I personally know a guy who almost went down for manslaughter which the police knew he couldn't have committed (he had been arrested for something minor on the other side of the country at the about same time the incident occurred). It took him about a year and a half to clear his name even though the police had documentation proving he couldn't have been there. They wanted him to go down for it that bad. They also beat him during questioning and tried to pressure him into a confession. He's a real quiet harmless guy too... So... There is NO WAY I'd trust the police.
Ok, fine, we'll never know the proportions. But you can get a confidential informant to say whatever you want for $100, and that can be enough for a search warrant. Then you don't call the shady CI at trial and work from the bust results instead.
No way to know how common it is, but I could see that method actually being good police work if they're putting away someone who needs to go away.
