DRIVING UNDER THE INFLUENCE OF MARIJUANA
Just as it is illegal to drive under the influence of alcohol, it is illegal to drive under the influence of marijuana. It does not matter if the driver has a Medical Marijuana Identification Card; it is still a violation to drive while under the influence of any substance, including marijuana, if that substance affects your ability to drive safely. The statute itself is vague and requires the subjective observations of the officer.
An arrest for driving under the influence of marijuana is treated much the same as an arrest for drunk driving except that the arresting officer will not suspend the driver’s license to drive immediately upon arrest. However, if the driver is convicted of the charge, the court will inform the DMV of the conviction and the DMV will proceed on suspension of the driver’s license to drive and the driver will be required to take DUI classes.
But just how does the prosecution prove that someone was driving under the influence of marijuana? After the arrest, the driver’s blood or urine will be tested for the presence of THC (tetrahydrocannabinol). But detection of THC in a person’s system does not establish evidence that the driver was impaired by this substance. The compound THC, which is the chemical that causes a person to get “high” on marijuana, can stay in a person’s system long after the high has worn off. In fact, THC can stay in a person’s system for days. Therefore, it is not enough for the prosecution to establish that the person had THC in his or her system at the time of the arrest, there must be a connection between the THC levels detected in the driver’s system and his or her driving impairment. Even the National Highway Traffic Safety Administration has stated that it is difficult to establish the effects of THC in a person’s blood and his or her driving performance.
Often the prosecution must rely on circumstantial evidence such as the driver’s behavior or appearance when he or she was stopped (e.g., bloodshot eyes, slowed speech, etc.) or perhaps other evidence the officer writes up in the arrest report. The smell of freshly burnt marijuana in the car plus a chemical test indicating THC in the driver’s system is most often the type of circumstantial evidence that will result in a conviction. But without solid evidence, the prosecution is in a weak position and with the right defense the prosecutor will often allow the driver to plea to a lesser charge or even dismiss the charge.
True, a driving under the influence of marijuana can be difficult to prove, but the consequences of a conviction on this charge are more than a minor inconvenience. And even when the charge is based on weak evidence, the prosecution often will still enthusiastically pursue a conviction. It goes without saying that it is important for anyone arrested for allegedly driving under the influence of marijuana to consult with an attorney with experience in these matters. He or she can identify the weaknesses in the prosecution’s case and while every case has its own evidence, an experienced attorney can readily assess the facts and discuss the best defense options available based on the particulars of each case.
“It is unlawful for a person who is under the influence of any drug to drive a vehicle.” (Cal. Veh. Code §25152(e).)
 National Highway Traffic Safety Administration (NHTSA), Drug and Human Performance Fact Sheet.