Joshua Lott / Reuters

In the latest shooting to outrage the nation, Amber Guyger, an off-duty Dallas police officer, claims she walked into the wrong apartment in the building where she lives and pointed her gun at Botham Shem Jean, thinking that he was an intruder. Guyger then shot and killed Jean. By all accounts, Jean was doing nothing wrong. He was simply at home minding his own business.

As a country, we used to ignore police crime. That changed in August 2014, when an officer in Ferguson, Missouri, killed Michael Brown, an unarmed teenager. Yet the government hasn’t caught up to public interest. Former FBI Director James Comey went so far as to say in 2016 that “Americans actually have no idea” how often police use force, because the federal government has not bothered to collect the relevant data. Although the FBI now plans to track the number of people killed by police across the United States, by early 2018 only 1,600 of the more than 18,000 state and local law-enforcement agencies had agreed to submit data for the project. And initial data collection had not yet commenced.

More than a decade ago, I decided to start my own research database on crime by law-enforcement officials. It’s expansive. It includes information on more than 12,000 policemen and policewomen arrested for one or more crimes since 2005. Some of the crimes are serious felonies, such as robberies, rapes, and murders. Many are less serious misdemeanors, such as disorderly conduct. (A searchable version of the database is publicly available for the years 2005 to 2013.) My student research assistants use media reports and court records to track incidents and outcomes—that is, whether the officers are found guilty and what consequences they face, if any. The database isn’t comprehensive, but it’s better than nothing—which is what the federal government offers.

A prominent policing scholar once wrote that “law enforcement is exempt from law enforcement,” meaning that police officers do not like to arrest other police officers. In my experience, most people assume that police crime is rare. Occasionally they read an article in their hometown newspaper or watch a story on the evening news about a local police officer who’s been charged with a crime. It seems unusual. What they don’t realize is that, every night, people across the country encounter similar stories. Only when we aggregate police crime from all over the United States does the extent of the problem become apparent.

So, what are we dealing with?

More than 900 police officers are arrested each year, and roughly 60 percent of all crimes for which police are arrested occur while they’re off duty, as Guyger was when she shot Jean. Nationwide, there were 5,475 cases of officers arrested for off-duty crimes in the years 2005 to 2013. (That case number includes officers arrested more than once during the study years.)

More than half of off-duty crimes are violent (52 percent), and a large number of them are alcohol-related offenses (42 percent). Off-duty police officers commonly carry a handgun, so perhaps it’s not surprising that a significant number of the cases in my database (11 percent) involve an officer who used a firearm in the commission of an off-duty crime. In some of the cases, an off-duty officer used a police-issued firearm to settle an otherwise nonviolent dispute with family members, friends, or neighbors.  

More police officers are arrested each year for murder or manslaughter resulting from off-duty shootings than from on-duty shootings. That of course doesn’t mean that police are more likely to shoot someone while off duty, just that off-duty shootings are more likely than on-duty shootings to be considered criminal.

In the years 2005 to 2013, there were 56 police officers charged with murder or manslaughter resulting from an off-duty shooting, and 41 (73 percent) were convicted. During the same nine-year period, there were just 41 officers charged with murder or manslaughter resulting from an on-duty shooting, and only 21 (51 percent) were convicted.

The data suggest that we should discourage off-duty police from carrying guns. I used to work in law enforcement, and I know from experience that officers are socialized into a police subculture that is built around an us-versus-them mentality: Everyone but “us” is a potential threat. And police can’t just turn off this way of seeing when they go off duty. Perhaps that’s natural, and there’s nothing we can do about it—but our environment would be a lot safer for “them,” for the Botham Shem Jeans of the world, if cops seeing red didn’t carry guns.

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