Although you are a medical marijuana patient, you can be arrested for a DUI if an officer suspects that you are under the influence of marijuana at the time of driving. Once you are in court, however, a marijuana-related DUI is difficult to prove without evidence; i.e. roaches, burnt smell, or officer sees you. Medical marijuana recommendation, or not, ALWAYS assert your right to remain silent and do not make statement about your smoking habits to the officers. However, if the officer has already found your medical marijuana, showing your recommendation is a good idea.