Arizona DUI prohibits driving while impaired by alcohol or drugs. This holds true even when the impairing substance is legally consumed. For Instance, under Arizona law, drivers can be convicted of DUI for driving with legal persecription drugs in one's body if those drugs have impaired the driver's ability to drive to the slightest degree. The fact the drugs were legally prescribed is not a defense.
What About Illegal Drugs or Unauthorized Use of Prescription Drugs?
Under ARS 28-1381(A)(3), people can be charged with DUIs when they operate motor vehicles with any drug listed in ARS § 13-3401 or its metabolite. This subsection is a zero-tolerance law because you can be arrested if you have any amount of a listed drug in your system, even if you are not impaired. So if a driver consumes a small amount of illegal cocaine the driver can be found guilty, even if the cocaine is not impairing the driver.
What About Marijuana? Isn't It Legal?
Marijuana is one of the drugs listed under ARS § 13-3401, along with heroin, cocaine, methamphetamines, and prescription drugs when you do not have a valid prescription.
Even though Marijuana is on the list, on Nov. 30, 2020, Arizona voters passed Proposition 207, legalizing the recreational use of marijuana. Under Proposition 207, adults 21 and older are allowed to possess, use, and transport small amounts of marijuana. Proposition 207 also overrides A.R.S. § 28-1381(A)(3) as Proposition 207 specifically states a person who has marijuana or its metabolites in their system cannot be convicted of a DUI under ARS 28-1381(A)(3) unless they are impaired to the slightest degree. The language effectively makes marijuana based DUIs filed under ARS 13-1381(A)(3) the same as a generic DUI filed under ARS 28-1381(A)(1).