Court: THC in driver's blood not enough to prove DUI

2014-04-22T10:00:00Z 2014-07-13T15:50:02Z Court: THC in driver's blood not enough to prove DUIBy Howard Fischer Capitol Media Services Arizona Daily Star

PHOENIX — Arizonans who smoke marijuana can't be charged with driving while impaired absent actual evidence they are affected by the drug, the Arizona Supreme Court ruled this morning.

The justices rejected arguments by the Maricopa County Attorney's Office that a motorist whose blood contains the slight amount of a metabolite of marijuana, can be presumed to be driving while impaired and therefore driving illegally. They said the medical evidence shows that's not to be the case.

Today's ruling most immediately affects the more than 40,000 Arizonans who are legal medical marijuana users. It means they will not be effectively banned from driving, giving how long the metabolite, Carboxy-THC, remains in the blood. It also provides protection against impaired driving charges for anyone else who drives and has used marijuana in the last 30 days, including those who might be visiting from Washington or Colorado, where recreational use of the drug is legal.

The case before the court involves a driver cited for a traffic violation who, when given a blood test, was found to have Carboxy-THC in his system and was charged with driving with an illegal drug or its metabolite in his body.

A trial judge threw out the charge. But the Court of Appeals said the laws on impaired driving "must be interpreted broadly."

In arguments to the court, Susan Luder, a deputy Maricopa County attorney, acknowledged that Carboxy-THC, a secondary metabolite of marijuana, can show up in blood tests for a month after someone has used the drug. And she did not dispute the concession of her own expert witness that the presence of that metabolite does not indicate someone is impaired.

But Luder told the justices the Legislature is legally entitled to declare that a positive blood test for Carboxy-THC can be used to prosecute someone who, if convicted, can lose a driver's license for a year.

But Justice Robert Brutinel, writing the majority ruling, said that argument makes no sense.

"This interpretation would create criminal liability regardless of how long the metabolite remains in the driver's system or whether it has any impairing effect," he wrote. Brutinel pointed out that Lunder admitted to the justices that, the way Arizona law is worded, "if a metabolite could be detected five years after ingesting a proscribed drug, a driver who tested positive for trace elements of a non-impairing substance could be prosecuted."

And Brutinel noted that even prosecutors contend the metabolite itself does not cause impairment.

Copyright 2014 Arizona Daily Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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