Illinois law requires you to take a breath, blood, or urine test if you are arrested for a DUI. Illinois’s “implied consent” law says that if you are lawfully arrested by an officer who has probable cause to believe that you have been driving under the influence, then you consent to taking a chemical test of your blood, breath, or urine for the purpose of determining your blood alcohol content (BAC). You do not have the right to speak to an attorney before you are tested, and the test must be given as soon as possible from the time when you were last driving. Although the arresting officer gets to choose which test you take, you have the option to get additional tests afterward taken by a medical professional of your choice.
You could be arrested for a DUI even if you were not driving. If you have actual, physical control of the vehicle while under the influence, then that can be enough for an officer to arrest you. Whether you have actual, physical control of a vehicle depends on where you are sitting, if you have the key, and if you have the ability to start and move the vehicle. In one case, an Illinois court decided that a person had actual, physical control of his car even though he had not driven it to the place where a police officer found him asleep. This person was lying across the front seat of his car with his head on the passenger side. He had the motor running to keep the heater on. Although this person did not intend to move the car, the combination of his position in it, the running motor, and evidence of his intoxication was enough for the court to uphold his DUI conviction. (This case is City of Naperville v. Watson, 677 NE 2d 955(1997).)
Additionally, Illinois law says that you consent to taking a preliminary breath test, even if you have not been arrested. This works like a field sobriety test. The officer will use the results to establish probable cause that you were driving under the influence. You do not have to take this preliminary test. Refusing it, however, probably won’t work in your favor if the officer has some other reason to think you had been drinking. Based on that other reason, the officer could still arrest you and then you will be required to take a test under the law described above.
You can read Illinois’s implied consent law in Illinois Statute 625-5/11-501.1.