Who's Accountable for Police Killings?

In New York, the medical examiner called a videoed killing "homicide" by chokehold, but the grand jury did not return an indictment. In Ferguson, there was no video, and testimony conflicted, but there's been outrage nationwide because there was no indictment and no public trial.  Now in Cleveland, there are troubling new revelations about the white policeman who killed a 12-year old black boy playing with a toy gun in a public park.  President Obama wants to outfit cops with body cameras.  Will that help restore lost confidence in the justice system?