If Dean got arrested, all of his stuff would get confiscated. Sam would have to freeze up and pretend to be an action figure, hoping that the person who grabbed him out of Dean’s pocket didn’t tighten their hand just a little too much and break anything. He’d have to hide that he breathes, and blinks, and do his best not to react at their forceful handling of his older brother.

Sam would be placed with Dean’s possessions in evidence bags, leaving him to have to cut himself an airhole to breathe from until he was left alone. Once no one was around, he’d cut himself out, find a way out of lockup, and get back to Dean. He could pick the lock on Dean’s cuffs and get them both out of there.