Fatal shootings by police officers that are recorded on video often get national media coverage, fueling calls for reform, as we saw last week in the shootings of Alton Sterling in Baton Rouge, Louisiana, and of Philando Castile in Falcon Heights, Minnesota. And witnesses are filming more often: About 21 percent of fatal shootings by police officers in the first six months of this year were captured on camera, up from 16 percent at the same time last year, according to The Washington Post.

Police are embracing video, too — not from bystanders holding smartphones but from cameras that officers wear on their bodies. Police chiefs hope video will prove most of their officers are doing a good job and that cameras can help protect their force from violence, something that’s top of mind after the sniper attack in Dallas last week that killed five officers and other subsequent attacks on law-enforcement officers. Reformers and police officials like the clarity that can come with video evidence and the potential to reduce violence by introducing more cameras to interactions between police and the public.

But are body-worn cameras really the best way to prevent shootings involving police officers? Even when an officer is wearing one, a body camera doesn’t always capture clear footage of violent encounters. The cameras worn by the officer who shot Sterling and by his partner became dislodged during their altercation with him, according to a department official; the video that helped launch a federal investigation wasn’t taken by officers. The evidence we have that cameras can prevent shootings is indirect — it looks at general uses of force, not specifically fatal ones — and comes from just a handful of departments. And one study found that cameras don’t prevent assaults on officers; instead, officers wearing cameras appear to be assaulted more often than those who don’t.

“It’s a race between the evidence and the policy that we’re just about keeping up with,” said Alex Sutherland, a research leader at Rand Europe, a policy research institute that has studied body cameras’ use by several police departments.

Body cameras are lightweight devices affixed near the collar of an officer’s shirt or on his or her headgear, set to record from the officer’s point of view and provide video beyond what is already available from security cameras and squad car dash cams. Wearing one, the theory goes, can help defuse a tense situation because officers will know that their behavior is being recorded for potential scrutiny, as will the civilians involved. If a violent encounter does happen, the footage can be used as evidence. And it can be used to train officers to handle tense situations better by doing what fighter pilots and athletes do: review tape.

Police officers in the U.S. shoot and kill about a thousand people each year, accounting for roughly 3 percent of all gun deaths.1 Many people who were fatally shot by police are young black men, and around 16 percent of them are unarmed. These striking figures, and the low number of prosecutions of police officers who shoot and kill, have sparked protests in cities nationwide and calls for reform.

More than reduce police shootings, several police officials said, they think body cameras will help departments dismiss most civilian complaints about officers as unwarranted. When there’s video evidence, “99 percent of the time, the video is on the officer’s side,” said Dave Bertini, police commander in Menlo Park, California.

Several Bay Area departments’ use-of-force incidents declined sharply after body cameras were introduced. Oakland was one of the earliest and biggest adopters, adding more than 700 cameras since 2009. Use-of-force incidents have declined by more than 75 percent, according to the department’s stats. (The scandal-ridden department now faces a fresh crisis of legitimacy over corruption and sexual misconduct.)

And in Menlo Park — a smaller and wealthier city than Oakland with a lower crime rate — there have been fewer use-of-force incidents combined in the two years since officers started wearing body cameras than in the year before that. Bertini thinks that if every department in the country started using the cameras, there would be a “dramatic decrease” in use of force. But he’s not sure cameras are the sole reason for the drop in his department. Crime rates also have fallen. “You can’t point to just one thing,” he said.

The handful of studies of body cameras’ effectiveness in reducing violence between officers and civilians don’t all agree. Sutherland and his colleagues wrote one of the first papers on body cameras, a study of the department in Rialto, California, that helped spur widespread adoption of cameras. They found that use of force was more than twice as frequent among officers not wearing cameras as among those who wore cameras.

A subsequent study in Orlando showed similar results. The researchers are now working on a similar experiment in Tampa. “I think, generally, cameras are going to de-escalate and reduce most serious uses of force, such as firearms,” said Wesley Jennings, one of the researchers and a criminologist at the University of South Florida.

But in May, some of the Rialto researchers released a pair of studies of eight departments, including Rialto and Ventura in California, that contradicted their earlier finding. It showed that on average, body cameras didn’t reduce use of force by officers. And officers wearing cameras saw a 15 percent increase in risk of assault compared to officers working shifts that didn’t use the cameras. The researchers think that cameras might make officers less assertive and therefore more vulnerable to assault, or that by capturing every interaction, they might give officers the confidence to document minor assaults they previously would have let go.

Sutherland and Jennings said more research is needed to know whether body cameras can prevent the roughly 39 gun homicides of police officers each year.2 It’s unclear, for instance, whether their efficacy depends on officers’ telling people that they’re on camera. Jennings called it a “logical assumption” that cameras would reduce assaults on officers — except in the case of people who wouldn’t care about the repercussions of being on videotape, he said, or who attacked from a distance beyond the range of cameras, as in the sniper attack in Dallas.

Even if a study shows that cameras prevent violence in one place, they might not work in another. “The biggest problem law enforcement has had is studies that can be replicated from community to community,” said David Rausch, chief of the Knoxville police department, which isn’t using body cameras. “You’re dealing with people, so replication can be hard to do.”

And the country’s law-enforcement apparatus is too decentralized for any one department to be able to demonstrate any meaningful success reducing the national number of fatal shootings involving police officers. Most of the country’s 18,000 law-enforcement departments aren’t involved in any fatal shootings in a typical year, so even if the cameras worked perfectly for one such force, it wouldn’t do much to reduce the national death toll.

Sutherland and his colleagues are still running an experiment in 20 other cities. “Our results could change completely” again, he said.

Police officers are rarely charged for fatal shootings, but when it happens, video evidence often is critical. For that reason, some advocates for reducing police violence cautiously back body cameras’ use, though with major concerns about privacy — of civilians and of officers. Policies vary widely by state on whether footage can be accessed like other government records. Other concerns include how police use the footage and how footage can traumatize viewers.

When Segun Idowu helped found the advocacy group Boston Police Camera Action Team in 2014, the only academic research supporting cameras was the Rialto study. “We knew from the beginning it was very flawed,” Idowu said. Why would the experience of a California city of 100,000 residents translate to Boston? But the use of cameras seemed inevitable, Idowu said, so members figured they might as well have a say in how they’re used. He still isn’t exactly an evangelist for cameras. “At the end of the day, I think they are a positive if used correctly with the right policies,” he said.

Advocates say details such as whether officers must keep filming throughout encounters, and whether they are punished if they don’t, are critical to the cameras’ success. “Body cameras won’t help (and can be harmful) without strong policies in place to ensure accountability,” said Samuel Sinyangwe, co-founder of Campaign Zero, a group that strives to reduce police violence.

Sinyangwe and Idowu think it’s critical that officers don’t get to review footage before writing incident reports, especially after shootings, so they can’t try to spin the footage to show their action in a favorable light.

The cameras raise other concerns: the cost of storing and logging video and the potential for misinterpretation of footage. But they remain a popular policy aimed at reducing police violence among leaders looking to restore the public’s trust in police.

“We in the public have put law enforcement on notice,” said Steve Tuttle, co-founder of Taser International, the leading body-camera vendor in the U.S. Police officers “are under a microscope. These are tools that will help them be in that microscope and answer questions that couldn’t be answered without video.”

President Obama announced plans in 2014 to fund up to 50,000 of the cameras. In fiscal year 2015, Justice funded 21,000 cameras for 73 agencies. Taser International signed body-camera deals for $52.1 million in the first three months of this year, nine times the company’s sales in the equivalent period of 2014. And that’s just scratching the surface.

More than 95 percent of departments that responded to a survey of the Major Cities Chiefs Association and Major County Sheriffs’ Association last summer said they at least had plans to introduce cameras to their forces. Hillary Clinton, the front-runner to succeed Obama, wants every police department in the U.S. to outfit officers with cameras to “help protect good people on both sides of the lens.”

Stuart Cameron, chief of the Suffolk County, New York, department, is one of a number of police officials more confident in the cameras’ ability to resolve civilian complaints “a little more conclusively” than to reduce use of force. His department is one of the biggest in the country that hasn’t signed a deal for body cameras, though Cameron would like to run a pilot project.

“I’m not necessarily convinced,” Cameron said. Like many cops, he trusts other ways to prevent violence between police and the public, such as training in de-escalating tense encounters or providing officers with less lethal weapons such as pepper spray.

This article is part of our project exploring the more than 33,000 annual gun deaths in America and what it would take to bring that number down.


  1. There are no reliable government counts of police killings. Last year, The Guardian and The Washington Post tried to count all the fatal shootings by police. The Guardian counted 1,019, and the Post, 990. Three other, crowdsourced efforts — Fatal Encounters, the Gun Violence Archive and Mapping Police Violence — all had slightly higher counts than the two news media projects did. Based on the discrepancy between these counts and the media’s, it’s likely that had The Guardian and Washington Post been counting in 2014, they would have tallied about 980 fatal police shootings. (Our audit of another crowdsourced effort lends support for the validity of crowdsourcing: We found that the vast majority of cases would be considered police killings by most observers.) Some researchers think that even these crowdsourced efforts likely are missing some cases, so 1,000 may be an underestimate.

  2. That’s based on the FBI’s annual Law Enforcement Officers Killed and Assaulted reports for 2012, 2013 and 2014.

Carl Bialik was FiveThirtyEight’s lead writer for news.