We just got stopped by Tennessee K9 corp.
Yep, driving along at the speed limit we passed an officer's SUV. Not long afterwards, said SUV is travelling along side of us in the left hand lane. So, we do exactly what you would do: slow down. He slows down. We slow down. We get wigged but keep driving. That's when he pulls behind us ("Finally!") and puts on the lights ("F*ck!").
He comes to my side of the car -- the passenger side -- does the whole "license and registration" bit, and asked Seth to walk with him behind the vehicle. I sit and fret and try to read as much body language as posslible through the rearview mirrors. The officer doesn't shoot him and eventually walks back to me. I give him my ID and he asks me who Seth is, where we're going, etc. It's a corraboration thing, and evidentially my answers matched Seth because I too did not get shot.
Seth comes back to the car, turns the key in the ignition -- which is not so great because the car's running already and doesn't need to be started -- and we're back on our anxiety-filled way. No ticket.
Turns out that slowing down when a police officer stares at your car from the lane next to you is the kind of thing that drug runners do. Hence the momentary detection. To Seth's eternal credit, he didn't lose his temper.
Indignant comments: "Just another example of the militarization of the police force." "Yeah. 'We're just trying to keep you safe from the bad guys.' Just what Stalin said to his people."