It is always surprising that so many people are stopped by the police and arrested for DUI when the reason they were stopped in the first place had nothing to do with DUI. I think more DUI arrests result from vehicle defects then from weaving.
The Fourth Amendment says that the police cannot stop you anytime they feel like it. They have to have a reason to stop you. The amount of evidence police must have to stop you depends on the situation. There are two levels of evidence that justify a stop. These are Reasonable and Articulable Suspicion, and Probable Cause.
Reasonable and Articulable Suspicion is the amount of evidence necessary to justify a belief that a person might be violating the law. That belief must be reasonable in the circumstances and based on evidence to support that reason. The officer must be able to articulate that reason as the reason for the stop. Also the reason for the stop must be related to the subsequent investigation. This means that the officer cannot just invent a reason as a pretext. The police cannot stop you on a mere hunch.
Probable Cause is the amount of evidence necessary to support a reasonable belief that a person has actually violated the law. It does not matter how technical the law is if there is a violation. This means that any defect in the vehicle is grounds to stop you. If you have a plate light out the police can stop you for that. If you have a Boston Red Sox plate on the front of your car instead of the registration plate, and you live in a state that requires to license plates that is a free stop, too.
If the stop is based on probable cause it doesn’t matter if it actually is a pretext to investigate for something else. This is why there are so many DUI cases that start with a vehicle defect. Police know that they can stop the car one of the morning if it has a plate light out, even if they don’t see any weaving or erratic operation. Usually the officer doesn’t really care about the plate light. He is stopping the car because he knows that one in the morning he has a good chance of finding someone who’s been drinking. He is really looking to arrest someone for DUI.
So what does that mean to most of us, who do not want to be stopped by the police just because the police feel like it? First, it means we better keep our cars in good working order. Make sure all the lights are working. Make sure there are no cracks in the windshield. Keep the car registered. Make sure it has an inspection sticker if your state requires one. Second, make sure that your car meets the requirements of the law. If your state says you must have two license plates, have two license plates, not just one.
Obviously, if you have been drinking the best thing to do is not drive. Even if you are not impaired or intoxicated, the mere smell of alcohol is enough to make the police think you are. Then they start the field sobriety tests and you are off to the races. Whether you pass or fail is completely subjective and they are the ones who get to decide. But if you are going to drink and then drive, you should drink responsibly–you also should keep your car in good working order.