Are You a Legal Professional?

What is Reasonable Suspicion for a DUI Stop?

Although DUI checkpoints remain a controversial exception to the rule (in most states), police officers can generally stop motorists only when they have reasonable suspicion of criminal activity. An officer who has reasonable suspicion that a crime has taken place may stop and briefly detain an individual for the purpose of a limited investigation. If the officer still suspects the motorist of DUI after the initial investigation, the officer will then usually carry out a field sobriety test and/or a BAC (breathalyzer) test.

This all means every arrest for drunk driving begins with an officer's reasonable suspicion that the motorist was involved in some sort of criminal activity, even if that turns out not to be the case. Even if a motorist is intoxicated while driving, a DUI case against him could be dismissed if the officer did not have reasonable suspicion for the initial stop.

See "DUI Arrests" to learn more about your rights and responsibilities with respect to drunk driving, including traffic stops and sobriety tests.

Examples of Reasonable Suspicion for a DUI Stop

Reasonable suspicion that a motorist is impaired may by established by any of the following observations:

  • Straddling the center line
  • Illegal turn
  • Drifting from one lane to another
  • Nearly hitting other cars or objects on the roadside
  • Extremely slow or erratic driving
  • Frequent braking
  • Stopping in the middle of the road for no apparent reason

This is by no means a complete list, as anything an officer believes is a sign of impaired driving might possibly be considered reasonable suspicion. Likewise, an officer may investigate further if he has a reasonable suspicion that the driver is impaired after making a stop for something entirely unrelated (a burned-out brake light, for example).

In some cases, reasonable suspicion for a DUI stop may be established even if the officer did not witness any actual driving. For example, an officer may conduct a field sobriety test after an automobile accident or if a motorist is found unconscious behind the wheel of a parked car.

Reasonable Suspicion vs. Probable Cause

While reasonable suspicion allows an officer to temporarily stop and detain a motorist in order to investigate further if the officer thinks the motorist may have committed a crime, an officer must meet the higher standard of probable cause before making an arrest.  Probable cause simply means that an officer has enough evidence to believe a motorist has probably committed a crime, thus justifying his or her arrest. In the context of a DUI stop, an officer could have probable cause for an arrest after administering a field sobriety test and/or a breath test if the results point to probable intoxication. 

Probable cause differs from reasonable suspicion in that, in order to meet the probable cause standard, an officer must have enough evidence to suggest that the motorist has most likely committed a crime.  Reasonable suspicion, on the other hand, only necessitates that the officer have some indication that the motorist might have committed a crime.  It is a fine distinction, but an important one.

Next Steps
Contact a qualified DUI attorney to make sure
your rights are protected.
(e.g., Chicago, IL or 60611)

Help Me Find a Do-It-Yourself Solution