IN THE

SUPREME COURT OF THE STATE OF ARIZONA

KRISTINA R. DOBSON,

Petitioner,

v.

THE HONORABLE CRANE MCCLENNEN, JUDGE OF THE SUPERIOR COURT OF THE 

STATE OF ARIZONA, IN AND FOR THE COUNTY OF MARICOPA,

Respondent Judge,

CITY OF MESA PROSECUTOR’S OFFICE,

Real Party in Interest.

MARVELLE D. ANDERSON,

Petitioner,

v.

THE HONORABLE CRANE MCCLENNEN, JUDGE OF THE SUPERIOR COURT OF THE 

STATE OF ARIZONA, IN AND FOR THE COUNTY OF MARICOPA,

Respondent Judge,

CITY OF MESA PROSECUTOR’S OFFICE,

Real Party in Interest.

No. CV-14-0313-PR

Filed November 20, 2015

Appeal from the Superior Court in Maricopa County

The Honorable Crane McClennen, Judge

No. LC2014-000196 and LC2014-000266

AFFIRMED

Opinion of the Court of Appeals, Division One

236 Ariz. 203, 337 P.3d 568 (App. 2014)

VACATED
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

2

COUNSEL:

John P. Tatz (argued), John P. Tatz Attorney at Law, P.C., Glendale, 

Attorney for Kristina R. Dobson and Marvelle D. Anderson

W. Craig Jones (argued), Chief Assistant City Prosecutor, Mesa City 

Prosecutor’s Office, Mesa, Attorneys for City of Mesa Prosecutor’s Office

David J. Euchner (argued), Tucson, Attorney for Amicus Curiae Arizona 

Attorneys for Criminal Justice

Thomas W. Dean, Phoenix, Attorney for Amicus Curiae National 

Organization for the Reform of Marijuana Laws 

CHIEF JUSTICE BALES authored the opinion of the Court, in which VICE

CHIEF JUSTICE PELANDER and JUSTICES BRUTINEL, TIMMER, and 

BERCH (RETIRED) joined.

CHIEF JUSTICE BALES, opinion of the Court:

¶1 The Arizona Medical Marijuana Act (“AMMA”), passed by 

voters in 2010 and codified as A.R.S. §§ 36-2801-2819, allows a person who 

has been diagnosed by a physician as having a debilitating medical 

condition to apply for a card identifying the holder as a registered 

qualifying patient. Such patients may possess and use limited amounts of 

marijuana for medical reasons. The AMMA broadly immunizes them from 

prosecution for using medical marijuana consistent with the Act.

¶2 Arizona’s laws generally make it a crime for a person to drive 

with any amount of certain drugs, including marijuana or its impairing 

metabolite, in the person’s body. A.R.S. § 28-1381(A)(3); State ex rel. 

Montgomery v. Harris (Shilgevorkyan), 234 Ariz. 343, 347 ¶ 24, 322 P.3d 160, 

164 (2014). We today hold that the AMMA does not immunize a medical 

marijuana cardholder from prosecution under § 28-1381(A)(3), but instead 

affords an affirmative defense if the cardholder shows that the marijuana 

or its metabolite was in a concentration insufficient to cause impairment.
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

3

I.

¶3 Kristina Dobson and Marvelle Anderson (“Petitioners”) were 

each charged with two counts of driving under the influence (“DUI”). 

Count one alleged a violation of A.R.S. § 28-1381(A)(1), which prohibits a 

person from driving a vehicle in Arizona “[w]hile under the influence of ... 

any drug ... if the person is impaired to the slightest degree.” Count two 

alleged a violation of § 28-1381(A)(3), which prohibits driving a vehicle 

“[w]hile there is any drug defined in § 13-3401 or its metabolite in the 

person’s body.” Cannabis (marijuana) is a drug defined in A.R.S. § 13-

3401(4). Blood tests showed that each Petitioner had marijuana and its 

impairing metabolite in her body.

¶4 The municipal court denied Dobson’s motion to present 

evidence at trial that she held an Oregon-issued medical marijuana card 

and granted the State’s motion in limine to preclude evidence that 

Anderson held an Arizona-issued medical marijuana card. Neither

Petitioner sought to introduce any evidence other than their respective 

medical marijuana cards. The State dismissed the (A)(1) charges and 

Petitioners, after submitting the issue of guilt to the court based on a 

stipulated record, were each convicted of the (A)(3) charge.

¶5 Petitioners timely appealed to the Maricopa County Superior 

Court, which affirmed their convictions. They then sought special action 

review in the court of appeals, which accepted jurisdiction but denied relief. 

Dobson v. McClennen, 236 Ariz. 203, 205 ¶ 1, 337 P.3d 568, 570 (App. 2014). 

The court of appeals held that “neither A.R.S. § 36-2811(B) nor § 36-2802(D) 

provides immunity for defendants facing charges for driving with an 

impermissible drug or impairing metabolite in their bodies under A.R.S. 

§ 28-1381(A)(3).” 263 Ariz. at 209 ¶ 20, 337 P.3d at 574.

¶6 We granted review because whether the AMMA immunizes 

a medical marijuana cardholder from DUI prosecution under § 28-

1381(A)(3) presents a recurring issue of statewide importance. We have 

jurisdiction under Article 6, Section 5(3) of the Arizona Constitution and 

A.R.S. § 12-120.24.
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

4

II.

¶7 We review questions of statutory interpretation de novo. 

State v. Hansen, 215 Ariz. 287, 289 ¶ 6, 160 P.3d 166, 168 (2007). A reviewing 

court’s “primary objective in construing statutes adopted by initiative is to 

give effect to the intent of the electorate.” State v. Gomez, 212 Ariz. 55, 57 

¶ 11, 127 P.3d 873, 875 (2006). “When two statutes conflict, we adopt a 

construction that reconciles them whenever possible, giving force and 

meaning to each.” State v. Jones, 235 Ariz. 501, 502 ¶ 6, 332 P.3d 191, 192 

(2014).

A.

¶8 The AMMA broadly immunizes registered qualifying 

patients for their medical use of marijuana, providing: 

A registered qualifying patient . . . is not subject to arrest, 

prosecution or penalty in any manner, or denial of any right 

or privilege, including any civil penalty or disciplinary action 

by a court or occupational or professional licensing board or 

bureau: (1) For the registered qualifying patient’s medical use 

of marijuana pursuant to this chapter, if the registered 

qualifying patient does not possess more than the allowable 

amount of marijuana. 

A.R.S. § 36-2811(B)(1). 

¶9 This grant of immunity is not absolute. For instance, the 

AMMA does not prohibit prosecution for “[o]perating, navigating or being 

in actual physical control of any motor vehicle, aircraft or motorboat while 

under the influence of marijuana.” A.R.S. § 36-2802(D). However, “a 

registered qualifying patient shall not be considered to be under the 

influence of marijuana solely because of the presence of metabolites or 

components of marijuana that appear in insufficient concentration to cause 

impairment.” Id.

¶10 Arizona’s DUI laws identify separate offenses for driving

while a person is under the influence of marijuana and “impaired to the 

slightest degree,” A.R.S. § 28-1381(A)(1), and driving while there is 

marijuana or its metabolite “in the person’s body.” § 28-1381(A)(3). An 

(A)(3) violation, unlike an (A)(1) violation, does not require the state to 
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

5

prove that the defendant was in fact impaired while driving or in control of 

a vehicle. Harris, 234 Ariz. at 347 ¶ 24, 322 P.3d at 164. Instead, marijuana 

users “violate (A)(3) if they are discovered with any amount of THC or an 

impairing metabolite in their body.” Id.

¶11 The (A)(1) and (A)(3) offenses also differ with respect to 

possible defenses. When the state charges a person with driving while

impaired by drugs in violation of (A)(1), “[i]t is not a defense . . . that the 

person is or has been entitled to use drugs under the laws of this state.” 

§ 28-1381(B). In contrast, a person cannot be convicted under (A)(3) for 

using a drug as prescribed by a licensed medical practitioner. A.R.S. § 28-

1381(D). Subsection (D) thus provides an affirmative defense to an (A)(3) 

charge.

¶12 In Harris, we held that “[d]rivers cannot be convicted of the 

(A)(3) offense based merely on the presence of a non-impairing metabolite 

that may reflect the prior usage of marijuana.” 234 Ariz. at 347 ¶ 24, 322 

P.3d at 164. Although we observed that “a driver who tests positive for any 

amount of an impairing drug is legally and irrefutably presumed to be 

under the influence,” id. at 347 ¶ 22, 322 P.3d at 164, in Harris we did not 

consider the scope of the subsection (D) affirmative defense. Nor did that 

case involve a driver who was a qualified registered patient.

¶13 Here, we must resolve how the AMMA affects (A)(3) 

prosecutions. The State argues that the AMMA, which provides that a 

registered card holder cannot be considered to be under the influence of 

marijuana if it is present in an “insufficient concentration to cause 

impairment,” § 36-2802(D), does not affect (A)(3) prosecutions at all 

because the State is not required to prove a defendant’s impairment to 

establish an (A)(3) violation. Dobson and Anderson counter that the 

AMMA immunizes them from an (A)(3) prosecution because they cannot 

be considered to be under the influence based solely on the mere presence 

of marijuana or its metabolite in their bodies. They also contend that the 

affirmative defense afforded by § 28-1381(D) applies to them.

¶14 Neither position urged by the parties represents the best 

reading of the statutory provisions. The State’s view effectively renders

superfluous the “shall not be considered to be under the influence” clause 

in A.R.S. § 36-2802(D). This language would be unnecessary if it only 

prohibited prosecution under statutes, such as § 28-1381(A)(1), that require 
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

6

the state to prove that the defendant is in fact impaired as a result of the 

presence of marijuana or its metabolite. Section 36-2802(D) is more 

plausibly interpreted as applying to statutes like § 28-1381(A)(3), which, as 

we noted in Harris, presume that a defendant is impaired based on the mere 

presence of any amount of marijuana or its potentially impairing 

metabolites in a person’s body. 234 Ariz. at 347 ¶ 22, 322 P.3d at 164.

¶15 Petitioners, however, are also not convincing in arguing that 

§ 36-2802(D) immunizes registered qualifying patients from any

prosecution under § 28-1381(A)(3). Section 36-2802(D) does not say that 

registered qualifying patients cannot be prosecuted for (A)(3) violations. 

Instead, it provides that such patients, who use marijuana “as authorized” 

by the AMMA, id. § 36-2802(E), cannot “be considered to be under the 

influence of marijuana solely because of the presence of metabolites or 

components of marijuana that appear in insufficient concentration to cause 

impairment.” Id. § 36-2802(D) (emphasis added).

¶16 Violations of § 28-1381(A)(3) include, but are not limited to, 

situations in which drivers have a non-impairing amount of certain drugs 

in their bodies. This reflects that the legislature, in seeking to combat the 

serious problem of impaired driving, recognized that for certain drugs it 

may be difficult to identify concentrations that definitively establish 

whether a defendant is impaired. Harris, 234 Ariz. at 347 ¶ 22, 322 P.3d at 

164; cf. A.R.S. § 28-1381(A)(2) (proscribing driving with an alcohol 

concentration of .08 or more irrespective of proof of actual impairment). 

Thus, the (A)(3) offense does not require the state to prove that the 

defendant is in fact impaired “to the slightest degree,” § 28-1381(A)(1), but 

instead requires the state to prove that the defendant has been driving or in 

control of a vehicle while any amount of the proscribed drugs or their 

impairing metabolites are present “in the person’s body.” Id. 28-1381(A)(3); 

Harris, 234 Ariz. at 347 ¶ 24, 322 P.3d at 164.

¶17 Section (A)(3) thus casts a net that embraces drivers who have 

proscribed drugs or their impairing metabolites in their bodies but who 

may or may not be impaired. By its terms, § 36-2802(D) does not shield 

registered qualifying patients from prosecution under (A)(3), but instead 

says they cannot be considered to be “under the influence” based solely on 

concentrations of marijuana or its metabolites that are insufficient to cause 

impairment. When read together, the statutory provisions suggest that the 
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

7

AMMA gives qualifying patients a limited defense rather than a general 

immunity in (A)(3) prosecutions.

¶18 We reject, however, Petitioners’ argument that qualifying 

patients can rely on the defense afforded by § 28-1381(D) for the use of 

prescribed drugs. Medical marijuana used pursuant to “written 

certifications” under the AMMA is not “prescribed,” see A.R.S. §§ 36-

2801(18), -2804.02(A)(1); and the § 28-1381(D) defense applies to drugs 

prescribed by a different class of licensed “medical providers” than those 

who may issue medical marijuana certifications. Compare A.R.S. § 28-

1381(D) (defining “medical providers” as including licensed podiatrists, 

dentists, medical doctors, and osteopathic physicians) with § 36-2801(12)

(defining “physician” as including licensed medical doctors and 

osteopathic, naturopathic, and homeopathic physicians).

¶19 Section 36-2802(D), rather than § 28-1381(D), defines the 

affirmative defense available to a registered qualifying patient to an (A)(3) 

charge. If their use of marijuana is authorized by § 36-2802(D), such 

patients cannot be deemed to be under the influence – and thus cannot be 

convicted under (A)(3) - based solely on concentrations of marijuana or its 

metabolite insufficient to cause impairment. Possession of a registry card 

creates a presumption that a qualifying patient is engaged in the use of 

marijuana pursuant to the AMMA, so long as the patient does not possess 

more than the permitted quantity of marijuana. A.R.S. § 36-2811(A)(1). 

That presumption is subject to rebuttal as provided under § 36-2811(2).

¶20 A qualifying patient may be convicted of an (A)(3) violation 

if the state proves beyond a reasonable doubt that the patient, while driving 

or in control of a vehicle, had marijuana or its impairing metabolite in the 

patient’s body. The patient may establish an affirmative defense to such a 

charge by showing that his or her use was authorized by the AMMA -

which is subject to the rebuttable presumption under § 36-2811(2) - and that 

the marijuana or its metabolite was in a concentration insufficient to cause 

impairment. The patient bears the burden of proof on the latter point by a 

preponderance of the evidence, as with other affirmative defenses. See 

A.R.S. § 13-205 (“[A] defendant shall prove any affirmative defense raised 

by a preponderance of the evidence.”).

¶21 Petitioners contend that it is inappropriate to assign to 

qualifying patients the burden of showing that they did not have marijuana 
DOBSON V. MCCLENNEN (MESA PROSECUTOR)

Opinion of the Court

8

concentrations sufficient to cause impairment because there is no

commonly accepted threshold for identifying such concentrations. Cf. 

Harris, 234 Ariz. at 347 ¶ 22, 322 P.3d at 164 (noting that “there is no 

generally applicable concentration that can be identified as an indicator of 

impairment for illegal drugs”). This contention, however, argues in favor 

of assigning the burden to patients to prove, by a preponderance, that the 

marijuana concentration in their bodies while they were driving was not 

sufficient to cause impairment. The risk of uncertainty in this regard should 

fall on the patients, who generally know or should know if they are 

impaired and can control when they drive, rather than on the members of 

the public whom they encounter on our streets. Cf. Harris, 234 Ariz. at 346

¶ 20, 322 P.3d at 163 (noting state’s compelling interest in protecting public 

from drivers who may be impaired by consumption of controlled 

substances).

B.

¶22 Petitioners made no effort to show that the marijuana in their 

bodies was in an insufficient concentration to cause impairment. Instead, 

they argued that the AMMA categorically barred the (A)(3) charge, and 

they offered only their respective registry identification cards into evidence. 

Although evidence of possession of a registry card would generally be 

admissible in an (A)(3) prosecution to invoke the presumption that the 

patient was using marijuana pursuant to the AMMA, it does not suffice to 

establish the § 36-2802(D) affirmative defense. Any error by the trial court

in excluding evidence of the registry cards was harmless in light of the 

stipulations by Petitioners that they had marijuana in their bodies while 

driving (blood tests revealed both THC and its impairing metabolite 

hydroxy-THC) and their failure to offer any evidence that the 

concentrations were insufficient to cause impairment.

III.

¶23 Rather than shielding registered qualifying patients from any 

prosecution under A.R.S. § 28-1381(A)(3), the AMMA affords an 

affirmative defense for those patients who can show, by a preponderance 

of the evidence, that the concentration of marijuana or its impairing 

metabolite in their bodies was insufficient to cause impairment. We vacate 

the opinion of the court of appeals and affirm the Petitioners’ convictions.