That experiment has actually been tried...
There is nothing worse than a corrupt police officer -- just look at the comment section under any taser video on YouTube. Unfortunately for the citizens of the country of Georgia, that was pretty much the only flavor their traffic cops came in. In 2004, things had gotten so bad that the newly elected President Mikheil Saakashvili made it his mission to stop the police from harassing his people.
Saakashvili didn't mess around, either. He fired all the heads of law enforcement and threatened that any traffic cop caught harassing civilians, taking bribes or generally behaving all uppity would be fired or arrested. The police force scoffed at the attempts of this puny "president" person and behaved exactly like they always had, confident that Saakashvili wouldn't touch them. So, the very next day after this announcement, when a whopping 15,000 cops were caught taking bribes, Saakashvili fired every single one of them.
Then, a couple of weeks later, another 15,000 police officers were caught participating in shenanigans. So he fired them, too. With 30,000 corrupt officers freshly in the unemployment line, Saakashvili had finally succeeded. The police department was finally clean! Huzzah! Only, there was one little problem. There were no traffic cops left...
Instead of indulging in a nationwide game of bumper cars, everything went just fine -- in fact, even better than normal. And we don't mean that the citizens held themselves together for a couple of days until new cops could be hired. They were without police for three freaking months. And it was fine.
Saakashvili's administration quickly realized this was because it had been the cops causing most of the trouble all along. A remnant from the Soviet era, they'd treated the roads as their personal piggy bank, administering their very own brand of expensive justice at will and causing mob-style chaos as they did. When they were taken out of the equation, not even a hint of disorder was left because they had been the disorder.
http://www.cracked.com/article_19489_5-terrible-ideas-that-solved-huge-global-problems.html
O.K. so we don't have that level of omerta among cops in our country. But I notice, for example, that in Omaha, Nebraska, large number of cops went on a rampage in a black neighborhood, beating civilians entering a house with no warrant, and seeking out cell phones to destroy the evidence.
Not all of them, of course, but not one of the "good cops" turned in the criminals. Unfortuately for the criminals, there was another camera in the house across the street that caught the whole thing.
And of course because of that video, the crooks were indicted instead of their intended victims. But apparently, not one of the police who stood by and later declined to turn in the crooked cops, were disciplined at all. The chief more or less concluded "that's what they do, and I can't do anything about it."