A new study says body cameras have almost no effect on officer behavior.

And there is no significant difference in citizen complaints about camera-wearing officers versus those without cameras, the study says.

“Evidence of their effectiveness is limited,” researchers David Yokum, Anita Ravishankar and Alexander Coppock said about the cameras, in their report, titled, “Evaluating the Effects of Police Body-Worn Cameras.”

The study tracked more than 2,000 Washington, D.C., police officers – half with cameras, half without – for 18 months. The research team tallied their use-of-force situations, civilian complaints against them, etc., and examined whether cameras affected the results. If found that every measure showed the differences to be insignificant.

Police departments investing in body cameras “should not expect dramatic reductions in the use-of-force complaints, or other large-scale shifts in police behavior solely from the deployment of this technology,” study director Yokum, of The Lab @DC, told the Washington Post.