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(TNS) -- Police body cameras have become part of the uniform, a safety accessory along with the service revolver, pepper spray, riot baton and bullet-proof vest.

Video and audio footage from cameras clipped to officers' shirts is finding its way into courtrooms, used as evidence in criminal cases.

"We believe that it is now a 'best practice,' as well as good public policy, for all police to be equipped with body-cam technology," said Bob Miller, chief deputy prosecutor in Monroe County. "There is simply no better evidence of what occurs during a police-citizen encounter than video of the event."

In October 2014, a body camera clipped to BPD Officer William Abram's uniform recorded the sounds of gunshots from inside a dark residence where two women were being raped at gunpoint. The video shows two men escaping from a bedroom window and one turning and firing toward Abram, who shot back.

It documents just what happened and backed up the officer's account.

It's evidence. Strong evidence.

During a trial this month in Monroe Circuit Court in which a man was convicted of causing his 2-month-old daughter's death, deputy prosecutor David Gohn played for jurors a video and audio recording. It came from a Bloomington police officer's body camera that was on when the parents of the battered infant were told that despite efforts to revive her, Kenya Rose Smith-Barton had died.

"Mom, mom, mom ... oh my God, oh my God, oh my God," cried Robierre McNeil in the video. "No, no, no, my baby, my baby, my baby, my baby," wailed the child's mother, who was working a double shift at Burger King that Sunday a year ago when the baby was found unresponsive in a swing, suffering from several skull fractures.

The minutes-long segment was heart-wrenching.

Gohn suggested to the jury that McNeil's grief was not as genuine as the mother's. Jurors left to deliberate, with instructions on the law from the judge in their hands and the sounds of the anguished parents fresh in their minds.

McNeil was convicted of aggravated battery and neglect resulting in death and will be sentenced next month.

BPD Deputy Chief Joe Qualters said the department's body-worn camera policy requires that they be activated "to record all contacts with citizens while in the performance of official duties." He explained that the cameras are to stay activated "until the event is completed in order to ensure the integrity of the recording."

The policy does not extend to "any location where individuals have a reasonable expectation of privacy, such as a restroom or locker room," he wrote in an email response to questions.

Video from the cameras is downloaded at the end of each officer's shift and preserved on a server. Video not related to criminal cases is generally kept for six months, he said. Video involving arrests and circumstances where criminal charges are filed is passed along to the prosecutor's office and kept until the case is over.

What is pertinent and allowed as evidence for a trial is determined by rules of evidence and a judge's interpretation. Miller said body-cam evidence is available to both the prosecution and the defense.

"The rules governing its admissibility are no different than any other photographic or video exhibits," he said. "Clearly, it must be relevant to the issues before the court, and it must be properly maintained to avoid any risk of tampering."

He said that before such evidence can be used in an attorney's closing statement, as it was in McNeil's trial, it must first be admitted as an exhibit through a witness, most often the officer who was wearing it. "We believe that this kind of 'real time' evidence is helpful to jurors in many cases," Miller said. Sometimes, it helps determine a verdict.
©2017 the Herald-Times (Bloomington, Ind.) Distributed by Tribune Content Agency, LLC.

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Body Camera Footage Plays Vital Role as Evidence

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(TNS) -- Police body cameras have become part of the uniform, a safety accessory along with the service revolver, pepper spray, riot baton and bullet-proof vest. Video and audio footage from cameras clipped to officers' shirts is finding its way into courtrooms, used as evidence in criminal cases.

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Sign in with your credentials to access the EBSCOhost premium information resources provided by your subscribing institution.

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Police use of force has been heavily scrutinized for more than a year after fatal police encounters with unarmed black men in New York City, Ferguson, Mo., Baltimore and other parts of the U.S. The increased attention has renewed calls for law-enforcement officers to wear video cameras while on duty. Supporters say the devices are needed to provide transparency, build public trust and provide evidence against false complaints. But as more law-enforcement agencies begin using them, questions emerge as to when they should be turned on and off and how much footage should be made available to the public.

In May 2015, the U.S. Department of Justice announced that it was providing $20 million in grants to help local and tribal agencies purchase and learn to use body cameras. The grants are part of President Obama's plan to spend $75 million over three years to buy 50,000 "bod cams" for police organizations. Despite the national push, local law enforcement remains divided over the use of such technology, with some agencies blatantly resisting. Some of the agencies that have tried using them, however, are reporting decreased use of force and fewer complaints from residents. In San Diego, for example, a 2015 report based on preliminary statistics showed that body cameras helped reduce "personal body" force by officers by 46.5%.

A September 2015 study published in the Journal of Experimental Criminology used a controlled experiment with the Mesa Police Department in Arizona to determine how body cameras influence police-citizen interactions. For the report, entitled "The Impact of On-officer Video Cameras on Police-Citizen Contacts: Findings from a Controlled Experiment in Mesa, AZ," Justin Ready and Jacob Young of Arizona State University analyzed 3,698 field reports completed by 100 sworn patrol officers. The officers - half were assigned to wear body cameras - filled out the reports after having contact with members of the public between Nov. 1, 2012 and Oct. 1, 2013.

Key findings:

Officers who did not wear body cameras conducted more "stop-and-frisks" and made more arrests than officers who wore the video cameras. Officers who did not wear cameras performed 9.8% more stop-and-frisks and made 6.9% more arrests.

Officers assigned to wear cameras issued 23.1% more citations for ordinance violations than those who did not wear cameras.

Officers with body cameras initiated 13.5% more interactions with citizens than those who did not wear them.

Officers wearing cameras were 25.2% more likely to perceive the devices as being helpful during their interactions with the public.

The cameras did not have a significant impact on whether or not officers gave verbal warnings to citizens.

The study indicates that police officers were more cautious and risk averse when wearing body cameras. The authors suggest that the reason that camera-wearing officers may have made fewer arrests and conducted fewer stop-and-frisks was because they thought more carefully about criminal policy and procedures. With video evidence, there is the potential for greater scrutiny by supervisors or members of the public. The researchers note that a possible reason why officers with cameras wrote more citations was because they were worried they might be reprimanded for not issuing tickets when video evidence showed that a citizen had violated an ordinance or traffic law. Ready and Young's work offers insights that they think will be useful to law enforcement agencies as they decide whether to use this technology. "Police executives may support new technology that brings greater accountability and less civil liability, but line officers focus on how it may limit their use of discretion in the field," the authors state. "Empirical support showing that OVCs [On-officer Video Cameras] can help departments achieve their goals will reduce the time needed for this technology to gain legitimacy. Our findings represent a preliminary step in that direction."

Related research: A 2014 study from the U.S. Department of Justice, "Police Officer Body-Worn Cameras: Assessing the Evidence," offers a review of research on the costs and benefits of body cameras. A 2010 study conducted by some of the nation's leading criminal justice scholars, "A Multi-method Evaluation of Police Use of Force Outcomes: Final Report to the National Institute of Justice," provides an overall summary of police use-of-force issues. A 2014 report in the Annual Review of Law and Social Science, "The Law and Social Science of Stop and Frisk," surveys recent scholarship on the effectiveness of police stop-and-frisk tactics.
Keywords: police brutality, excessive force, body cameras, body cams, body-worn cameras, technology, policing, Eric Garner, Michael Brown, Tamir Rice, Freddie Gray, Freedom of Information, public records
Last updated: July 1, 2016
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Citation: Ready, Justin; Young, Jacob. "The Impact of On-officer Video Cameras on Police-citizen Contacts: Findings from a Controlled Experiment in Mesa, AZ." Journal of Experimental Criminology, June 2015. doi: 10.1007/s11292-015-9237-8.

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Do body cameras change how police interact with the public? - Journalist's Resource

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Police use of force has been heavily scrutinized for more than a year after fatal police encounters with unarmed black men in New York City, Ferguson, Mo., Baltimore and other parts of the U.S. The increased attention has renewed calls for law-enforcement officers to wear video cameras while on duty.

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In the United States, only a small fraction of the over 17,000 law enforcement agencies track officers' misconduct reports. The reason for this is unknown. If an officer is cleared of charges and honored for the actions, then any initial reports will not be part of the tracking mechanism.

A vast majority of Americans support the thin blue line. We all want good officers to succeed. Police officers risk death every single day. The sacrifices that law enforcement make on our behalf are often overlooked and underappreciated. Police brutality statistics should not exist, but they do because a small minority of officers abuse their privilege.

The other side of the story is all of the police officers who are injured in the line of duty. This is not referring to the fact that, in spite of the dangers of Covid-19, police officers have still gone to work and Covid-19 has now killed more police officers than all other causes combined (as of September 2020). It is referring to, for example, the over 317 police officers who were injured or killed in protests or targeted attacks...in the week of May 25, 2020 alone (Federalist, June 5, 2020).

Statistics About Police Brutality

1. Police officers are indicted in fewer than 1% of killings, but the indictment rate for civilians involved in a killing is 90%. (FiveThirtyEight)

2. On average, in the United States, a police officer takes the life of a citizen every 7 hours. (Fatal Encounters)

3. In 2015, there were 1,307 people who lost their lives at the hands of a police officer or law enforcement official. In 2016, that number was 1,152. Although lower, both years are still higher than the 1,149 people who were killed by police in 2014. (Fatal Encounters/Mapping Police Violence)

4. 52% of police officers report that it is not unusual for law enforcement officials to turn a blind eye to the improper conduct of other officers. (US Department of Justice)

5. 61% of police officers state that they do not always report serious abuse that has been directly observed by fellow officers. (US Department of Justice)

6. 43% of police officers agree with this sentiment: "Always following the rules is not compatible with the need to get their job done." (US Department of Justice)

7. 84% of police officers have stated in a recent survey that they have directly witnessed a fellow officer using more force than was necessary. (US Department of Justice)

8. Just 5% of the police departments in the United States contributed statistics to a 2001 report that was created to track police brutality on civilians. (US Department of Justice)

9. The estimated cost of police brutality incidents in the United States is $1.8 billion. (Cop Crisis)

10. 93.7% of the victims of police brutality that involve the discharge of a weapon are men. (The Guardian)

11. People who are African-American/Black are twice as likely to be killed by a police officer while being unarmed compared to a Caucasian/White individual. The reasons or circumstances of the deaths are not revealed. (The Guardian)

12. Native Americans are just as likely to be killed by law enforcement officials in the United States as African-Americans/Blacks from 1999-2013 data. (CDC)

13. 1 in 4 people who are killed by law enforcement officials in the United States is unarmed. The reasons or circumstances of the deaths are not revealed. (Mic)

14. Out of the 2.3 million people who are incarcerated in the United States right now, an estimated 1 million of them are African-Americans/Black. (NAACP)

15. The most common form of police misconduct in 2010 was excessive force. This is similar to the data that was collected in 2001 by the US Government. (Cato Institute/US Department of Justice)

16. The second most common form of police misconduct is sexual assault. (Cato Institute)

17. 1 out of every 3 people that are killed by police officers in any given year in the United States is African-American/Black. (Mapping Police Violence)

18. Where you live matters when it comes to police brutality. If you are an African-American/Black individual, then you are 7 times more likely to be killed by a police officer in Oklahoma than you are if you lived in Georgia. (Mapping Police Violence)

19. In 17% of the 100 largest cities in the United States, police officers killed African-American/Black men at a higher rate than the US murder rate of 2014. (Mapping Police Violence)

20. Although Chicago draws a lot of attention due to its total number of murders, including a threat from the Executive Office to "bring the Feds" in 2017, it ranks 25th in the 100 largest US cities for police officers killing African-American/Black men. (Mapping Police Violence)

21. 69% of the victims of police brutality in the United States who are African-American/Black were suspected of a non-violent crime and were unarmed. The reasons or circumstances of the deaths are not revealed. (Mapping Police Violence)

22. The levels of violent crime in US cities are not a factor in the likelihood of police brutality occurring. An individual is 15 times more likely to be the victim of police brutality in Orlando, FL compared to Buffalo, NY even though Orlando has a lower violent crime rate. (Mapping Police Violence)

23. 97% of the cases of police brutality that were tracked in 2015 did not result in any officer involved being charged with a crime. (Mapping Police Violence)

24. 27% of police killings in the United States from 2013-2016 were committed by police departments in the 100 largest cities in the country. (Mapping Police Violence)

25. African-American/Black people were 39% of the people killed in the 100 largest cities in the US, despite being only 21% of the population in these cities. (Mapping Police Violence)

26. Only 3 police departments in the largest 100 cities in the United States did not kill anyone from 2013-2016. Those cities are Buffalo, New York; Irvine, California; and Plano, Texas. (Mapping Police Violence)

27. African-American/Black and Hispanic police officers are more likely to fire their weapon than Caucasians/Whites, especially when confronting an African-American/Black suspect. (US Department of Justice)

28. African-American/Black police officers are 3.3 times more likely to fire a gun at a crime scene than other cops. (Ridgeway)

29. Police officers are 18.5 times more likely to be killed by an African-American/Black person than a police officer killing an unarmed African-American/Black person. The reasons or circumstances of the deaths are not revealed. (FBI)

30. 135 police officers were killed in the line of duty in 2016, which was the highest number of fatalities in the past 5 years. (Time)

31. The number of police officers who were killed in 2016 in ambush-style attacks: 21. (Time)

32. More than 900,000 law enforcements serve across the United States at any given time over the course of a year. (Time)

33. The average number of fatalities suffered by police officers in the United States over the past 10 years: 151. The average number of civilians killed by police officers over the past decade per year: 1,058. (Time)

34. 1930 was the deadliest year for police officers in the United States, with 307 officers killed in the line of duty. (Time)

35. Of the people that are killed by the police while not attacking, 39% of those people are African-American/Black individuals. (Vox)

36. 42% of African-American/Black individuals who were killed by police during their arrest were not attacking when they were killed and they were not killed with a rifle or a shotgun. (Vox)

37. The Dallas police department has implemented mandatory de-escalation techniques as part of their officer training. As a result of this effort, the police department experienced a 60% drop in the number of complaints against police from 2009-2014. It also resulted in a 30% drop in police assaults and a 40% drop in police shootings. (Dallas News)

38. Even though police body cameras have been being implemented across the United States, in New Orleans in 2014, 59% of the time the cameras were not on when police officers were in a use of force event. (The Nation)

39. 15 states are seeking to exempt body camera footage from Freedom of Information Act laws that exist. (The Nation)

40. In the first systematic study of police brutality in 1971, it was found that the overall rate of unwarranted force to be low: about 1% of all encounters with citizens. (ACLU)

41. In a 1982 Police Services Study funded by the Federal Government, 12,022 people were randomly interviewed in 3 metropolitan areas. 13.6% of those interviewed were found to have cause to complain about police services in the previous year, but only 30% of those who had cause to complain actually started a formal process. (ACLU)

42. 10% of police officers account for 33.2% of all use-of-force incidents. (Christopher Commission)

Blue lives matter. Black lives matter. All lives matter. There are police departments doing an exceptional job and should be commended. Police officers put their lives on the line every day to protect us. By following what they are doing right and fixing the reasons why things go wrong, the United States should be able to improve the system for all people.

Blog Post Author Credentials
Louise Gaille is the author of this post. She received her B.A. in Economics from the University of Washington. In addition to being a seasoned writer, Louise has almost a decade of experience in Banking and Finance. If you have any suggestions on how to make this post better, then go here to contact our team.

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In the United States, only a small fraction of the over 17,000 law enforcement agencies track officers' misconduct reports. The reason for this is unknown. If an officer is cleared of charges and honored for the actions, then any initial reports will not be part of the tracking mechanism.

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Evidence they don't work vs they do
Stats Below

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Equipping police with body cameras may be an effective way to improve the behavior of officers and the public with which they interact, a new study finds.

Last week, researchers at the University of South Florida released their report on a yearlong body-worn camera pilot program at the Orlando Police Department, in which they randomly selected 46 officers to wear the devices and compared them against 43 officers who did not.

In the 12 months from March 2014 through February 2015, use-of-force incidents -- also known as "response to resistance" incidents -- dropped 53 percent among officers with the cameras. Civilian complaints against those officers also saw a 65 percent decline.

The study also showed significant reductions in the number of civilian injuries by officers wearing body cameras, and of injuries to the officers themselves.

Officers who didn't wear body cameras in the study also used force fewer times over the year, though the drop-off was less substantial.

The study comes amid a nationwide effort to outfit more police forces with body cameras following high-profile police killings and instances of misconduct, which have spurred calls for improved transparency and accountability. Body cameras have emerged as a rare point of agreement between reform advocates and law enforcement officials, and in December, President Barack Obama announced a $75 million initiative to help departments cover the costs of expanding their programs.

Dr. Wesley G. Jennings, principal investigator for the study and associate chair in USF's Department of Criminology, said officers in Orlando were initially skeptical about the equipment, with some claiming that body cameras wouldn't change their willingness to use force during an arrest. The statistics appear to tell a different story, even though only one in four officers in the study agreed that wearing the devices had any impact on their behavior in the field.

Many officers reported that the equipment changed citizen behavior and helped to de-escalate confrontations between civilians and police. They also said body cameras improved evidence collection, and helped them more accurately recollect events and fill out reports. According to Jennings, most officers didn't feel burdened by the body cameras.

"The BWC officers overwhelmingly reported that the BWCs would not reduce their willingness to respond to calls, nor would it reduce their self-initiated subject contacts when a crime had been committed," Jennings said in a statement. "Most felt that the BWCs made them better officers."

After the conclusion of the study, two in three officers who wore the cameras said they'd want to continue wearing them in the future. A majority also said the agency should adopt body cameras for all front-line officers.

Orlando Police Chief John Mina supports this push, and he's getting help in the form of a roughly $500,000 federal grant for the equipment.

"BWCs will also improve accountability and transparency, protect our officers from false complaints, and provide valuable evidence for prosecutors," said Mina in a statement.

Other studies have pointed to similar drops in use of force and civilian complaints after the implementation of body cameras. In Rialto, California, a study of a yearlong program that concluded in 2013 showed a 59 percent reduction in use-of-force incidents by officers wearing cameras, along with an 87 percent drop in civilian complaints, compared to the previous year's totals.

While body cameras have shown promise in these areas, skeptics have been quick to point out that the effectiveness of the equipment will ultimately be determined by the policies that govern their use. In cities and states around the nation, for example, police departments and lawmakers are already working to limit public access to footage. Critics have also expressed concerns that certain guidelines will make it too easy for officers to tamper with cameras, use the video only for their own benefit or turn the devices into a tool for broader surveillance.

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Study Shows Less Violence, Fewer Complaints When Cops Wear Body Cameras

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Equipping police with body cameras may be an effective way to improve the behavior of officers and the public with which they interact, a new study finds. Last week, researchers at the University of South Florida released their report on a yearlong body-worn camera pilot program at the Orlando Police Department, in which they randomly selected 46 officers to wear the devices and compared them against 43 officers who did not.

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The Rialto study had a big impact in policing. Axon (formerly known as Taser International) has sold more than 300,000 police cameras worldwide and cites the Rialto study on its website. A federal district judge also cited the study in 2013 when she ordered the New York City Police Department to conduct a yearlong pilot program using body cameras. (Results are due out this spring.)

But the Rialto experiment featured just 54 officers, compared with over 2,000 in Washington. Officers in Washington captured five times as many hours of video. The larger sample size and the long-term way the cameras were assigned added to the reliability of the D.C. results.

"This is the most important empirical study on the impact of police body-worn cameras to date," said Harlan Yu from Upturn, a Washington, D.C., nonprofit consulting company that studies how technology affects social issues. It was not directly involved in the research. "The results call into question whether police departments should be adopting body-worn cameras, given their high cost."

The federal government has given police departments more than $40 million to invest in body cameras, and state and local authorities have spent many millions more. The devices vary in price, but the biggest expense is the data-storage cost. In Washington, M.P.D. officers collect about a thousand hours of footage a day. About 40 percent of it is deleted within 90 days, while the rest is to be kept for months, years or decades, depending on the statute of limitations for the charges connected to the footage.

The cameras also have a cost in terms of privacy violations. In a report on the policies governing police body cams in 50 major departments, Upturn and the Leadership Conference on Civil and Human Rights found that many cities have weak rules in place. Those rules can allow departments to refuse to share footage with civilians who want to file complaints, for example.

Some companies are exploring ways to integrate facial recognition software into police cameras, a level of surveillance that would disproportionately affect low-income minority communities, where the police tend to spend the most time.

"D.C. has relatively strong body-worn-camera procedures," Mr. Yu said. "In cities that have weaker policies, it's certainly possible that the cameras may be doing more harm than good." Like other advocacy groups, the American Civil Liberties Union has supported body cameras. But the study, says Monica Hopkins-Maxwell at the A.C.L.U. of D.C., "should give us pause."

For now, Washington officials say they intend to continue using cameras. But they admit to being surprised by the findings.

"I thought it would make a difference on police and civilian behavior - particularly for officers, and this is the exception, who might be more inclined to misbehave," said the M.P.D. chief, Peter Newsham.

Why didn't the cameras change behavior? After all, we know that other cameras do change behavior. Public closed-circuit TV cameras seem to lead to a moderate decrease in crime, particularly in parking garages. Traffic cameras significantly decrease speeding and fatal accidents.

Even the suggestion that someone is watching us tends to influence us: In 2011, researchers at Newcastle University in England posted pictures of a pair of male eyes and the caption, "Cycle Thieves: We Are Watching You." Bike thefts decreased by 62 percent in those locations - and not elsewhere.

One hypothesis is that officers got used to the cameras and became desensitized to them. But the researchers saw no difference in behavior during the initial phase, when the cameras were new. (The researchers also checked the data to make sure officers were turning their cameras on when they were supposed to, and found a very high level of compliance.) Another possibility is that officers without cameras were acting like officers with cameras, simply because they knew other officers had the devices.

An equally plausible explanation has to do with fear: In Washington, police officers are instructed to turn on their cameras whenever they answer a call or encounter the public in a law-enforcement context. The kinds of situations that might lead to civilian complaints or use-of-force incidents are high-stress encounters. When frightened, humans tend to act on automatic fear responses (or, in the case of good police officers in an ideal world, training).

"It's a lot to ask, psychologically speaking, to not only remember the camera is on but to moderate your behavior," said Mr. Yokum, the head of the Lab @ DC.

Finally, cameras may have had less impact in Washington, because the police department there has already had to confront excessive-force problems. After a devastating 1998 Washington Post series revealed that the city's police department had shot and killed more people per resident in the 1990s than any other police force in a large American city, the Department of Justice entered into a memorandum of agreement with D.C. to reform its policing.

"We went through a transformation with regard to use of force when Justice came in here," Chief Newsham said.

Cities that lack such accountability in their police culture may find cameras more effective, under this theory. (The Rialto Police Department had been reeling from a series of scandals when the Rialto study showed a large impact from cameras.)

Even if cameras do not reduce violent encounters, they can still offer other kinds of benefits: for training, or to hold a rogue officer accountable after the fact.

To Chief Newsham, the cameras' primary benefit is to improve relations with the community. "The transparency and trust that the community has, knowing your department is recording the interactions, I don't think you can undervalue that," he said. So far, it's hard to say for sure if cameras increase trust, but Chief Newsham said he'd like to find out more through additional studies like this one.

The nine-person research team pre-published its design online, so that there would be less temptation to rejigger the approach after the results were in (an emerging best practice in social science research).

"We like to be very anecdotal in policing - to compare this year to that year," said M.P.D. Commander Ralph Ennis, who oversaw the rollout of the cameras and worked closely with researchers. "This study is a whole other thing."
An updated version of this article, with more about the national implications of the Washington, D.C., study of police body cameras, can be found here.

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A Big Test of Police Body Cameras Defies Expectations

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The Rialto study had a big impact in policing. Axon (formerly known as Taser International) has sold more than 300,000 police cameras worldwide and cites the Rialto study on its website. A federal district judge also cited the study in 2013 when she ordered the New York City Police Department to conduct a yearlong pilot program using body cameras.

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Chief Peter Newsham of the Metropolitan Police Department in Washington said the results were surprising. "I thought it would have a difference on police and civilian behavior," he said. "Particularly for officers - and this is the exception - who might be more inclined to misbehave."

But Chief Newsham said the cameras had a number of benefits that could not be easily measured: more accurate investigations, better training and at least one case in which the footage exonerated an officer accused of shooting an unarmed suspect (who was indeed armed). Most important, he said, they bolstered the trust of the community.

"You have to be legitimate and trusted," he said. "You can't underestimate the value these cameras bring to that."

Behavior modification has never been the sole argument for body cameras. Their most important function may be to create an independent record of police shootings and other encounters with the public. But in some of those areas, too, videos have proved ambiguous: In the courtroom, for example, they have repeatedly failed to persuade juries.

Though body cameras are now in greater use, their purpose is often left undefined, raising thorny questions about surveillance, privacy and other issues. "Police departments have been rushing to body cameras without sufficiently deciding what the goal is," said Seth Stoughton, a former officer and a law professor at the University of South Carolina, who has studied the devices extensively. "When no one is sure what it is supposed to do, no one knows if it is working."

In the Washington study, which was conducted by David Yokum at the Lab @ DC, a team of scientists embedded in local government, and Anita Ravishankar of the Metropolitan Police Department, more than 1,000 police officers were randomly assigned cameras, and another 1,000 were not.

Each officer was tracked for seven months, with the researchers recording use-of-force incidents, civilian complaints, charging decisions by prosecutors, and other outcomes to see if the cameras changed behavior. On every metric, the effects were too small to be statistically significant.

"The results call into question whether police departments should even be adopting body-worn cameras, especially given their high cost," said Harlan Yu, from Upturn, a Washington nonprofit consulting company that studies how technology affects social issues. It was not directly involved in the research.

Mr. Yu said the cameras raised significant privacy issues, particularly in low-income, minority neighborhoods, and that vendors were beginning to experiment with incorporating facial recognition software. "As an evidentiary tool, they will likely get stronger over time," he said. "But the original purpose of cameras - transparency and accountability - could ultimately get swept under the rug."

Criminologists said there were several possible explanations for the cameras' apparent lack of impact. The Metropolitan Police Department has a reputation for being better-than-average in terms of both training and supervision, so whether officers wear cameras or not may have made little difference in their behavior.

The department has already had to confront excessive-force problems. After a Washington Post series in 1998 revealed that the city's officers had shot and killed more people per resident in the 1990s than any other police force in a large American city, the Department of Justice entered into a memorandum of agreement with the city to reform its policing.

"We went through a transformation with regard to use of force when Justice came in here," Chief Newsham said.

Under this theory, cities that have not had such reviews and calls for accountability may find that cameras have a greater effect.

Criminologists also suggested that the effect of the body cameras diminished over time, and that officers began to behave as they had before they started to wear the devices. Although if that were true the researchers would have found a greater gulf between those with and without cameras at the beginning of the study, which they did not. Or, the effects of the cameras may have spilled over to officers who did not wear them, just because they knew their colleagues did.

"This area of police practice is under-researched, so we really don't know a lot," said David A. Harris, a professor at the University of Pittsburgh School of Law who studies police accountability. "In this police department, cameras had a certain effect, but you cannot extend that to other police departments."

Until now, the most commonly cited study on police body cameras had suggested that they did indeed have a calming effect. That experiment took place in 2012, in Rialto, Calif., where officers were randomly assigned cameras based on their shifts. Over a period of one year, shifts that included cameras yielded half as many use-of-force incidents (including the use of a police baton, Taser or gun) as shifts without cameras did. The number of complaints filed by civilians against officers also declined - by 90 percent compared with the previous year.

The Rialto study had a big impact in policing. Axon (formerly known as Taser International) has sold more than 300,000 police cameras worldwide and cites the Rialto study on its website. A federal judge also cited the study in 2013 when she ordered the New York City Police Department to conduct a yearlong pilot program using body cameras. (The department has outfitted 927 officers with cameras and will compare their performance with officers without; results are due out this spring.)

But the Rialto experiment included just 54 officers, compared with over 2,000 in Washington.

In another new study that will be published in the November issue of the journal Policing, researchers led by Michael White of Arizona State University interviewed 249 people who had recent encounters with officers wearing cameras. Those who were aware of the cameras perceived the encounters as more "just" than those who were not.

Monica Hopkins-Maxwell, executive director of the American Civil Liberties Union of the District of Columbia, said cameras were "not a panacea" and that only more emphasis on initiatives like community policing, data collection and better training would help build good will.

"I don't think body cameras in any way, shape or form by themselves increase trust," she said. "The way you increase trust is through relationships and how communities are treated by police officers."

Professor Harris, of the University of Pittsburgh, said that the impact of body cameras will remain a disappointment to many people given the hype surrounding them once video footage of police behavior - good and bad - went viral on the internet.

"We were sold on the idea that these cameras were going to bring a brand-new accountability to policing, and that isn't entirely what has happened," he said.

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police brutality  misconduct and shootings

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Body Cameras Have Little Effect on Police Behavior, Study Says

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Chief Peter Newsham of the Metropolitan Police Department in Washington said the results were surprising. "I thought it would have a difference on police and civilian behavior," he said. "Particularly for officers - and this is the exception - who might be more inclined to misbehave."