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Cruising the Highway: How to Avoid Getting Arrested and Convicted of a THC DUI – Part 1

Happy 2020! Hopefully everyone got through the holidays without getting a DUI. Sadly, this is a problem many cannabis consumers run into, including MMJ patients, because regardless of why a person may choose to consume cannabis, he or she will likely also choose to drive a car. Because of the rather severe consequences of a marijuana DUI conviction, it is important for all cannabis consumers, both patients and non-patients, to understand how to avoid being suspected, arrested and convicted of operating a motor vehicle while impaired by THC, the psychoactive component found in all plants of the genus cannabis. While I enjoy teaching at seminars to other defense attorneys about how to best defend against a THC DUI charge, this article is intended for the layman, for the non-lawyer. I will try to steer clear of legalese, lengthy case citations and other technical aspects and focus instead on providing practical information that will help the average Joe in the cannabis community avoid getting hemmed up in a DUI investigation. So, let’s get down to it.

First, let’s take a look at the pertinent statutes that a cannabis consumer needs to know about. A person who is arrested on suspicion of being impaired by THC will usually be charged with two types of DUI. The first kind is the generic DUI that is used to charge persons who are impaired by any substance capable of causing impairment. Codified at A.R.S. § 28-1381(A)(1), this kind of DUI makes it illegal to drive a motor vehicle in Arizona “[w]hile under the influence of alcohol or… any [other] drug… if the person is impaired to the slightest degree.” The prosecutor will attempt to prove the impairment through the driver’s appearance, behavior, performance on field sobriety tests, amount of THC in the driver’s blood, an admission to recently consuming cannabis, the presence of marijuana and paraphernalia in the vehicle, etc.

The second kind of DUI that a cannabis consumer will usually be charged with does not require proof of impairment at all. Instead this type of DUI makes it illegal to drive simply because the driver has THC or active THC metabolites in his system. A.R.S. §28-1381(A)(3) prohibits driving a vehicle “[w]hile there is any drug defined in § 13-3401 or its metabolite in the person’s body.” Cannabis is a drug found at A.R.S. § 13-3401(4) and marijuana is found at A.R.S. § 13-3401(19).

For many years the courts in Arizona allowed convictions to be based on the presence of even inactive THC metabolites (Carboxy-THC) and did not require the state to prove that the metabolites were active (hydroxy-THC) in order to sustain a conviction. This often led to persons being convicted of a DUI who last smoked marijuana up to 30 days earlier! Thankfully, in 2014, after decades of injustice, the Supreme Court of Arizona ruled in State v. Harris that the THC metabolites had to be active.

Still, active metabolites can remain in a person’s system for several days. This means that everyone who consumes cannabis every two or three days will always have THC or active THC metabolites in their system every time they get behind the wheel. In other words, practically every MMJ patient was still at risk. To fix this problem, myself and two other attorneys appealed to the Arizona Supreme Court in a case called State v. Dobson.

The Dobson case started in the Mesa Municipal Court, where the court rejected our argument for patient immunity from the marijuana metabolite law and was then appealed to the Maricopa County Superior Court and the Arizona Court of Appeals to no avail. Finally, at the Supreme Court, we were successful. The Supreme Court did not give us what exactly what we wanted most, however, which was complete immunity. Instead, they decided to give medical marijuana patients an affirmative defense to a marijuana metabolite charge. Specifically, the court held that it is a defense if the patient can prove at trial that the nanogram level of THC or active THC metabolites in his or her system was insufficient to cause impairment.

Dobson is a subjective standard, meaning that the patient driver does not have to prove that the level of THC was insufficient to cause anyone to be impaired. Rather, he or she need only prove that the level was insufficient to cause him personally to be impaired. This is significant because regular cannabis consumers develop tolerance and studies show that their safe driving skills improve when they are under the influence (more on this next month). Although it is not necessary to hire an expert witness to explain all this to the jury, it is very difficult to do so without one. And the states criminologist or other expert witness will not be of any help. In fact, they will often claim ignorance of helpful studies and exaggerate or misstate the research in order to help the prosecutor get a guilty verdict. Unfortunately, these expert witnesses are expensive and a patient driver who is charged with a marijuana metabolite DUI should plan on spending between $2,000 and $5,000. That is in addition to the attorney’s fees. Without an expert witness, however, the chances for acquittal are dramatically reduced. A trial can still be won, but the odds are much lower. But while it was an immense improvement over not having a defense at all, those with limited financial resources may not be able to afford both attorney and expert witness fees. This unfairness was our chief complaint about the Dobson decision.

The best strategy to winning a DUI charge is to not get arrested for DUI in the first place. Here are a few basic suggestions to patients that go a long way towards avoiding a DUI arrest. These are mostly self-evident but continue to be important factors in many DUI cases. I will go into more depth next month, but for now here are a few tips. First, don’t carry cannabis when driving a car. When the cop finds marijuana in the vehicle, it is easier for the state to convince a jury that you were smoking and driving, especially if they also find a pipe or rolling papers. If you must have your MMJ in the car then keep it out of harm’s reach to avoid a claim that you were smoking. If you are coming from a dispensary, keep the marijuana in the stapled bag with the receipt. And keep it in the trunk and/or in a odor proof container to minimize odor. Do not open until you get home. Finally, do not have your MMJ in plain view, like on the center console or passenger seat (it happens more than you would think).

Next month, I will discuss some additional issues pertaining to DUI stops in more depth, including when to exercise your right to remain silent and when to speak up, what to do when a cop says he smells marijuana, and how to handle field sobriety tests. Until then!

Click here for more from Tom Dean.

Tom Dean has been a criminal defense lawyer since 1993 and has been winning marijuana cases in Arizona for over 20 years. Tom has represented persons charged with every kind of marijuana offense, including cultivation, transportation, sales, extraction, DUI, and simple possession. For more information about Tom Dean, visit his website:


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