As much as people like to complain about how corrupt the police are in how they cover up for each other, cases like this are decided by juries.
EDIT: If you haven't seen the video [0], you really should before commenting. This cop had no interest in actually apprehending Daniel Shaver. If he did, he would've done a more standard procedure like telling him to lay on his stomach with his hands either forward or on his back. There was no reason to tell him to walk forward on his knees, legs cross behind him, and arms up. You try doing that. Maintaining balance is a bit difficult. Now imagine trying to do that with the police pointing a gun at you.
This cop wanted to kill someone and create a story where he was the hero. For fuck's sake, the cop had "YOU'RE FUCKED" etched into the side of his gun!