Thousands of motorists in Colorado are charged with driving under the influence or driving while ability impaired each year, and the vast majority of them are taken into custody following a routine traffic stop. Police officers in every state are only permitted to pull vehicles over when they have a reasonable suspicion that a crime has been committed. If they do not, they violate the protection against unreasonable government searches and seizures protected by the Fourth Amendment.
Traffic violations and erratic driving
Most of the traffic stops that lead to DUI/DWAI arrests are initiated by police officers who observe a vehicle violating a traffic law. Exceeding the posted speed limit and changing lanes without signaling are the violations that lead to traffic stops most often. Erratic driving also gives police officers a sufficient reason to pull a vehicle over, and they do not even have to witness it. If a motorist calls 911 to report a possible drunk driver, police officers can pull over the vehicle they describe without violating the Fourth Amendment.
Sobriety checkpoints seem to be at odds with the Fourth Amendment because drivers are stopped for no reason, but the U.S. Supreme Court has ruled them constitutional. The ruling was handed down in a case involving a Michigan man who was charged with drunk driving after being stopped at a sobriety checkpoint. The justices determined that protecting society form intoxicated drivers outweighed the other issues involved, and they described the infringement of the motorist’s Fourth Amendment rights as “negligible.”
Challenging traffic stops
Police officers usually respect the Fourth Amendment because they know that defendants are likely to challenge traffic stops that appear to violate it. When motorists are arrested on drunk driving charges, it is usually because they broke a traffic law, drove erratically or were stopped at a roadside sobriety checkpoint.