[Eddy_Viscosity2]

The police have an enormous amount of power in the system. They can unilaterally decide to let people get away with something illegal, or arrest people for doing something fully legal because they felt like it. And even if prosecutors drop the charges in the latter case, being arrested, processed, and jailed until that happens is very much a punishment and an act of state violence in and of itself. The bad cops you mention, do exist and continue to exist because the police have so much power in the system that bad ones can't be fired for inexcusable behavior or even doing crimes themselves (exceptions exist, but are rare). They are as much as administrator of state power as the judges and prosecutors. I would even argue they are more so because of the directness of their actions.