Government, police, etc will always be corrupt. Always. People are people. The only defense is to give them just barely enough resources to do their job, with no excess or space for overreach. It's all about taxes - taxes are the only practical weapon the common voter has against government overreach, and the Constitution was written with this fundamental truth firmly in mind.
Of course, of all of Congress there are but a handful of congresscritters who actually are for less government spending, and usually the voter's choice is merely between which group of supporters the tax money will go to. That's a cultural problem in the US, and we can't begin to fix it until every call for lower taxes stops being dismissed with "you anarchist and probable racist, why do you want 0 government".
Fixing the problem starts with popular acceptance of the idea that one can say we're sending too much without being some extremist calling for the end of government. Less does not mean none - spread the word!