An NYPD officer wears a body camera. (REUTERS/Shannon Stapleton)

Nancy La Vigne is director of the Justice Policy Center at the Urban Institute. She is leading a study on the impact of body-worn cameras in three U.S. cities.

Body cameras aren’t new, but since the spate of high-profile violent encounters between police and unarmed citizens — Michael Brown, Chris Lollie, Eric Garner, Marlene Pinnock and others — they’ve been at the center of our debate about how to reduce these types of incidents. Police in Washington and New York City have instituted body-camera pilot programs, Maryland Gov. Larry Hogan signed a law last month enabling their use in his state and Sen. Tim Scott is making a push for body-camera funding in Congress. These efforts can be effective, but they’re not a cure-all. Here are five myths about the power of body cams.

1. Body cams capture the whole story.

When Ferguson, Mo., police started wearing body cameras after the shooting death of Michael Brown, then-police chief Tom Jackson proclaimed “the quality is good” with regard to the images his officers were recording. Last year’s video of an Albuquerque police officer firing eight shots at a suspect is seared in the public conscience — it shows officer Brian Pitzer shooting Joaquin Ortega as he fled. But rarely do body-worn cameras capture police-citizen interactions with such a high degree of clarity.

Body cams have the same limitations as stationary public surveillance cameras, or CCTV (closed-circuit television), including the camera’s viewshed, available lighting and low-visibility weather conditions. Another factor that compromises precision is the camera-wearer’s movement, which can mask or distort incidents on playback. In interviews with police investigators as part of a 2011 Urban Institute evaluation of CCTV use in three U.S. cities, my colleagues and I found that poor-quality footage was a significant barrier to the technology’s utility.

And cameras capture different details depending on where they are positioned on the officer, who typically has discretion in choosing whether the camera is mounted on the head, chest or shoulder. The AXON camera produced by Taser, by far the largest vendor of body cameras in the country, offers “multiple on-body mounting positions.” The model policies promoted by the Justice Department are silent on the topic of where the camera sits.

Like fixed surveillance cameras, body-worn lenses capture only the perspective of the officer and the direction in which he or she is facing, leaving out such critical context as the presence and actions of others outside the frame. They rarely capture the proverbial “smoking gun” and thus are unlikely to replace witness testimony. In many cases, they’re a complement to it at best.

2. They’re filming 24/7.

Last year, Chuck Wexler of the Police Executive Research Forum described a “brave new world” of body-worn cameras in which officer privacy could be compromised: Are the cameras still rolling when they eat lunch? Or take bathroom breaks? But in practice, officers have considerable discretion in choosing when to turn their cameras on, which can affect what they capture and how effective the footage will be.

There is ample opportunity for officers, intentionally or not, to fail to activate their cameras in a timely manner. Take the case of the Mesa, Ariz. police department, which found that giving officers discretion on the issue resulted in a 42 percent reduction in video files generated monthly. That saves data storage, but it also means cameras might not be turned on during the moments that lead up to violent interactions. If police departments and the public want a visual record of all interactions, from start to finish, between citizens and cops, municipalities have to mandate it.

3. Video will root out bad cops.

When the Denver police started phasing in body cameras, chief Robert White said that citizens in his city “should know officers are being held accountable” and that “the only officers who would have a problem with body cameras are bad officers.” The presumption being that the introduction of body cams means bad cops will eventually be off the street. But not always.

Police unions have had a say in whether law enforcement agencies adopt body cameras; in Washington and elsewhere, there’s debate over proposed policies that would bar the review of footage for the explicit purpose of identifying misconduct. Similarly, guidance from the Police Executive Research Forum advises that supervisors should restrict reviewing of footage to training purposes, a documented pattern of abuse or misconduct or in response to citizen complaints or other precipitating acts.

And while CNN’s Mark O’Mara — the attorney who represented George Zimmerman — argues that “people act better when they know they’re being watched,” we’ve learned from the Eric Garner case that police-citizen interactions can turn deadly, even when cameras (in that case, mobile-phone cameras) are rolling.

4. Public record means public access.

Police are civil servants, their body cams are public equipment and the videos they record are technically public records. But that doesn’t mean the public will get immediate or unlimited access to the footage these cameras produce. While public demand for the release of video footage is high, meeting that demand is costly because it requires redaction (removing parts that aren’t for public consumption) first. D.C. police chief Cathy Lanier says it takes 17 hours to prep just four minutes of footage.

This time-consuming, expensive process is necessary to protect the privacy of innocent bystanders, victims and children. And solutions, so far, are imperfect: The Seattle Police Department shares footage on YouTube, but because the feeds are blurred and soundless, their utility is fairly low. Automated redaction software hasn’t been developed yet, and until it arrives, police agencies may decide that privacy outweighs transparency.

5. Cameras will save lives.

That’s the whole point, right? As Sen. Scott says, if a picture’s worth a thousand words, then “a video is worth a thousand pictures and untold lives.” It’d be nice if that were true, but the jury’s still out. Early research with the Rialto, Calif., police department found that camera use is associated with lower rates of both police use of force and citizen complaints, suggesting that cameras have a “civilizing effect” on officers and citizens alike; that’s a good thing. But it’ll take more time, more research and — unfortunately — more trial and error to definitively say whether body cameras have a serious impact on the number of officer-involved deaths.

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