Before a law enforcement officer can arrest you for a DUI, they must have probable cause that you were driving under the influence to pull you over. This means that the police cannot simply stop you just to check if you are driving under the influence. It is in line with the Fourth Amendment that protects you from unreasonable searches and seizures whereby the police must point at specific facts that led them to believe that a crime was taking place.
However, it does not mean that the officer must specifically suspect that you are under the influence while driving. Provided that the officer can show cause for stopping you, that is enough. For instance, any traffic infraction is enough to pull you over.
Essentially, probable cause entails behavior that constitutes reasonable cause for a traffic stop. It may include:
If you have already been pulled over, probable cause for a DUI arrest can be an open container of alcohol in your car, the smell of alcohol on your breath, or other signs of drunkenness, as well as a verbal admission of intoxication.
In that case, it means that the evidence was obtained illegally. If the prosecution is relying on such evidence, you may file a motion to have it suppressed, which means that it cannot be used against you in the charges you are facing.
Learning what the law says will help you protect your rights throughout your case and increase the likelihood of a positive outcome for you.