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 New Hampshire, DUI/DWI laws can apply to a person who is in 'actual physical control' of a vehicle, even if they are not driving at the time. This means that if someone is sitting, lying, or sleeping in their vehicle and exhibits signs of impairment, they could potentially be charged with DUI/DWI. Factors such as the person's location in the vehicle, whether the engine is running, their state of consciousness, and the position of the keys can all influence whether they are considered to be in control of the vehicle. If the police find someone in a parked car and suspect they have been drinking, they may conduct an investigation that can include questioning, breath or blood tests, and field sobriety tests. Depending on the outcome of these assessments, the individual could be arrested for DUI/DWI. It's important to note that simply being in a parked car does not automatically result in DUI/DWI charges, but the circumstances can lead to an arrest if the police have reason to believe the person has control over the vehicle while impaired.