The push for police departments to adopt body cameras is in full swing now, with Baltimore just announcing they’ve picked a supplier, the District is launching them this summer, and numerous other departments making plans to outfit officers with them.

Just this week, Taser International, the company best known for making, well, Tasers, announced a big boost in profits largely due to its sale of body cameras and the software used to store that video.

But what research has been done on the overall effect of police body cameras? Do they change an officer’s behavior? Do people on camera behave better? Do court cases become easier to resolve? How does a department save all that data, and for how long?

Answer: We don’t really know. Any of that.

The folks at George Mason University’s Center for Evidence-Based Crime Policy have launched a four-part research project into what is known and what needs to be known about body cameras, and their first part was looking at the existing research. “We discovered significant gaps,” wrote Cynthia Lum and Christopher S. Koper of Mason, “in our knowledge about their uses, as well as their intended and unintended consequences in both policing and court processes.”

In an interview, Lum pointed out that local governments are rushing to buy body cameras for their police forces nationwide without much study. “Often there are high expectations for technology,” Lum said. For body cameras, “citizens think it’s going to increase accountability.The police expectation is it will protect them from frivolous complaints. Those are two different visions of the role of technology in the police-citizen relationship. But accountability is a product of leadership, policies and practices, up to the chief and including line supervisors. That’s a good deal of infrastructure which body-worn cameras may only be a part of.”

Lum and Koper found only seven existing studies on body cameras in the U.S., though many more are underway. Of those completed, the review found that officers may not necessarily have negative attitudes toward the cameras, and that they may reduce or speed resolution of complaints against officers. But whether the cameras create increased accountability, improved behavior or reduce the use of force is not clear.

Similarly, more research is needed on whether the cameras cause officers to make more proactive stops and whether they impact the officers’ decisions to write tickets or make arrests, the Mason review found. Also unexplored is whether cameras will affect citizens’ willingness to call the police, cooperate as victims or witnesses, or simply comply with officers’ commands. The use of body cameras to facilitate police investigations of officer-involved incidents and also to improve training and policy have not been studied, the review found.

“I would be very concerned if body-worn cameras had an impact on people reporting to police,” Lum said. “Specifically vulnerable communities like victims of domestic violence, the elderly, minorities and immigrants. The privacy of reporting will matter to them. And let’s say it does cause that. Police will have to step up with some strategy to mitigate that.”

There also has not been much study of how the cameras impact the court system: whether they cause more plea bargains to occur, and whether their footage affects jurors’ decision-making. A survey of in-car police camera footage found that 58 percent of prosecutors reported a reduction in time spent in court because of the availability of video evidence, but many also spent more time preparing for cases. Whether the same will be true for body camera footage hasn’t been tested.

Lum said one of the surveys in progress involves prosecutors, asking them the impact body cameras will have. “Will it help with convictions, or hurt?” Lum asked. “Now, will people believe a witness without body-worn camera footage? These are issues that people didn’t think about when they jumped to body-worn cameras. So we have to play catch-up and we have to do it quickly.”

More details and lists of existing and planned research can be found in the review here.