The only solution is to incentivize good behavior, not bad ones. Any time a police officer is caught doing something wrong, the money should be taken out of the local police pension fund. If one cop is bad, then ALL COPS SUFFER. This is the right incentive system, so that bad cops get weeded out.
First offence, depending on the severity, gets nothing. Second and subsequent get exponentially worse cuts to the pension fund. Good cops will weed out bad cops pretty quickly if they realize all their efforts are being lost because of bad behavior.