• Check if the police officer is in a marked police vehicle.
• See if the officer is in uniform. If the officer is not in uniform, request a uniformed officer.
• Remember, that if you really doubt the identity of someone trying to pull you over, you should proceed to a well-let, busy place such as a gas station, fast food place, convenience store, or police station. While doing so, turn on your four way flashers to notify the officer that you are aware he or she is trying to pull you over.
• Check if they have a badge.
• Ask for identification. Police carry identification clearly identifying them and their agency.
• Call 911 if you believe it’s a fake.

An unmarked police car can stop vehicles, but it must contain a constable who MUST be in uniform in order to carry out the stop.
If a car flashing for you to pull over or stop is unmarked, unless you are 100% certain it is the police, DO NOT STOP. Drive steadily to the nearest public place (for example a petrol station where they are open till late, a police station or somewhere there are a lot of people) and then stop.
If you are in a relatively deserted area, as a last resort, consider looking for a house that is obviously occupied and pull into the driveway. (You can always apologise to the householder afterwards.)
Try and signal that you have acknowledged the request to stop and indicate the action you are taking (put your flashers on or signal by pointing from the driver's window etc.). Don't drive off at great speed making the police think you are trying to get away.
Keep the doors locked until you are happy it is the police. Have your mobile at hand just in case. You can ask to see a warrant card, which should carry a name and photograph, through the closed window.