The Supreme Court has held that random vehicle stops are unreasonable seizures under the Fourth Amendment. Police officers are required to have probable cause in order to justify stopping a vehicle, or at the very least a reasonable suspicion that a driver is violating some law or traffic code, such as if you have been street racing. Thus, police cannot randomly stop vehicles simply to check a drivers licenses or even to get a better view of drivers and passengers unless there is a reason to suspect them of some kind of criminal activity afoot. If a police officer does make a random stop of a vehicle, any evidence found in the car or on the passengers can be suppressed.

What About Stops at Roadblocks?

According to the Supreme Court, random stops are an unconstrained exercise of discretion because they are random. Roadblocks, by contrast, where every motorist is stopped and questioned, are permissible since it is not random. In fact, it is not even required that every motorist is stopped as long as the decision on who is stopped is based on a neutral, predetermined system, such as every fifth car.  

However, there must be some public interest in having the roadblock. For example, sobriety checkpoints have been held constitutional, though several states have invalidated their use under state laws.

What Should Someone Do if They Have Been Stopped Randomly?

First of all, even if a driver suspects they have been stopped randomly, they should cooperate fully with police officers and follow normal guidelines for traffic stops. Next, they should ask why they were stopped. Remember that no one is required to answer questions without speaking to a lawyer, and the police cannot search a car during a stop without probable cause.

Do I Need a Lawyer?

If you have been arrested following a stop without reason or probable cause, you should contact a criminal defense lawyer immediately. A lawyer can advise you of your rights and defenses under the law and seek to have any evidence found in the course of the traffic stop suppressed. If need be, a lawyer can zealously represent you in court.