Police Officers in the United States receive Qualified Immunity from Prosecution to protect them in court from the consequences of some of their actions. Oftentimes, especially if the citizens aren't white, officer behavior is so bad as to not warrant this immunity.
Make Qualified Immunity Contingent on that officer's body camera or dash camera footage being made available to the defense (and not just the prosecution). Privacy will be maintained but officers will (hopefully) think twice about supporting their fellows in illegal killings and other crimes (which they don't do now sufficiently).