Police shootings of civilians are more likely in states with high rates of gun ownership, according to a new study by researchers from Northeastern and the Harvard T.H. Chan School of Public Health.

“The take-home message from the study is that when people live in places where guns are more prevalent, the police officers are more likely to shoot and kill them,” said co-author Matt Miller, professor of health sciences at Northeastern and co-director of the Harvard Injury Control Research Center. “The relationship is pretty strong.

“The two factors that we looked at that were most strongly predictive of whether a citizen would be legally shot and killed [by police] were the overall rate of violent crime in that state and the overall rate of civilian firearm ownership.”

The researchers analyzed data from The Washington Post’s “Fatal Force Database,” which catalogues the number of civilians shot and killed by police in the line of duty. They found that police shootings for the years 2015 to 2017 were 40 percent more likely to occur in states with more guns. People who lived in the 10 states with the most guns were 3.6 times more likely to be involved in fatal police shootings than if they lived in the five states with the fewest guns.

Studies of police shootings in recent years have tended to focus on racial disparities, the researchers noted. This report approached the issue from a different point of view: It is the first to look at firearm prevalence in attempting to explain why some states experience more police shootings than others.

As a first step along this new line of inquiry, the report didn’t examine how issues of race and mental health influenced confrontations between civilians and police. It may open the door for researchers to take a deeper look at the extent to which a higher availability of guns leads to greater tension for law enforcement.

“When police are involved in an encounter where guns are more prevalent in general, I wouldn’t be surprised that their level of anxiety were heightened,” Miller said. “But we don’t know that from the study.”

Previous research has shown that police are also more likely to be killed in states with higher levels of gun ownership, he added.

Miller teamed with Harvard researchers David Hemenway, Deborah Azrael, and Andrew Conner, who was a former student of Miller’s at Northeastern. Variation in Rates of Fatal Police Shootings across US States: the Role of Firearm Availability, published earlier this month in the Journal of Urban Health, was adjusted for rates of violent crime in each state and other factors.

For media inquiries, please contact Shannon Nargi at s.nargi@northeastern.edu or 617.373.5718.