We're always checking our rearview mirror to see if a police car is anywhere close behind us, as we speed along on the highway. Just because you don't see a cop car in the mirror, doesn't mean they aren't on your tail.
Some people freak out if they are being pulled over by an unmarked police car and are unsure if the person driving is an actual police officer. I mean, for most of us being pulled over by a police car is a nerve-racking experience, so imagine seeing those lights on a non-cop car? Usually these unmarked cars are used for certain patrols and for traffic stops, so they still might look like police cars. They should have the same dash, deck, grille emergency lights and siren that we have come to expect. While some drivers might want to test them by continuing to drive, please don't. Just pull over and get it over with as soon as possible. The odds of it being an imposter are pretty low and you are only making things more difficult for yourself.
One important factor to remember is that in some states it is illegal for an officer to take any type of enforcement action for a traffic offense, while driving in a plain car and also in plain clothes. So if an unmarked car pulls you over, the officer should be in their uniform.
Always remember you have the right to fight any traffic violation. Finding the right defense attorney to contest a ticket may keep points off your license and save money on your auto insurance.