If a police officer suspects you are in some way involved in illegal activity, they have the authority to stop you, whether you're walking, driving, biking, boating, or engaged in some other activity.âDuring a stop, you are not under arrest, but you are not free to leave," explains Tod Spodek, managing partner of the Spodek Law Group.âWhen an officer stops your car, the officer must have a reasonable suspicion that someone in the car committed a crime, or probable cause to believe the driver committed a traffic violation."