Illinois residents likely know that marijuana has been legalized for medical or recreational use in a number of states, and some road safety advocates are concerned that this could lead to a rise in traffic accidents involving impaired drivers. Determining marijuana impairment is usually done using blood tests, but a study conducted on behalf of AAA has concluded that blood testing for THC has no scientific merit.
According to the report, which was released by the automobile club’s safety foundation, testing a motorist’s blood for THC is not a reliable way to determine intoxication. Habitual users of marijuana develop a tolerance that could leave them unimpaired with blood THC levels that would render a casual user unable to drive. This means that basing DUI charges purely on THC testing could lead to innocent motorists being prosecuted while the guilty go free.
Another problem with these tests is the speed with which THC dissipates in the blood. Blood tests generally require a search warrant, and several hours may pass between a motorist being pulled over and blood being drawn. AAA recommends that THC blood testing be replaced by providing police officers with specialized training so that they are able to determine marijuana impairment based upon factors such as pupil dilation and tongue color.
The results of toxicology tests may not always be completely reliable, but they are scientific and impartial. Determining impairment based upon the opinion of police officers involves subjective judgment regardless of their specialized training, and criminal defense attorneys would likely argue vigorously that drunk driving charges be dismissed in cases where they are not supported by scientific evidence.