Illinois Laws for Unmarked Police Cars

In the state of Illinois, police officers sometimes use unmarked police cars to monitor driver behavior, like speed. Under state law, an unmarked police vehicle is defined as one that does not have distinctive identifiable markings, but may have portable emergency warning lights. An officer may not use an unmarked police car to initiate a pursuit without a supervisor’s authorization. The exception is if the suspect’s continued freedom poses an imminent threat to life or great bodily harm.

It is helpful to review how unmarked police vehicles differ from semi-marked and marked police vehicles. A semi-marked police vehicle is one that is not identifiably marked by a distinctive color scheme. A semi-marked police vehicle may have red and/or blue lights that are mounted within the vehicle and be equipped with a siren.

A semi-marked police vehicle may have a partial police marking. A marked police vehicle is one that is identifiable by its color scheme, red and/or blue lights permanently mounted on or within the vehicle, and equipped with a siren. A marked police vehicle has a departmental seal and/or police or sheriff lettering.

Typically, a municipally owned vehicle operated by or for any police department will have a license plate with the designation “municipal police.” These license plates are numbered and distributed as prescribed by the Illinois Secretary of State. It may be that an unmarked police vehicle will not have such a designation on its license plate.

When two units from a law enforcement agency are in pursuit of a suspect, no other vehicles may join the pursuit. The exception is if a supervisor coordinates the pursuit. A vehicle pursuit typically should be conducted only with emergency lights and sirens. This means a marked police car typically has the primary authority to direct a pursuit.

When a driver of a motor vehicle flees after a stop has been initiated by a K-9 unit or a supervisor driving an unmarked vehicle, the K-9 unit or supervisor may participate in the pursuit. The goal is to have a supervisor or K-9 unit withdraw to a posture of support only. A law enforcement officer will attempt to safely have a marked police vehicle assume the pursuit.

Illinois state police or other types of law enforcement officers engaging in pursuits or traffic stops may use unmarked patrol cars. This can result in the driver who is being pursued being unaware that the officers following them are law enforcement officers with the power to make an arrest. When a person acts to knowingly detain another without legal authority, a state prosecutor may charge them with unlawful restraint. Unlawful restraint is a Class 4 felony punishable by one to three years incarceration and a fine up to $25,000.

A law enforcement officer has the authority to arrest a person when they have a warrant commanding that such person be arrested, they have reasonable grounds to believe that a warrant for the person’s arrest has been issued in Illinois or another jurisdiction, or they have reasonable grounds to believe that the person is committing or has committed an offense. There are situations in which a law enforcement officer in an unmarked police vehicle may not have a legal basis to arrest a driver. A driver who suffered an economic or physical injury because of such an interaction should consider speaking to a civil rights attorney.

The motorist may have a valid personal injury claim for malicious prosecution or false imprisonment. The statute of limitations for such a claim is two years from the date of the incident or arrest that led to the injury. Malicious prosecution in such cases could involve a state prosecutor initiating a criminal case against a defendant, the driver, without proper, reasonable or probable cause. False imprisonment here would involve unlawfully restraining or imprisoning the defendant-driver and illegally arresting them.