An officer generally needs reasonable, articulable suspicion of a criminal offense or traffic violation to stop a vehicle. Without that basis, detaining a driver is not permitted except in certain limited circumstances.
A stop and an arrest involve different legal standards. A vehicle stop requires reasonable suspicion, while an arrest requires probable cause.
If an officer lacked the required legal basis, evidence collected as a result of the unlawful stop or arrest may be suppressed at trial. Suppressed evidence cannot be considered by the jury. Examining the basis for the stop and arrest is therefore an important part of DUI defense.