What are the valid grounds for a police officer to stop a vehicle?
For any law enforcement officer to have a valid reason to stop you in your vehicle there must be a "articulable and reasonable suspicion" that:
(1) you are an unlicensed driver;
(2) that your vehicle is not registered;
(3) either you are a "wanted" person on a criminal charge or the vehicle you are driving is in violation of the law.
What is "articulable" and what is "reasonable"?
"Articulable" means the law enforcement officer is able to verbalize specific facts and reasons to the court, through testimony, a reason why he or she believed a violation of the law existed that would justify the stop of your vehicle. What constitutes "reasonable" is analyzed on a case by case basis, but it typically has to be more than a mere "hunch" or guesswork on the part of the officer.
Examples of traffic stops courts have found to be NOT reasonable
As an example, the following traffic stops by police officers have been ruled to be NOT reasonable: (1) if you stopped near a construction site where crimes had occurred before, got out of your car and walked around for a few minutes; (2) if you were just driving below the posted speed limit but not impeding traffic; or (3) if you were weaving slightly in your vehicle when no other vehicles were around. "Laying drag" (white smoke coming from squealing and spinning tires) in the midst of heavy vehicular and pedestrian traffic is an adequate reason to stop your vehicle. The officers must have some reasonable and articulable suspicion that you are committing a crime before they decide to stop you, not just develop this suspicion after your stop.
You can challenge an arrest and criminal charge based on an illegal "stop" of you and your vehicle
In your DUI-DWI case, you thus have a possible legal challenge to the basis of the "stop" or confrontation by the police if the law enforcement officer who initially stopped you, or discovered you intoxicated in your stationary vehicle, cannot give the court a good reason for the stop or for interrupting your privacy. Because each case is fact-specific, most of these challenges are won on extremely minor evidentiary points that are brought out by your criminal defense specialist at a pre-trial motion.
"Stationary Shelter" Defense
An example of this type of affirmative defense is the "stationary shelter" defense. Used mostly in northern states, this is the situation where you may have left a bar or tavern in a very intoxicated state. You have to go somewhere at 4am after you have been drinking, and the warmth of the inside of your car may be the difference between freezing to death and surviving until you are sober enough to drive. While you may be found by the police in the front seat of your vehicle, and still in an intoxicated state, some courts have suggested that the appropriate legal test should be whether you posed a threat to the public by your exercise of present or imminent control over your vehicle while impaired, rather than simply using your vehicle as a stationary shelter. If your attorney is able to show the weather conditions were such that your car was the only shelter between you and death, and that there was no evidence that you intended to drive intoxicated, your arrest may not be valid.