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Court: Medical marijuana no free pass for driving impaired

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PHOENIX — People with marijuana in their system can escape drugged-driving charges if they can show they weren’t “high” enough to be impaired, the Arizona Supreme Court ruled Friday.

The justices rejected a claim by two individuals that the fact they have a state-issued card allowing them to ingest the drug gives them automatically means they can never be charged with driving while impaired. Chief Justice Scott Bales, writing for the unanimous court, said nothing in the 2010 voter-approved law allowing the medical use of marijuana provides such immunity.

But Bales said the mere presence of marijuana in a person’s system is not proof that someone is actually impaired.

Friday’s ruling creates is create what is called an “affirmative defense” for those charged with driving with drugs in their system.

In essence, they can still be charged with violating the law. And all prosecutors have to prove is that they did, in fact, test positive for marijuana or one of its metabolites, the chemicals caused when the drug breaks down in the body.

But Bales said defendants can escape conviction if they can prove to a court “that the concentration of marijuana or its impairing metabolite in their bodies is insufficient to cause impairment.”

The decision is a mixed bag for prosecutors.

On one hand, they praised the fact the high court did not say medical marijuana users can drive without fear of being stopped or prosecuted.

“This is a very welcome ruling in today’s culture, where the small minority of individuals who use marijuana seek to reorganize Arizona’s laws to protect their use to the detriment of the public’s safety,” said Yavapai County Attorney Sheila Polk.

But they were upset that the justices effectively voided the state law making it a crime for individuals to operate a vehicle “while there is any drug defined in (state law) or its metabolite in the person’s body.”

Maricopa County Attorney Bill Montgomery said that law is plain on its face: If a motorist tests positive for marijuana, he or she is guilty, period. He said that differs from other statutes where prosecutors have to specifically prove someone was impaired.

Bales conceded that point. And he said there apparently was a purpose behind that statute.

“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 definitely establish whether a defendant is impaired,” Bales wrote.

But he said there’s another law at play: the one voters approved in 2010 allowing those with certain medical conditions to legally possess and use marijuana. And that law spells out that a 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.”

Bales said those two statutes, read together, give medical marijuana patients the chance to argue that they cannot be convicted because they were not impaired.

Montgomery said there’s one big practical problem with that: There are no scientific studies which show at what level of marijuana in the blood someone becomes impaired.

That’s far different than laws dealing with drunk driving. Lawmakers have enacted statutes saying that someone who has a blood-alcohol concentration of 0.08 or more is presumed to be driving while intoxicated.

What that potentially leaves, said Montgomery, is having defendants themselves testify that they were not impaired.

For example, he said an individual could say he uses marijuana for back pains but still had a spasm, which is what resulted in the car jerking, which is why the officer pulled the person over in the first place.

“I’m going to declare from my personal testimony I wasn’t impaired, I drive like this all the time,” Montgomery said the testimony might go.

He pointed out that Friday’s ruling says that question of impairment is determined by the “preponderance of the evidence,” meaning whether something is more likely than not. And Montgomery said that could mean a defendant would be acquitted unless a prosecutor could find some way – he’s not sure how – to rebut the driver’s self-proclaimed claim that he or she was not impaired.

Friday’s ruling extends even farther the legal protections the state Supreme Court provided last year for marijuana users charged drugged-driving.

In that case, the justices threw out a conviction where the evidence against the driver was a specific metabolite, carboxy-THC. Justice Robert Brutinel, writing for the court, said there was no evidence that metabolite – the one that police routinely tested for – means someone was impaired.

More to the point, he said allowing that to become the test would be unfair.

“Because carboxy-THC can remain in the body for as many as 28 to 30 days after ingestion, the state’s position suggests that a medical-marijuana user could face prosecution for driving anytime nearly a month after they had legally ingested marijuana,” Brutinel wrote. “Such a prohibition would apply even when the driver had no impairing substance in his or her body.”

Polk said Friday’s ruling will have even more far-reaching implications if voters approve the initiative now being proposed for the 2016 ballot to allow the recreational use of marijuana.

With the question of what is “impaired” muddied by Friday’s ruling, Polk said one alternative would be for the Legislature to set a presumptive limit in statute on what automatically constitutes impairment, similar to the 0.08 standard for alcohol.

But she said one provision of that proposed ballot measure says that an individual cannot be penalized for any action solely based on the presence of marijuana or metabolites. Polk said that would forever bar lawmakers from setting such a standard, even if medical science could come up with a figure.

“This is a vital tool in keeping our roadways safe and discouraging impaired drivers from getting behind the wheel,” she said. “Given the rising accidents and fatalities involving marijuana in Colorado and Washington, the protections for marijuana-impaired drivers written into the proposed initiative to legalize marijuana should be highly concerning to Arizonans.”


  1. middlegroundprisonreform

    Both sides lost. The state lost because there is no presumption of impairment for the tiniest amount of THC; the defense bar lost because they have to prove that whatever amount of THC in their client’s system was not enough to cause impairment. How are juries supposed to decide on an individual basis (say, for a 200 lb. male or for a 120 lb female) if a person was impaired if they are not personally at the scene — unless juries will just always believe the cop (who will sometimes lie to assist a conviction)? This will create a mess of case law and is a monetary boon to the criminal defense bar. Someone needs to make a decision about an amount of THC that defines impairment (just as has been done for alcohol). Even though the amount is arbitrary and has been adjusted over the years to accommodate the prosecution (when it changed from .10 to .08), at least its a threshold. Too bad our Supreme Court didn’t have the guts to make a firm decision.

  2. Couldn’t agree more with “middlegroundprisonreform”. Total boon for the defense attorneys. I’m all for medical marijuana, and I enjoy a drink or two from time to time, but for people to think they are immune from their responsibility to drive safety is a big concern. I am sure someone will have to die before they weed this one out……gr

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