A person who believes they have had too much to drink to safely or legally drive may sit, lie, or fall asleep in their vehicle in a parking lot or parking space outside of a bar or restaurant, or may pull off the road and park to “sleep it off.” When the police observe a person occupying or sleeping in a parked car they may investigate if the car is illegally parked (on the side of the road or elsewhere) or for the stated purpose of checking on the well-being of the occupant of the vehicle.

After knocking on the window and attempting to wake the occupant of the vehicle the police will typically ask if the occupant was recently operating the vehicle and whether the occupant has had anything to drink. Based in part on the occupant’s answers to these questions the police may request the occupant submit to a breath or blood test, perform field sobriety tests, and may ultimately arrest the occupant for DUI/DWI.

Laws defining DUI/DWI criminal offenses vary from state to state and often include a person who is in physical control of a vehicle as being within the definition of operating a vehicle. Based on such a broad statutory definition of operating a vehicle—and depending on other factors such as (1) whether the occupant was in the driver’s seat of the vehicle or the back seat or passenger seat; (2) whether the vehicle’s engine was running; (3) whether the occupant was awake or asleep; and (4) whether the key, if any, was in the ignition—the police may arrest the occupant for DUI/DWI.

In Montana, DUI (driving under the influence) laws are set forth under Montana Code Annotated (MCA) 61-8-401 et seq. These laws prohibit operating or being in actual physical control of a vehicle while under the influence of alcohol or drugs. Actual physical control means that an individual has the ability to operate the vehicle, regardless of whether they are driving it at the time. This can include situations where a person is found in a parked vehicle with the potential to drive. Factors such as the person's location in the vehicle, whether the engine is running, the occupant's state (awake or asleep), and the position of the keys can all influence whether an individual is considered to be in actual physical control of the vehicle. If the police find someone in a parked car who appears to have been drinking, they may investigate and potentially arrest the individual for DUI if they believe the person has the ability to drive the vehicle. It is important for individuals to be aware that even if they are not driving, being in a parked car while intoxicated can still lead to DUI charges if they are deemed to be in physical control of the vehicle.