The Supreme Court has mandated that in order for a police officer to pull a motorist over for a suspected DUI, the officer must have reasonable suspicion of illegal conduct. However, there is a great deal of disagreement about what constitutes reasonable suspicion that the driver has been drinking. The strength of "reasonable suspicion" varies from case to case but it may be a critical portion of your defense.
Why Were You Stopped?
In order to stop a vehicle, the law dictates that an officer must have “articulable and reasonable suspicion” that the driver is engaging in illegal activity. An officer may not pull a driver over just to check for license and registration; the officer must observe the driver engaging in behavior that indicates that the driver is breaking the law.
In DUI stops, officers can not pull you over just because you were leaving the area of a bar or because it is late at night. This may be their true motivation for a stop but they must rely on some driving behavior. Weaving within the lane over a substantial distance or weaving across lanes are both grounds for reasonable suspicion of DUI. Other reasons include driving too slowly, speeding, failure to signal, car equipment violations, and squealing tires. It is important to note that any of these observed behaviors can be disputed in court.
Many times I have found that the reason for the stop is a loose excuse at best. Driving too slowly can be caused by weather or traffic, weaving within the lane can be explained by ice on the road, there are even times where the listed reason for the stop is flat out false.
Challenge the Stop!
Do not just assume that the officer had good reason to pull you over, challenge the stop. If the stop is bad then you may have grounds to suppress any evidence obtained after the stop was performed (suppressed = can not be used against the defendant at trial). This could be the difference between a conviction and an acquittal.
For more information: William Young and Associates - Traffic Stop.