I call that a "fishing trip". I worked nights at a restaurant as a kid. Late one night I'm pulling out of the parking lot. I see the two Eaton County cops across the street, and think nothing of it. I don't get fifty feet down Grand River Ave before they're on me. Both cars. They gave no excuse for pulling me over, ran my paperwork, performed an illegal search of my car for drugs (which I never had anything to do with.), and when they couldn't find anything to nail me on, they ripped my license plate off. (69 Camaro-spring loaded frame over gas cap) They wrote on the ticket that it was hanging upside down when they pulled me over!
It was a fix-it ticket, so after I popped the spring back in, I took it to Bath Police Chief, retired Detroit cop, Gene Reno. He was a great guy. He inspected my car and restored my faith in law enforcement when he said "You shoulda' asked them why they weren't out catching robbers. That's what they always said to me!"