What is Reasonable Suspicion for a DUI Stop?

Although DUI checkpoints are a contentious exception (in most states), police officers can generally only stop drivers if they have reasonable suspicion of criminal activity. An officer with reasonable suspicion of a crime may stop and briefly detain a person for the purpose of conducting a limited investigation. If the officer still suspects the motorist of DUI after the initial investigation, a field sobriety test and/or a BAC (breathalyzer) test will be administered.

This means that every drunk driving arrest begins with an officer’s reasonable suspicion that the driver was involved in criminal activity, even if that suspicion is later disproved. Even if a driver is inebriated while driving, a DUI charge against him may be dismissed if the officer did not have reasonable suspicion at the time of the stop.

Reasonable Suspicion for a DUI Stop Examples

Any of the following observations could lead to a reasonable suspicion that a driver is impaired:

• Straddling the line in the middle
• Turn that isn’t legal
• Drifting from one lane to the next is a common occurrence.
• Almost colliding with other vehicles or objects on the roadside
• Driving that is excessively slow or erratic
• Braking is done frequently.
• Suddenly coming to a halt in the middle of the highway for no apparent reason

This is by no means a comprehensive list; anything that an officer suspects is a sign of intoxication may be considered reasonable suspicion. Similarly, if an officer has a reasonable suspicion that the driver is impaired after stopping for something completely unrelated, he may look into it further (a burned-out brake light, for example).

Probable Cause vs. Reasonable Suspicion

While reasonable suspicion allows an officer to temporarily stop and detain a driver in order to conduct further investigation if the officer suspects the driver of committing a crime, an officer must meet the higher standard of probable cause before making an arrest. Probable cause simply means that an officer has sufficient evidence to believe that a motorist has committed a crime, thus justifying his or her arrest. An officer may have probable cause for an arrest after administering a field sobriety test and/or a breath test in the context of a DUI stop if the results indicate probable intoxication.

Probable cause differs from reasonable suspicion in that an officer must have enough evidence to suggest that the motorist has most likely committed a crime in order to meet the probable cause standard. Reasonable suspicion, on the other hand, requires only that the officer has some evidence that the motorist has committed a crime. It’s a subtle distinction, but one that matters.