There are two types of DUI offenses involving marijuana. First, a person can be chared with DUI if there is probable cause to believe that he operated a motor vehicle while “impaired to the slightest degree” by marijuana. Secondly, a person is in violation of DUI law if he or she operates a vehicle with any trace of marijuana in his or her system as detected by THC metabolites in bodily fluids. Here is the statute:
Arizona Revised Statute (A.R.S.) 28-1381 (in pertinent part)
A. It is unlawful for a person to drive or be in actual physical control of a vehicle in this state under any of the following circumstances:
1. While under the influence of intoxicating liquor, any drug, a vapor releasing substance containing a toxic substance or any combination of liquor, drugs or vapor releasing substances if the person is impaired to the slightest degree.
3. While there is any drug defined in section 13-3401 or its metabolite in the person’s body.
B. It is not a defense to a charge of a violation of subsection A, paragraph 1 of this section that the person is or has been entitled to use the drug under the laws of this state.
D. A person using a drug, as prescribed by a medical practitioner licensed pursuant to title 32, chapter 7, 11, 13 or 17 is not guilty of violating subsection A, paragraph 3 of this section.