In Arizona a driver may legally ingest a particular controlled substance and then drive and be guilty of Driving Under the Influence even though the controlled substance has not impaired the driver, even to the slightest degree. That is because unlike for every other controlled substance, having a card for medical marijuana is not a defense to driving with a controlled substance in the driver’s body.
In recent times, though not without controversy, marijuana has become an accepted therapeutic drug in common use. Arizona, along with almost half of the states in the nation, has legalized at least in some fashion the use of marijuana for medical purposes. But the fact a drug is legal to use does not mean you are protected from charges of driving under the influence.
In Arizona whether a driver who has ingested marijuana is guilty or not guilty is determined by the status of the marijuana as it is in the driver’s blood when they are driving. If the marijuana is active, either as the medical compound of THC or one of its active metabolites, then the driver can be found guilty even though they may have a valid medical marijuana card. Fortunately as a result of a recent case from the Arizona Supreme Court, if the marijuana is present only as an inactive metabolite, meaning it is having no effect on the driver, then the driver is not guilty. The Court said in 2014, “We are not persuaded and reject the State’s argument that [the law] ‘creates a flat ban on the presence of any drug or its metabolite in a person’s body while driving or in actual physical control of a vehicle,’ even when the only metabolite found is not impairing…Because the legislature intended to prevent impaired driving, we hold that the ‘metabolite’ reference in [the law] is limited to any of a proscribed substance’s metabolites that are capable of causing impairment…Drivers cannot be convicted of the…offense based merely on the presence of a non-impairing metabolite that may reflect the prior usage of marijuana.” State ex rel. Montgomery v. Harris, 322 P. 3d 160.
Under 28 A.R.S. § 1381.a.3, a driver may lawfully drive with a controlled substance in their body as long as they were taking it as prescribed and it was not impairing them at all. This covers hundreds or even thousands of controlled substances. The only exception to this law is for marijuana because ingesting marijuana legally is not a defense if the marijuana is active in the driver’s blood.
A case is currently before the Arizona Supreme Court in which the court will decide if the legal use of marijuana should continue to be treated differently than all of the other prescribed controlled substances. In the meanwhile, the presence of active marijuana in a driver’s blood means the driver can be found guilty of Driving Under the Influence, even if they are not impaired to the slightest degree.