It is common for the police to base probable cause for a DUI stop on speeding, but occasionally, the police stop people for driving too slowly in order to see if they have been drinking. The CHP manual suggests that slow driving can be consistent with drunk driving as alcohol can slow reactions.

However, it should be argued that slow driving is not necessarily consistent with impaired driving and is not necessarily a traffic infraction unless the driver is impeding other traffic or otherwise causing a hazard to traffic. Each case should be looked at on its own facts. For example, driving within the lane at 30mph in a 40mph zone may be considered prudent driving. Driving at 20mph in a 40mph zone and impeding traffc would be the basis for a legitimate traffic stop. California Vehicle Code Section 22400(a) says that no person shall drive on a highway at such a slow speed as to impede or block the normal and reasonable flow of traffic, unless the speed is necessary for safe operation.

The proper way to challenge this evidence would be to file a 1538.5 motion attacking probable cause. If the initial traffic stop is ruled unlawful, the subsequest evidence of impairment including the results of any blood or breath test are suppressed and the case would normally be dismissed. Defending drunk driving charges on this basis requires the experience of a good DUI lawyer. 

If you have any questions about this or any other DUI related issue, call Los Angeles DUI Defense Lawyers Gold and Witham for a free consultation at 562 938 7771.