Quick story: many years ago, my roommate and I were both selling LSD. A "friend" who was not a friend set us up to be robbed at gunpoint for the product and money. When a fight broke out and cops got involved (I am not ashamed of bolting out the door and running for help), we were taken to the hospital to be treated (we'd been pistol-whipped) but also interrogated. Standard good-cop / bad-cop tactics where they said they knew we were selling weed because my roommate had already confessed.
Well, the cops weren't terribly bright and accidentally allowed us to be seated next to each other at the hospital check-in area. We whispered back and forth that cops told both of us that the other ratted for weed. We concluded they had no knowledge of the LSD and agreed to both keep our mouths shut. The dope cops tossing our apartment overlooked a sheet of acid when it fell on the floor and we got away without charges.