(SACRAMENTO) —

Of the three states that recently expanded comprehensive background check (CBC) policies to include all gun transfers, including those among private parties, only Delaware showed an overall increase in firearm background checks. Washington and Colorado had no changes, which the study authors say suggests that compliance and enforcement were incomplete.

The study, which posted online October 6 in Injury Prevention, is believed to be the first to assess the association between CBC policy enactment and changes in background-check rates. It was conducted by the Violence Prevention Research Program at UC Davis and the Johns Hopkins Bloomberg School of Public Health.

Although 35 to 40 percent of all firearm transactions in the U.S. are between private parties, federal law does not require background checks for transactions among private parties. Without a background check, felons, those convicted of domestic violence crimes, and others who are prohibited from purchasing a firearm can avoid screening measures by purchasing firearms from sources other than licensed retailers.

“The overwhelming majority of all firearms used for criminal purposes, some 80 percent, are acquired through private party transactions,” said Alvaro Castillo-Carniglia, lead author of the study and a VPRP postdoctoral research fellow. “By expanding background checks to include private-party transfers, there is a higher chance that these policies will make it harder for felons and other prohibited persons to acquire firearms and commit violent crimes.”

“While it is too soon to measure the effects that comprehensive CBCs have on crime, we expected to see an increase in the number of background checks if states are complying with and enforcing the laws,” he said.

For the study, researchers estimated the difference in the monthly rate of background checks per 100,000 people for handguns, long guns and both types combined using data from January 1999 through December 2016. In Delaware, CBC enactment resulted in a 25 percent increase in background checks for handguns and a 34 percent increase for long guns. Washington and Colorado experienced no overall increase in background checks, though very limited data suggested that they may have experienced modest increases in background checks for private party sales.

In Washington, pro-firearm organizations, gun show organizers and others rallied for noncompliance. In Colorado some county law enforcement officials and retailers reportedly refused to enforce CBC laws and process background checks for private-party transactions.

“Unregulated firearm transactions are a public health problem,” Castillo-Carniglia said. “Comprehensive background check policies can play an important role in preventing the negative health and social consequences of violence.”

Other study authors include Rose M. C. Kagawa, Magdalena Cerdá and Garen J. Wintemute at UC Davis, and Daniel W. Webster and Jon S. Vernick at Johns Hopkins

The study, “Comprehensive background check policy and firearm background checks in three US states,” was funded by the Joyce Foundation (grant ID 15-36377) and the Heising-Simons Foundation (grant ID 2016-219). AC-C and RMCK were supported by the Robertson Fellowship in Violence Prevention Research. AC-C was also supported by Becas Chile as part of the National Commission for Scientific and Technological Research (CONICYT).

The UC Davis Violence Prevention Research Program (VPRP) is a multi-disciplinary program of research and policy development focused on the causes, consequences and prevention of violence. Studies assess firearm violence and the connections between violence, substance abuse and mental illness. VPRP is home to the University of California Firearm Violence Research Center, which launched in 2017 with a $5 million appropriation from the state of California to fund and conduct leading-edge research on firearm violence and its prevention.