A major new study of body cameras and the Washington, DC Metropolitan Police Department (MPD) that was released last month found that the wearing of body cameras had no statistically significant effect on the number of use-of-force incidents and civilian complaints recorded.

How much of a reassessment of body cameras should this study prompt?

First of all, let’s note that this study was only focused on one aspect of body camera police oversight — their deterrent effect on officers inclined to engage in abusive or unprofessional behavior — which is only one possible benefit of the technology from a civil liberties perspective. It does not have implications for other potential benefits of body cameras such as resolution of factual disputes in critical incidents or other situations where complaints have been lodged against officers, better training, better overall police transparency and accountability, and increased trust between police departments and communities. It also does not have implications for the chief downsides of police body cameras: their potential to invade privacy, their risk of being reduced to just another tool for government mass surveillance, for example through their integration with face recognition capability, and their risk of becoming a propaganda tool if the police control what footage the public is allowed to see.

Still, the finding in this study seems surprising. A big reason we are concerned about surveillance is that it changes people’s behavior. There is a wealth of social science research showing that being monitored brings chilling effects and otherwise changes behavior. When it comes to police officers, who have been given the authority to use brutal, sometimes deadly force, we think such monitoring would be helpful if it improves their behavior. That is why we have been willing to accept body cameras if they are deployed with strong policies, despite the fact that they are government cameras with a very real potential to invade privacy.

So it seems surprising that police officers would not be affected by the monitoring (via bodycams) that they are being subjected to.

There are a number of possible explanations for the finding. They include:

MPD officers are already so good that there was no room for improvement via body cameras. As our colleague Monica Hopkins-Maxwell of the ACLU of DC observes in response to this study, that is hardly the case. However, there are far more troubled police departments in the U.S. than DC’s, and it stands to reason that the more ill-trained a police force, the more benefits bodycams will bring as a deterrent to bad officer behavior.

At the other end of the spectrum, officers might not change their behavior because they feel confident they won’t face any consequences for anything they are recorded doing. As Hopkins-Maxwell points out, experts have been “surprised” to find that the U.S. Attorney in D.C. hasn’t brought a single criminal charge against an MPD officer for using lethal force.

All officers have become aware of the ubiquity of cameras, including fixed CCTV cameras as well as bystander video, dashcam video, and the body cameras that some other officers around were wearing. Although some officers wore cameras and others didn’t, even the officers without cameras felt the same restraining effect as those wearing them. The authors of the study note that fully 70 percent of all calls for service examined in the study had at least one bodycam-wearing officer at the scene. If one officer had a bodycam and a control group officer didn’t, that one bodycam likely had an effect on both officers’ behavior. Officer awareness that the study was underway could have also contributed to a general atmosphere among officers of being under scrutiny, even among those without cameras.

It’s also possible that body cameras could have a strong deterrent effect in certain situations, but that those situations are too rare to show up in the statistics. Perhaps most police encounters happen in places where other people are or could be watching, and so officers’ general awareness that everyone carries a video camera restrains their behavior. But there could be very rare situations where a) an officer is alone with a civilian, b) is tempted to engage in abuse, and c) where only the presence of the body camera restrains that officer. If that were the case, the cameras would be providing a benefit that simply can’t be picked up in the statistical analysis.

In the end, we just don’t know the answers now. It is possible that further studies will shed more light. But at the end of the day, when it comes to assessing the costs and benefits of police body cameras, the most significant factor in the overall analysis remains whether cameras are deployed with a good policy framework to maximize their role as an oversight and community trust-building tool, and minimize their potential privacy invasiveness. Although frequently mischaracterized, we at the national ACLU have always been careful never to endorse body cameras in the sense of saying, “we think every police officer in America should be wearing one.” What we have consistently said is, “IF you as a community decide you want the oversight the cameras can bring despite their downsides for privacy, we think the cameras are okay if deployed with good policies in place.”

One final point: there is a real tendency for policymakers’ conventional wisdom to lurch from certitude to certitude based on the results of the latest study. For several years, conventional wisdom among body camera-watchers was that the technology would have dramatic effects, a view that derived largely from a single small study conducted in Rialto, California. That study (as we have been saying for several years) should not have been given the weight it was. This study is much larger and more rigorous, but neither should it be regarded as definitive. Even in physics, the findings of an experiment have to be repeated numerous times before it is generally accepted as true. When it comes to the incredibly complex and hard-to-study subject of techno-human systems such as body cameras, that should be true many times over.

In the final analysis, the police body camera debate should largely be focused on whether the benefits body cameras can bring for police transparency and accountability justify their costs, including their risks to privacy, and what laws and policies can be put in place to maximize the cameras’ benefits while minimizing their drawbacks. If body cameras help to reduce the occurrence of abuse, that would be a major benefit, but it would still be just one such benefit.