015 and Total Number of IPV-Related Firearm Law Provisions in 2014 Appendix Table 3. Status of Selected IPV-Related Firearm Laws, by State, 2015 Control Variables We accounted for secular trends in homicide rates by including year fixed effects. To account for dynamic effects and to address the potential problem of omitted-variables bias, we included the lagged IPH rate (that is, the rate in the pre