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Arizona Marijuana DUI Laws (Updated 2020)

Arizona Marijuana DUI Laws:

The Definitive Guide (2020)


In this definitive guide, you will find:

  • The different ways you can be charged with a Marijuana DUI in plain english 
  • The meaning of a per se violation for prior use
  • Step-by-step guidance on how to use Medical Marijuana as a Defense  
Arizona Marijuana DUI


Different Marijuana DUI Offenses

Most people don’t realize that there is more than one way to violate Arizona’s Marijuana DUI laws in Arizona. Actually, there are two distinct ways the consumption of marijuana can result in a DUI under Arizona law. 

Description of Arizona Marijuana DUI Laws

In plain English, the law provides it’s illegal to drive (or be in actual physical control) of a car while either:

  • Impaired by marijuana, or
  • having a form of the drug in your body without a valid medical marijuana card.

However, if you drive after any potential effects of marijuana have subsided then it’s legal to drive with a medical marijuana card.  Arizona law has determined this is an affirmative defense.

Arizona Medical Marijuana Card

Accordingly, having a medical marijuana card is not a complete defense.  A valid card does not permit you to drive under the influence of marijuana to the point of impaired.

Here is the tricky part: law enforcement does not have a valid method to determine to impairment caused by marijuana.  They claim to have something called a “Drug Recognition Evaluation,” but it lacks any scientific validity. 

This is a little nuts:

Imagined you consume marijuana on a Sunday. However, you don’t have a medical marijuana card. 

The next day, well after the effects of the drug have worn off, you go to work. After putting in a full day’s work you drive home.  Under the current version of Arizona’s law, your prior use of Marijuana, results in a DUI – despite the fact you are not impaired…to any degree.


The Legal Danger of Prior Use

Arizona Marijuana DUI laws present a real risk of convicting innocent people from prior use.  A primary reason is legislation that contradicts what science tells us is true about the drug. However, recently much of the scientific reality about marijuana has made its way to a number of higher courts.  This includes the Arizona Supreme Court.  As a result, the current state of Arizona law provides that longer periods of prior marijuana use should not, alone, support a DUI conviction.

NHTSA Marijuana Impaired Driving (2017) for

Marijuana-Impaired Driving A Report to Congress

Thus, there are currently no evidence-based methods to detect marijuana-impaired driving.

NHTSA, Report to United States Congress, p. 13 (2017)

However, while many of the myths about the meaning of a positive marijuana test result have been discarded – the world views of the people that previously prosecuted such cases still remain.  These world views are plainly evident in the way some jurisdictions now prosecute alleged marijuana DUI cases based upon junk science.

NHTSA no evidence-based methods

While no reasonable person would advocate for a person to drive while impaired by a drug, what should be equally concerning is the wrongful prosecution of someone based up a scientific-sounding opinion lacking any basis in real science.  After all, the American justice system was founded on the fundamental principle that “it is far worse to convict an innocent man than to let a guilty man go free.” In re Winship, 397 U.S. 358, 372, 90 S. Ct. 1068, 1077, 25 L. Ed. 2d 368 (1970).

What is Marijuana?

In order to understand what the law prohibits we need to define some terms referenced by Arizona marijuana laws.  The includes what we commonly refer to as marijuana.

Marijuana or Cannabis?

Cannabinoid Types

What is the difference between marijuana and cannabis? For the most, part the answer is the people who use each term. Both labels refer to the same thing: the cannabis plant. Scientists use the term cannabis. The rest of us often use the term marijuana or slang version of the word.

Then there are also Cannabinoids

You may have also heard the term “cannabinoids.” The cannabis plant has an estimated over 400 chemicals. And over 60 of these chemicals, make up the class of chemicals called cannabinoids.

Cannabinoids interact with receptors within your central nervous system to produce their effects.



There are several subclasses of cannabinoids. For example:

  • Tetrahydrocannabinols (THC)
  • Cannabidiols (CBD)
  • Cannabigerols (CBG)
  • Cannabichromenes (CBC) 
  • Cannabinol (CBN)
  • Cannabinodiol (CBDL)
  • Cannabicyclol (CBL)
  • Cannabielsoin (CBE)
  • Cannabitriol (CBT)
THC, Tetrahydrocannabinol, medical marijuana

What is THC?

THC is Tetrahydrocannabinol. THC is one of the cannabinoids found in cannabis. THC is the primary psychoactive constituent of cannabis (delta 9-tetrahydrocannabinol, a.k.a ▵9_THC).  This the chemical that produces a “high” and can result in impairment. 

What does “pharmacokinetics” mean? 

The term describes how drugs (including alcohol) get into the body and then leave the body.  There are four (4) different phases of pharmacokinetics: Absorption, Distribution, Metabolism, and Elimination.

Metabolic Pathway of THC


Smoked Marijuana in Lungs
LUNGS: Smoking marijuana results in rapid absorption with peak THC plasma concentrations occurring prior to the end of smoking.


THC in the Stomach
STOMACH: Following oral administration, absorption is slower and has a more delayed peak in THC levels.
THC makes its way to the Heart
HEART: Smoking marijuana results in rapid absorption with peak THC plasma concentrations occurring prior to the end of smoking.
THC in the BRAIN
BRAIN: THC binds to cannabinoid receptors. It also interferes with cannabinoid neurotransmitter system.
THC to the Liver
LIVER: THC is metabolized in the liver. 

COLON: The majority of cannabis is excreted in feces.

KIDNEYS: Approximately 20% of cannabis is excreted in urine.

Marijuana Metbolites

After consuming marijuana (cannabis) it’s broken down by your liver. This is the process of drug metabolism. It is a process where your body alters the make up of a drug. Here is that process when you consume marijuana.


THC is the Primary Pschoactive Chemical

THC, called delta-9-THCis the psychoactive chemical in marijuana (cannabis). Enzymes in your live alter it into other substances called metobiltes.

What is Hydroxy-THC?

Think of Hydroxy-THC as the child created by THC.  Enzymes in your liver convert THC (delta-9-THC) into Hydroxy-THC (11-OH-THC).  

Hydroxy-THC is a psychoactive drug.  This means it is capable of causing impairment.

What is Carboxy-THC?

Consider Carboxy-THC as the grandchild of THC. It’s a secondary metabolite.  After being converted to Hydroxy-THC, it is eventually metabolized into Carboxy-THC.

Carboxy-THC is not psychoactive. It is not capable of causing impairment.



THC Molecule



Hydroxy THC





Critical Point:

The terms “ACTIVE” and “INACTIVE”  are often misunderstood and used in a misleading manner during the litigation of DUI cases.

For example, Hydroxy-THC is called an active metabolite of THC without further explanation.  This creates the FALSE ASSUMPTION that having an active metabolite in your body equals impairment. 

However, an active metabolite (like Hydroxy-THC) merely means you have a chemical in your body that was capable of causing impairment.

Drug Metabolism

Drug metabolism is what your body does to a drug to eliminate it.  It is also called xenobiotic metabolism. The rate of metabolism determines the duration of a drug’s pharmacologic action. 

Duration of Effects?

How long does marijuana affect​ you?

Based on a variety of factors marijuana affect each person differently.  However, typically the duration of its effects last approximately 3-5 hours. 

Duration of Impairment Marijuana

At the same time, some studies have detected THC in the blood at 30 days post-ingestion (Heustis, 2007). Accordingly, THC can be detected in your blood long after ingestion and long after the psychoactive effects of it have subsided. 

Marijuana Impairment

As reiterated by NHTSA, there are “currently no evidence-based methods to detect marijuana-impaired driving.” See, NHTSA, Report to United States Congress, p. 13.

Ishak v. McClennen (no universal limilt for drug impairment)
Ishak v. McClennen, 241 Ariz. 364, 368, ¶ 16, 388 P.3d 1, 5 (App. 2016) (unlike alcohol, there is no universal limilt for marijuana impairment)

Current knowledge about the effects of marijuana on driving is insufficient to allow specification of a simple measure of driving impairment outside of controlled conditions.

NHTSA, Report to United States Congress, p. 12 (2017)
NHTSA Marijuana Impaired Driving (2017) for

Marijuana-Impaired Driving A Report to Congress

The effects of alcohol consumption on things like judgment and cognition correlate well with an alcohol concentration.  However, the same is not true with marijuana. In the studies that have examined the relationship between THC levels and impairment have found that the level of THC in the blood and the degree of impairment do not appear to closely correlate.

  • No valid correlation between the pharmacologic effects of THC and its concentration in human blood.
  • Field Sobriety Tests done on roadsides were not designed, nor validated, for impairment. They are merely a screening test to help identify an alcohol concentration above a legal limit. 
  • THC affects the brain differently than alcohol.  A venous blood sample containing a THC concentration – is not the same as the brain THC concentration – at the time the blood sample is collected.
  • THC affects the brain differently than alcohol.  A venous blood sample containing a THC concentration – is not the same as the brain THC concentration – at the time the blood sample is collected.  A brain THC concentration can only be collected in post mortem samples.

The Problem of Per Se Arizona Marijuana DUI Laws

Most states, including Arizona, do not have a per se limit for a concentration of THC in DUI cases.  One potential reason likely has to do with the fact: frequent marijuana users will have a basal level of THC in their blood that often exceed 5 ng.



1. All of the candidate THC concentration thresholds examined would have misclassified a substantial number of driver as impaired who did not demonstrate impairment on the SFST, and would have misclassified a substantial number of drivers as unimpaired who did demonstrate impairment on the SFST

Based on this analysis, a quantitative threshold for per se laws for THC following cannabis use cannot be scientifically supported

2. Based on this analysis, a quantitative threshold for per se laws for THC following cannabis use cannot be scientifically supported.

Medical Marijuana Cards

Length of Permit

Arizona Medical Marijuana Act identification cards and registration certificates are now valid for two years instead of one year after the date of issue.

Sections amended: §§6-2801 36‐2803, 36-2804.01, 36-2804.05, 36-2804.06, 36‐2806,
36‐2810, 36‐2816, 36-2819. Sections added: §§36‐2803.01, 36‐2804.07, 36‐2820 and 36‐2821

Industrial Hemp

  • In the 2018 enactment is provides: that the propagation, manufacturing, distribution and market research is subject to regulation by the Department of Agriculture and violations of Title 3, Article 41 pertaining to industrial hemp are a Class 1 Misdemeanor.
  • Changed the effective date of laws regarding industrial hemp from August 1, 2019, to June 1, 2019.
  • It is also an affirmative defense to prosecution for possession or cultivation of marijuana if the accused is an industrial hemp licensee or designee or agent of a licensee in compliance with the statute.
  • It is not a defense to prosecution for possession, sale, transportation or distribution of marijuana if the product is not industrial hemp.

Emergency Clause, effective Date: February 20, 2019
Sections amended: Amends Laws 2018, Chapter 287, Section 7 and Section 9

Important Marijuana Case Law in Arizona

State v. Jones (2019)

Arizona Supreme Court held Cannabis Concentrates are Protected Under Arizona Medical Marijuana Act (AMMA).  The holding ruled something that was already seemingly obvious to most – the definition of marijuana goes beyond just lower and leaf form of the plant.  It also includes cannabis resin.

State v. Maestas (2018)

Adding to the list of locations where possession of marijuana is prohibited under the Arizona Medical Marijuana Act (AMMA, § 15-108(A)) violated the Voter Protection Act (VPA) and was unconstitutional as applied to AMMA-compliant marijuana users on a public college or university campus.

Ishak v. McClennen, 241 Ariz. 364, 388 P.3d 1 (App. 2016)

The Arizona Court of Appeals held:

  1. Precluding a defendant from offering evidence to support an affirmative defense that the marijuana metabolite concentration in his system was insufficient to cause impairment was erroneous;
  2. The lower court’s error was not harmless; and
  3. The defendant could establish defense by showing by a preponderance of the evidence that the marijuana metabolite concentration in his system was insufficient to cause him to be impaired at the time he operated or was in actual physical control of a vehicle.

Arizona Marijuana DUI Laws

Frequently Asked Questions

There are many legitimate signs and symptoms that a person may be impaired marijuana, but unfortunately, investigations often go well beyond actual science.  For example, law enforcement will often testify they a green tongue means a person is impaired by marijuana.  This proposition has no basis in science yet it taught by the National Highway Traffic & Safety Administration to officers across the United States.  One court that looked into NHTSA’s green tongue theory found:

State has presented nothing, no scientific studies and no case law or other authority, to support the reliability of the trooper’s concern regarding the condition of Hechtle’s tongueCf. State v. Wheeler, No. 24397–1–II, 100 Wash.App. 1062, 2000 WL 646511, *2 n. 2, 2000 Wash.App. LEXIS 779, *7 n. 2 (Wash.Ct.App. May 19, 2000) (“Although we assume the officer’s assertion to be true for the purposes of this opinion, we are nevertheless skeptical as to its accuracy. We find no case stating that recent marijuana usage leads to a green tongue.”). State v. Hechtle, 2004 UT App 96, ¶ 13, 89 P.3d 185, 190

Even the Arizona Court of Appeals has held the mere “scent of marijuana, standing alone, is insufficient evidence of criminal activity to supply probable cause for a search warrant.” State v. Sisco, 2 CA-CR 2014-0181, 2015 WL 4429575, at *1 (Ariz. Ct. App. July 20, 2015)

THC is also known as “Delta-9-tetrahydrocannabinol” and is the main psychoactive constituent in marijuana.

Hydroxy THC  is the primary metabolite of THC.

Cannabinoids are the active constituents in cannabis.

It is common knowledge that the higher your alcohol concentration, the more severe your intoxication. However, marijuana does not affect you the same as alcohol. The highest levels of the active part of marijuana (THC) are usually in your blood within about 3 to 10 minutes following inhalation. This does not mean the concentration of the drug will be at its highest level in that time frame. The concentration of THC in a blood sample simply has no correlation with a level of impairment.

Marijuana’s maximum influence on your performance usually manifests in 20 to 40 minutes after inhalation, yet this is also during the time period when your THC levels are rapidly falling. (Sewell et al., 2009).

Science has yet to meaningfully quantify how and to what extent marijuana impairs us.  While it is “well established that alcohol consumption increases accident risk, evidence of cannabis’ culpability in on-road driving accidents and injury is far less robust” (Armentano, 2013).

In sum, the presence of marijuana in your blood is simply not a reliable indicator of psychomotor impairment.

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