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 Maryland, DUI (driving under the influence) and DWI (driving while impaired) laws can apply to individuals who are in 'physical control' of a vehicle, even if they are not actually driving. This means that a person who is sitting, lying, or sleeping in their vehicle while under the influence could potentially face DUI/DWI charges if they are deemed to be in physical control of the vehicle. Factors that law enforcement may consider include the person's location in the vehicle (driver's seat vs. passenger seat), whether the vehicle's engine is running, the person's state (awake or asleep), and the location of the vehicle's keys. If the police find someone in such a situation, they may conduct a welfare check, and if there is suspicion of impairment, they may ask questions, request a breath or blood test, administer field sobriety tests, and potentially arrest the individual for DUI/DWI. It is important for individuals to understand that even without driving, being in physical control of a vehicle while impaired can lead to legal consequences.