In 2004, off-duty and on-duty police officers in Milwaukee brutally beat Frank Jude, a black man — breaking his nose, stuffing pens into his ears to the point that they bruised and bled, and leaving him naked from the waist down in a pool of his own blood afterward, all because they believed he stole a police badge.

As brutal as the attack was, new research suggests that it didn’t just harm Jude and lead to the terminations, discipline, and convictions of several officers involved. It also may have made led to more unchecked crime — by scaring black residents from calling 911.

The study, from sociologists Matthew Desmond of Harvard, Andrew Papachristos of Yale, and David Kirk of Oxford, took a look at the number of police-related 911 calls after Jude’s story broke in the local newspaper.

The study found that 17 percent (22,200) fewer 911 calls were made in the following year compared with the number of calls that would have been made had the Jude beating never happened. More than half of the effect came from fewer calls in black neighborhoods. And the effect persisted for more than a year — after officers were punished, indicating that the problem was the beating itself and not just holding individual officers accountable.

The study only found a correlation, not causation. So within just this data, it’s possible that something else happened — such as staffing or administrative changes in how 911 calls were handled — that coincided with the “Jude effect” and led to fewer calls.

But the researchers also found fewer 911 calls than projected in Milwaukee following two other high-profile police events: the local police beating of Danyall Simpson and the New York City police shooting of Sean Bell. That suggests that the effect can come from high-profile police events, even national ones.

The researchers did not, however, find a drop in 911 calls after the Oakland, California, police shooting of Oscar Grant — indicating some national cases may not have as much of an effect on 911 calls, particularly as high-profile local cases.

Still, the study’s findings just seem like a bit of common sense: After police officers receive negative attention for excessive force, or something else that’s similarly bad, the people they’re policing will typically trust them less. And with less trust likely comes less willingness to call the police for help.

But there’s another problem: Reduced trust could also lead to more unchecked crime and violence.

“An important implication of this finding is that publicized cases of police violence not only threaten the legitimacy and reputation of law enforcement,” the researchers write, “they also — by driving down 911 calls — thwart the suppression of law breaking, obstruct the application of justice, and ultimately make cities as a whole, and the black community in particular, less safe.”

Loss of trust in police can lead to more unabated crime and violence

Police legitimacy is crucial to stopping and preventing crime. The concept is simple: If people don’t feel they can trust the police and criminal justice system to prevent and solve crimes, then they are more likely to take the law into their own hands — and sometimes that will lead to them acting violently to solve interpersonal disputes.

This concept has been demonstrated in several studies, as well as brilliantly argued by journalist Jill Leovy in her book Ghettoside.

So loss of trust in the police can lead to more crime and violence.

“This is what folks who rail against the focus on police violence — and pull up against that, community violence — get wrong,” criminologist David Kennedy previously told me. “What those folks simply don’t understand is that when communities don’t trust the police and are afraid of the police, then they will not and cannot work with police and within the law around issues in their own community. And then those issues within the community become issues the community needs to deal with on their own — and that leads to violence.”

Loss of trust in the police can lead to more crime and violence

Take 911 calls as an example. If someone calls 911, he or she can possibly prevent a crime — get a domestic abuser locked up before he kills someone, stop a robbery, burglary, or murder before it’s complete, and so on. But if someone isn’t willing to call 911, the police aren’t going to be able to intervene.

But even if people don’t call 911, those crimes will still happen, and individuals will still have to deal with those crimes — just on their own terms. That may mean shooting the burglar who breaks into your house. Or it could mean shooting the man who beat a woman you’re friends with. Or it could mean killing someone as payback after he killed your brother. When people can’t fall back on the criminal justice system for help, they’re more likely to resort to these methods.

As Leovy put it in Ghettoside, “Take a bunch of teenage boys from the whitest, safest suburb in America and plunk them down in a place where their friends are murdered and they are constantly attacked and threatened. Signal that no one cares, and fail to solve murders. Limit their options for escape. Then see what happens.”

Indeed, the Milwaukee study speaks to this issue: As 911 calls dropped, researchers also found a rise in homicides. They note that “the spring and summer that followed Jude’s story were the deadliest in the seven years observed in our study.” They don’t prove a cause-and-effect chain here — but it’s certainly suggestive, given what we know about the effect of police legitimacy on crime.

Addressing racial disparities in police use of force and police brutality more broadly, then, isn’t just about resolving an injustice — although that’s obviously a worthwhile goal on its own — but also about making American communities safer.