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New studies on body-worn cameras deliver some surprises

In court, whether BWC video captures a complete or just a partial recording of a force event has “a profound impact” on an accused officer’s fate


One researcher recommends every patrol officer on a department is equipped with body cameras.

AP Photo/Ross D. Franklin

By Chuck Remsberg, Editor-in-Chief, The Calibre Report®

For the first time, a recent study reports “highly anticipated evidence” about how body-worn cameras (BWCs) are affecting federal litigation that alleges the use of excessive force by law enforcement officers.

A second recent study reveals how these increasingly prolific devices influence violator satisfaction and impressions of police “legitimacy” on traffic stops.

Some results from the two studies are surprising.

  • In court, whether BWC video captures a complete or just a partial recording of a force event has “a profound impact” on an accused officer’s fate. Footage that’s complete tends strongly to favor exoneration in a case, while a partial recording usually proves worse for defendant officers than no BWC video at all.
  • On traffic stops, researchers found that the same officer tends to leave significantly different impressions on violators, depending on whether the officer is equipped with a BWC. When the officer is wearing a camera, motorists are more likely to feel they are treated respectfully, fairly, and safely when being ticketed, notably improving “the perceived overall quality of police-public interaction.”

The judicial study was conducted by Prof. Mitch Zamoff, a former assistant US attorney in Philadelphia who now directs the litigation program at the University of Minnesota law school. His report, “Assessing the Impact of Police Body Camera Evidence on the Litigation of Excessive Force Cases,” appears in the Georgia Law Review and can be accessed free of charge here.

The traffic stop study was completed by an international team headed by Dr. Barak Ariel, an assistant professor and lecturer in experimental criminology at the University of Cambridge in England. His report, “Using Wearable Technology to Increase Police Legitimacy in Uruguay: The Case of Body-Worn Cameras,” appears in the American Bar Foundation’s journal Law & Social Inquiry and can be accessed without charge here.

“Moment of Truth”

When officers and agencies are sued under federal civil rights law for alleged use of excessive force, their attorneys almost invariably ask the court for a summary judgment in the defendants’ favor on grounds that the contested action was objectively reasonable or was protected under qualified immunity or both. If granted, summary judgment dismisses the case before trial. Zamoff calls these rulings “the moment of truth” in excessive-force litigation.

The first published summary judgment decision at the federal level involving a BWC occurred in 2014. Zamoff compiled all such decisions made in US federal circuits between then and the beginning of last year – 71 decisions total, believed to be the first such database of its kind. The jurists granted 45 defense summary judgment motions and denied 26, Zamoff computed.

He analyzed these decisions “to determine whether, from the court’s perspective, the bodycam video captured all of the pertinent events at issue in the lawsuit or whether it was only a partial recording.” In nearly one-third of the cases and for a variety of reasons, Zamoff determined, the video in question recorded “only a portion of the allegedly unconstitutional” police action.

He then compared the BWC-involved cases with 66 other summary judgment cases, drawn from the same judicial districts during the same time period and sharing similar scenario characteristics, but without BWCs involved.

Pivotal Factor

“The mere existence of any bodycam evidence does not increase…defendants’ likelihood of success on summary judgment in excessive force cases,” Zamoff discovered. What matters is how complete the video is. That’s what “moves the needle,” in his words.


  • Defendants won summary judgment almost 80% of the time when the judge was able to watch the entire incident on one or more BWC videos, Zamoff reports. This is nearly 30 percentage points higher than the rate of summary judgment rulings in favor of the police in cases where no video evidence was available. “The constant refrain from the courts [in the complete BWC] cases was that the video was so clear and incontrovertible that it eliminated any genuine issues…and permitted only one reasonable conclusion.” However, when just partial video was available, law enforcement lost summary judgment motions in nearly 70% of cases. “The rate of success for defendants in cases with complete bodycam videos is well over twice as high as in cases with only partial videos,” Zamoff writes.
  • Most surprising was this: You might think that partial video at least “would be better than no video at all in terms of figuring out what actually happened on the scene of an alleged incident involving excessive force,” Zamoff reasons. But in fact, partial video appears to reduce a defendant’s prospects for success, compared to offering no video evidence at all.

In the cases studied, defendants with partial videos succeeded in winning summary judgment 32% of the time, while those with no video prevailed 53% of the time. Far from helping the defense, in many cases “partial video only highlighted the existence of material issues of fact that…precluded the entry of summary judgment” and propelled the case to trial.

As Zamoff wryly notes, “All bodycam videos are not created equal.”

Looking Ahead

“As bodycam evidence becomes more and more commonplace,” Zamoff writes, “it is reasonable to predict that judges and juries will only become more dissatisfied with bodycam video that fails to tell the whole story.”

His recommendations:

  • “Expand the implementation” of BWC programs so that every patrol officer on a department is equipped with this technology;
  • “Minimize officer discretion concerning when to record” in order to maximize the probability of capturing complete videos;
  • “Impose meaningful consequences for the violation of mandatory recording rules.”

There’s a lot more meat from Zamoff’s study described in his Law Review article, including impressive findings that availability of BWC evidence significantly speeds up the judicial process. Well worth the read!

BWCs on Traffic Stops

Dr. Ariel’s study of BWCs on vehicle stops took place across five regions of the Uruguay National Traffic Force, encompassing both urban and rural environments in a country where crime levels tend to be higher than in the US.

During the 10-month study period, more than 7,800 drivers were ticketed in these areas by an unspecified number of officers wearing BWCs on some shifts and not on others. Researchers randomly selected a pool of 217 cited motorists – 122 of whom had been video-recorded while stopped – for telephone interviews about their perceptions of how the officers treated them.

Principal findings strongly underscore the benefits of BWCs, namely:

  • When the officers studied were wearing their BWCs, drivers they stopped were more likely to report having felt “listened to” regarding their story before the officer wrote the ticket…“treated with respect”…handled fairly, impartially, and with “sincere concern for their well-being”…and given “better” explanations of the officers’ decisions.
  • Drivers stopped when the officers were equipped with BWCs also “were more inclined to say they felt safe.” It appears, Ariel writes, that BWCs “strike out, or at least reduce,” citizen concerns about police “harassment, assault, or use of lethal force” that threatens their safety. With a camera present, “the driver and the officer(s) are not alone anymore, so misconduct or noncompliance is less probable.”
  • BWCs were significantly and “positively associated with overall satisfaction…justice…and effectiveness.”

Bottom line, says Ariel: “We found that BWCs can change perceptions of police behavior [and] lead to enhanced perceptions of [police] legitimacy…an increasingly important topic for policymakers.”

NEXT: How to buy body-worn cameras (eBook)

Our thanks to Atty. Michael Brave, Director of CEW Legal for Axon Enterprise Inc., and Dr. Mark Kroll, adjunct professor of biomedical engineering at the University of Minnesota, for their valuable assistance with this report.

This article is reprinted with permission from the Calibre Report. To subscribe, email Provided by Calibre Press.

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