San Diego DUI Law Center

What Counts as Reasonable Suspicion in a DUI Investigation?

In order for San Diego law enforcement to stop you for driving under the influence (DUI), they must have reasonable suspicion you have committed such a crime. If an officer has reasonable suspicion, they can conduct a brief field investigation. If further evidence of a DUI is noticed, the officer may be inclined to request you to submit to a field sobriety test.


Reasonable Suspicion

Reasonable suspicion; is a legal standard of proof in the United States that is less than probable cause. Probable cause is the legal standard for arrests and warrants. It is more than an “inchoate and unparticularized suspicion or ‘hunch'”. It must be based on “specific and articulable facts”, “taken together with rational inferences from those facts”. The suspicion must be associated with the specific individual. In short, reasonable suspicion is the facts and circumstances that lead law enforcement to believe an individual committed a criminal act.


Common causes of reasonable suspicion include:

  • Driving across the center line
  • Stopping without reason
  • Driving significantly under the speed limit
  • Braking frequently
  • Driving significantly over the speed limit
  • Drifting through lanes
  • Almost causing an accident


Without reasonable suspicion, an arrest cannot lawfully be made on the grounds of a DUI.


Probable Cause

Probable cause is not the same thing as reasonable suspicion. Reasonable suspicion is generally needed for an officer to start a DUI investigation. On the other hand, reasonable suspicion is needed for an officer to make a lawful arrest. Probable cause requires a much stricter standard of evidence than reasonable suspicion.


DUI Checkpoints

DUI checkpoints are an exception. At a checkpoint, officers stop every vehicle without having reasonable suspicion at all. The Supreme Court has declared that DUI checkpoints are a permissible exception to the reasonable suspicion rule.


Illegal DUI Stop/Arrest

What can you do if you were stopped and/or arrested for a DUI without reasonable suspicion? Ultimately, the defendant would need to file a motion to suppress evidence in court. If the motion to suppress is successful, it can lead to a dismissal of the DUI charge. Filing a motion to dismiss is just one of the ways a defendant can refute an illegal DUI stop or arrest. For more ways to combat a DUI stop or arrest without reasonable suspicion, you should talk with a California DUI Lawyers Association designated Specialist.


Talk to a DUI Attorney

Above all, with the law constantly changing in regard to fact-specific inquiries, it is best to talk with an attorney to make sure you are made aware of all of your options. California DUI Lawyers Association designated Specialist, Rick Mueller, will ensure you are informed and get the best possible outcome.


This is a glimpse into what counts as reasonable suspicion in a DUI investigation.

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