You can be charged in Illinois with Driving Under the Influence (DUI) even though the police may not actually observe you driving. This Chicago Sun-Times article describes a man who was charged with DUI despite the fact that at the time of the arrest, his car was pulled over and notwithstanding the fact he was rear-ended.
Blake, perhaps concerned that he was too impaired to be driving, parked his car on the shoulder. Although he failed to pull completely over, the fact remains that his vehicle was struck from behind and he was not driving at the time. However, Illinois DUI law provides that you are considered to be driving under the influence if you are in “actual physical control” of your vehicle while under the influence of alcohol.
Many DUI arrests begin when authorities find a driver asleep behind the wheel, or asleep in the back seat of the car, or even outside of the car. As long as the state can prove to a jury that the driver either had been driving or was capable of driving before he sobered up, that is enough.