Re: What bothers me most is this one
The expression is 'a few bad apples _ruins the whole barrel_'.
Police worldwide mostly share two traits: they're lazy and stupid. Not every single one, of course - some are driven, hardworking, evil powermad bastards.
Expecting police to do work they're not absolutely forced to do is unrealistic. Expecting them to do it when it'll affect their coffee-cooler mates who they 'know' are innocent is exponentially more so.