Reasonable suspicion and probable cause in DUI investigations

Have you ever wondered about when can police officers pull you over? The answer is decidedly not “whenever they want to.” There is a legal rule for when an officer can stop a car: the officer must have reasonable suspicion that the motorist has committed a traffic offense or is involved in criminal activity.

That may seem like a straightforward requirement, but sometimes officers pull people over for suspicion that is not reasonable. For example, officers sometimes decide to rely on hunches or observations that another person would not find persuasive. When an officer is found not to have had reasonable suspicion before making a traffic stop, the evidence from that traffic stop is not admissible in court.

Examples of observations leading to reasonable suspicion of DUI

When it comes to a DUI arrest, the officer may have reasonable suspicion that the driver had been drinking. In other cases, they may simply observe a traffic violation and come to suspect intoxication during the traffic stop itself. For example, in most circumstances, an officer would have reasonable suspicion after observing a driver:

  • Weaving between lanes
  • Driving substantially below the speed limit
  • Straddling the center line
  • Driving erratically
  • Braking frequently
  • Nearly hitting something, such as another car
  • Stopping in traffic for no good reason
  • Driving with bright lights on

This is not a complete list. Any reasonably suspicious behavior is enough to justify a traffic stop. In addition, an officer may develop reasonable suspicion of impairment while investigating an accident or finding a driver asleep in a parked car.

Is reasonable suspicion enough to arrest someone?

No. Reasonable suspicion is only enough to pull a motorist over and investigate whether they have committed a traffic or other offense. In order to arrest the driver, the officer must meet a higher standard called “probable cause.” This means, more or less, that the officer has enough evidence to show that the driver has committed a crime. Only probable cause can justify an arrest.

The main difference is that reasonable suspicion involves believing that a motorist might have committed a traffic or criminal offense, while probable cause involves believing there is evidence that the driver probably did commit a crime.

If you get pulled over, you won’t be in a position to insist on reasonable suspicion or probable cause. These are issues for your attorney, but they could have a major impact on your case.

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