AS MORE AND MORE POLICE DEPARTMENTS adopt policies to have officers wear body cameras to record interactions with the public, the research evidence continues to build on the effects of the technology — and it’s not yielding the sort of findings many had expected.

The latest report, a review of 70 studies conducted by researchers at George Mason University, says there is mixed evidence of the benefit of cameras in reducing officer use of force, one of the main impacts many had expected. “There is an incongruence between people’s expectations of cameras, police expectations of cameras, and what they think they’re being used for,” Cynthia Lum, a co-author of the report tells Governing magazine.  

CommonWealth reported three years that evidence of the benefits of body cameras was far from conclusive. Underscoring how complicated the issue is, the story reported that there have been studies suggesting police use of body cameras may increase the likelihood of an officer being assaulted — perhaps because the cameras further provoke someone the officer is already having a confrontation with. While some studies have shown a decrease in officer use of force with civilians when wearing cameras, other studies have pointed to the opposite finding — showing a greater likelihood of police using force when wearing cameras.

Indeed, a study of all officer-involved fatal shootings in the US in 2015 found that police who were wearing cameras were slightly more likely to kill a civilian than those not wearing them. The authors speculate that knowledge that there will be video evidence could make an officer more likely to use deadly force in a case where he or she believes it’s justified but might otherwise have exercised restraint because of concern over the results of a follow-up inquest without such evidence.

Earlier this month, Springfield police supervisors reached a tentative agreement with the city on a new contract that includes use of body cameras. Springfield’s patrol officers’ union agreed last year to a new contract that calls for use of cameras by members.

Meanwhile, full deployment of cameras among Boston police officers, which a citizen group from the city’s black community has been pushing for several years, is on its way. A little over a year ago, researchers released the results from the pilot study of body cameras with Boston police. The findings pointed to a small benefit in terms of a reduction in citizen complaints about police conduct, while there was no apparent effect of cameras on police use of force against civilians.

Clearly, there are cases where camera evidence can serve as a check on possible police misconduct. Though the case doesn’t involve body-worn cameras, charges filed recently against three MBTA officers related to the beating of a homeless man at a Red Line station largely hinge on the availability of surveillance video from the station. As this CommonWealth look at the proliferation of surveillance video reported, T stations and buses are probably the most intensively surveilled public spaces in Greater Boston when it comes to video recording.

The new George Mason University review, however, said body camera recordings are being used far more often as part of the prosecution of cases against people police have arrested than to support misconduct charges against officers.

As Alex Sutherland, a researcher from RAND Corporation told CommonWealth three years ago about the findings from body camera studies, “the results aren’t as clear-cut as people might have assumed.”