Body cameras were supposed to help improve policing. They aren’t living up to the hype.

A new study finds that research on the effectiveness of police body cameras has been very mixed.

When discussing ways to address the problem of police violence against black men and women, police body cameras — which are meant to increase accountability and help rebuild community trust — are often touted as a key part of the solution.

But a new study suggests that camera programs alone may not be as impactful as their proponents initially hoped.

The study, conducted by researchers from the Center for Evidence-Based Crime Policy at George Mason University and published Monday in the journal Criminology & Public Policy, is one of the largest reviews of academic research on body cameras to date.

And its findings are eye-opening: Researchers found that while body cameras are widely seen as a means of changing officer behavior for the better, in many departments the cameras have not had a consistent or significant effect on officer behavior or citizen opinion of police.

The study is the latest to note that body cameras, while potentially a very valuable tool in some contexts, should not be expected to single-handedly improve police accountability. Instead, the research suggests that body cameras are only as successful as the departments they are implemented in.

In other words, departments that want to see true improvements in officer-community relations must treat cameras as one step in a broader series of reforms supporting accountability and transparency.

“Expectations and concerns surrounding body-worn cameras among police leaders and citizens have not yet been realized by and large in the ways anticipated by each,” Cynthia Lum, a George Mason professor and one of the authors of the report, said in a statement. “It’s likely that body-worn cameras alone will not be an easy panacea for improving police performance, accountability, and relationships with citizens.”

Body cameras have been praised as an important tool for police accountability. Research on their effectiveness has been mixed.

In recent years, the use of body cameras has seen wide support. A May 2015 YouGov poll found that 88 percent of Americans polled supported the idea of police officers wearing body cameras.

That support, coupled with directives from the Obama administration and federal grant programs from the Department of Justice, further encouraged police departments to announce pilot programs. By 2016, surveys of police agencies found that some 95 percent of departments in major cities had either already launched body camera programs or planned to do so in the future.

The George Mason researchers, however, note that much of this support came while research on body cameras was still in its infancy, meaning that the rush to adopt body cameras came well before there was a significant amount of evidence showing that cameras were actually effective.

In the years since, two aspects of these programs in particular — the impacts of body cameras on officer behavior and officer perception of body camera programs — have received the bulk of academic research attention, the researchers note.

But the data has not been conclusive. Some of the studies the researchers looked at found that police wearing cameras receive fewer complaints, potentially suggesting that the cameras were changing officer behavior in a way that reduced negative interactions, while others found that the cameras had no effect on the number of police complaints.

The researchers also point out that even when studies did find a decrease in public complaints, it’s “unclear” whether that was a result of actual “improvements in officers’ behavior or their interactions with citizens,” or whether it merely reflected a change in citizens’ reporting behavior.

This point ties in with the second area body camera research has focused on: officer perception of body cameras. Interestingly, the report notes that while some studies found that police continued to dislike the cameras well after they were adopted (citing concerns about increased workloads and fears that camera programs would fuel a drawback in police activity), other studies found that officer opinion of camera programs actually increased the longer a camera program was active.

The researchers suggest that could be because officers see the cameras as a tool to hold the public accountable, instead of the other way around, as they were originally intended. For instance, one study included in the review found that 93 percent of prosecutors’ offices it examined used body camera footage to help prosecute civilians.

The research suggests that body cameras can be helpful — but initial statements on their effectiveness were likely overblown

Overall, the available research suggests that body cameras haven’t revolutionized accountability in policing or led to radical improvements in public opinion for the departments that have adopted them.

And while that might hamper some opinions on the significance of cameras, the Mason researchers also note that some of the biggest criticisms of body cameras — that they would fuel a reduction in policing activity or would lead to reduced officer motivation — also haven’t come to pass.

Still, the report does suggest the belief that body cameras will significantly alter police misconduct might be misplaced. Instead, in some departments, cameras “might exacerbate an already challenged relationship between citizens and the police, especially if citizens expect cameras to be used to increase police accountability and transparency, but officers primarily use them to increase the accountability of citizens,” the researchers write.

While some departments have recently announced that they would end or back away from launching camera programs due to high costs, the rapid spread of body cameras suggests that many departments will continue to use the technology. But there are still plenty of issues about how the cameras are used, particularly when it comes to who is able to access body camera footage, with civilians often being barred from viewing incidents of police misconduct.

It means that continued examinations of exactly what effects camera programs are having, and how their success or failure is influenced by other behaviors or procedures in a given police department, will be critical.

“To maximize the positive impacts of body-worn cameras, we suggest more attention to the ways and contexts — organizational and community — in which the devices are most beneficial or harmful,” Christopher S. Koper, a Mason professor and report co-author, explained in a statement.

“Attention should also be paid to how the cameras can be used in police training, management, and internal investigations to improve police performance, accountability, and legitimacy in the community,” he added.