DC law enforcement
At the Volokh Conspiracy, there's a post on law enforcement in the District of Columbia.
Frankly, I suspect DC police just get demoralized and jaded. Trying to enforce the law in a city where a sizeable percent of the population are convicted felons (I forget now the proportion, but it was pretty high), crime is constant, etc. must be pretty demoralizing after years.
To give you some idea of what I mean when I saw crime is constant: at one point they sent fire engines down the streets, shooting water under parked cars. Why? The coke dealers all hung out on those streets, and put their inventory under the cars. A customer would buy, and they would direct him to get it from under the car. That way they figured that, if busted, there would be no proof they possessed the coke. The volume of trade was so large that DC found it easier to just wash it all down the drain than to do what would be necessary to set them up.