A study released Thursday finds that states with higher rates of private gun ownership have significantly higher rates of law enforcement homicides, or the murder of an officer in the line of duty.

The study, lead by Dr. David Swedler, an occupational injury researcher at the University of Illinois, shows that states in the top five for gun ownership had three times the rate of law enforcement homicides, per capita, than states in the bottom five for gun ownership. Of the homicides examined in the study, 92 percent were committed with a firearm.

“We know that firearm ownership at the state level is associated with many types of homicides: stranger homicide, intimate-partner homicide, and general homicide rates,” Swedler tells The Trace. And, he adds, since police officers are most commonly killed by firearms, “we were wondering if firearm ownership was associated with the homicide of officers.”

Alaska, Montana, Arkansas, Alabama, and Mississippi were in the highest quintile for both law enforcement homicides and gun ownership rates, while Massachusetts, Rhode Island, Connecticut, New York, and New Jersey were in the lowest quintile for both groups.

The study examined 782 law enforcement homicides between 1996–2010, using data provided by the Federal Bureau of Investigation. Combined, all 50 states and the District of Columbia averaged slightly over 15 law enforcement homicides during the study period.

Swedler and his colleagues looked for relationships between law enforcement homicides and population ages, median income, divorce rate, racial makeup, violent crime rate, and private firearm ownership, each time controlling for other factors. No factor studied, including violent crime rate, had a significant statistical correlation to the murders of police officers — except for statewide rate of gun ownership.

Megan Strand/UIC
Megan Strand/UIC

The study found a mean firearms ownership rate of 38 percent of U.S. households, while average ownership per household swung from 4.8 percent (District of Columbia) to 62 percent (Wyoming).

To determine rates of gun ownership, the researchers used the Behavior Risk Factor Surveillance System. The survey simply asks respondents if there is a gun in their homes — not what kind, if it’s legal, or anything else more specific. There is no federal gun registry, and the vast majority of states do not have their own registries, either, so the BRFSS is considered to be one of most accurate data sets available, according to Swedler and other researchers.

FA ownership graph

Swedler says that the relationship between gun ownership and law enforcement homicides is most apparent in domestic violence incidents. “We found in a previous study that domestic violence calls are one of the leading situations in which the officers are killed,” he says. “In a state where there’s more guns, officers are more often going to be showing up at domestic violence scenes where guns are present, as opposed to officers showing up at domestic violence scenes in states with lower rates of gun ownership.”

The study only demonstrates a correlation between gun ownership and homicides of law enforcement officers. It does not show causation, and as Swedler readily admits, “It’s not a one-to-one all the way across.” Each of the states with a higher rate of gun ownership does not necessarily have a higher rate of per-capita officer homicides. But a general pattern emerges, at a rate of three to one, as you move to the extremes — the states with the most and least guns. The BRFSS is also a self-report survey, so it does have limitations, although the researchers also utilized the Center for Disease Control’s statistics on firearm suicides in each state — a common proxy for gun ownership — and found a similar relationship to officer homicides.

Molly Simmons of the Johns Hopkins Bloomberg School of Public Health and Francesca Dominici and David Hemenway of the Harvard School of Public Health contributed to the study.

Swedler emphasizes that he approached the issue from the viewpoint of occupation health: In other words, the study is meant to help protect cops on the job. “I’m not coming to take anybody’s guns,” he says. “I’m sure people are going to hate this analysis, and they’re going to say, ‘Oh, he’s biased,’ but I would say to that: Listen. If you are someone who wants to protect the lives of police officers, please consider the laws about guns in your state.”

[Photo: Flickr user Jorge Miente]