They don't mention what I think is the biggest benefit of body cameras - deterring bad behavior (by police and civilians).

When the Orlando, FL police department did a 12-month trial with body cameras:

In the 12 months from March 2014 through February 2015, use-of-force incidents — also known as “response to resistance” incidents — dropped 53 percent among officers with the cameras. Civilian complaints against those officers also saw a 65 percent decline. (http://www.huffingtonpost.com/entry/police-body-camera-study...)