Well, I do not know how many "several" is, so I'll give you the one I am most familiar with: the John Burge Case in Chicago.
Although a federal probe concluded John Burge and several of his officers routinely tortured suspects to extract confessions, neither Burge nor any of his officers were ever prosecuted. Burge was forced to resign in 1993; however, he got a full pension and is still having his legal bills paid by the City of Chicago--to the tune of $8 million so far.
Think about it. Burge and his guys spent 20 years dragging suspects into a basement, smashing their heads with phone books, suffocating them with typewriter covers, shocking them with cattle prods, chaining them to hot radiators and running electric currents through their genitals. If you, me, or any civilian did such a thing, do you think we'd be collecting a pension and living free in Florida?
And are you really shocked that cops find it easier to get away with bad behavior than the general public? You shouldn't be. In any case, the evidence is everywhere: do a google search on police misconduct if you want more examples.