As the use of marijuana among people throughout Arizona as well as the rest of the country increases and the increasing legalization of recreational and medical marijuana, the number of drivers stopped, investigated and charged with DUI will also grow. Similar to an alcohol related DUI, police will initiate a motor vehicle stop once they observe a violation, look for signs of impairment and administer common field sobriety tests such as horizontal gaze nystagmus (HGN), the walk and turn test and one leg stand. Depending upon a person's driving behavior, performance of the field sobriety tests and other physical signs ad symptoms, officers will determine whether a driver should be arrested and ultimately seek a blood or urine sample to determine whether they have marijuana in their system.
Defenses to Marijuana Related DUI Charges
1. Differences in Types of Marijuana Metabolites
Although the State of Arizona does not distinguish between different types of metabolites when it comes to DUI, the Arizona Supreme Court has ruled that only psychoactive marijuana metabolites can lead to a DUI conviction. THC is the main psychoactive component of Marijuana which can cause impairment. However, THC can still be present in the blood for days after a person has used marijuana. Two common Marijuana metabolites are Hydroxy-THC and Carboxy-THC. While Hydroxy-THC can potentially cause impairment, Carboxy-THC is inactive and does not cause impairment. Consequently, the Arizona Supreme Court has stated that a person cannot be convicted of a marijuana DUI if their blood contains only Carboxy-THC or another non-impairing metabolite.
2. Medical Marijuana
Even if Hydroxy-THC, is found in your blood, medical marijuana cardholders may still have a defense to an Arizona DUI charge. The Arizona Supreme court allows medical marijuana users to argue that they: (1) used marijuana pursuant to the Arizona Medical Marijuana Act (AMMA) and (2) the marijuana or its metabolite was insufficient to cause impairment. Although this doesn't provide absolute immunity from a marijuana DUI prosecution for medical marijuana users, it does provide an affirmative defense. The defendant has the burden of proving by a preponderance of the evidence that the quantity of marijuana or metabolite was insufficient to cause impairment. At this point, there's not a specific quantity of marijuana or metabolite that everyone in the relevant scientific community agrees would cause impairment. Consequently, a thorough investigation of the DUI case, effective cross examination of the arresting officer and hiring a qualified expert to testify about THC levels and impairment is crucial to defending a marijuana related DUI charge.