Ive heard of this before....
Speed by, lights come on, cop behind you.. radio in for backup. Backup arrives, officer gets out and holds the shotgun to your back window while the other officer comes to your window, pistol drawn yelling at you to get out of the car rite now.
If they cant see in, and your doing something bad, your asking for a world of hurt That story wasnt made up, it actually happened to my boss last summer, and he drives and old arse econo BMW.
Just be safe dude