Body cams won't put an end to officer mistakes. Bad cops, good cops, it doesn't matter. If they are human cops, they are prone to making mistakes.
Cameras won't stop them from making bad mistakes but they aim to bring about accountability and thinking more carefully about your actions and they also are another set of eyes to help tell the story that may help bring about justice for the victim of police brutality but it also may help prove the cop wasn't guilty of any wrongdoing. The footage could also be used to improve training. Even if excessive use of force is used and no actions are brought against the officer(s), at least the victim may be cleared of their charges.
The big problem still lies with departments protecting their own when a mistake is made and not releasing footage. Or having footage go missing / get destroyed. Or having cameras turned off. We see this time and time again.
It will also not bring about justice in corrupt police departments like the Miami Beach police department, in corrupt cities with corrupt courts and corrupt police unions where all the video evidence in the world of an officer beating the day lights out of someone will not result in their termination.
Cameras will help but they won't solve the problem. That, I believe, will take some other steps.
This recent video demonstrates why I believe cameras alone will not solve the problems that exist.
https://www.youtube.com/watch?v=yluvnOjR60Y