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 Mississippi, DUI laws are such that a person can be charged with DUI if they are found to be in 'actual physical control' of a vehicle while under the influence of alcohol or drugs. This means that even if a person is not driving but is in the driver's seat with the keys in the ignition, or if the engine is running, they could potentially be charged with DUI. The specific circumstances, such as the location of the person within the vehicle, whether the vehicle is legally parked, and whether the person is awake or asleep, can all influence the decision of law enforcement to investigate and potentially arrest for DUI. If the police find someone sleeping in their car, they may conduct a welfare check and inquire about recent vehicle operation and alcohol consumption. Refusal to submit to a breath or blood test can lead to immediate license suspension under Mississippi's implied consent laws. It is important for individuals to be aware that trying to 'sleep it off' in a vehicle can lead to legal consequences if they are deemed to be in physical control of the vehicle while impaired.