This means there is a right way and a wrong way to do police work. The right way and the wrong way are defined by law. Failure to follow the simple job requirements of being a policeman can result in having the case thrown out. For instance planting evidence on a suspect is disallowed. All that is a mute point now.
As a suspect Mike Brown should have been arrested. He should have been provided a lawyer, he should have had a trial. This is what due process requires and due process is a constitutional requirement.
It is one thing for a policeman fighting for his life to kill a suspect, it is something quite different to shoot a suspect who has his hands over his head and is surrendering. What the policeman did when killing Mike was to remove Mikes civil liberties from him and in doing so I believe he committed a federal civil rights violation. Denying someone their civil rights is a very serious offense.