Arizona court ruling upholds DUI blood test for marijuana and 'its metabolite'

PHOENIX — Motorists in Arizona can continue to be prosecuted for driving under the influence of marijuana even if the only proof is a blood test that shows a chemical compound that doesn't cause impairment but can remain in the blood for a month, a state appellate court has ruled.

The Court of Appeals ruling overturns a decision by a lower court judge who said it didn't make sense to prosecute a person with no evidence they're under the influence.

The lower court judge cited the proliferation of states easing their marijuana laws, but the Court of Appeals ruling issued Tuesday dismissed that by saying Arizona's medical marijuana law is irrelevant regarding DUI.

The Legislature adopted the decades-old comprehensive DUI law to protect public safety, so a provision on prohibited substances and their resulting chemical compounds should be interpreted broadly to include inactive compounds as well as active ones, the Court of Appeals said.

The case stems from a 2010 traffic stop in Maricopa County. The motorist's blood test revealed only a chemical compound that is found in the blood after another compound produced from ingesting marijuana breaks down.

According to testimony by a prosecution criminalist, the compound found in the man's blood doesn't impair the ability to drive but can remain detectable for four weeks.

The man's lawyer argued Arizona's DUI law bars only marijuana and "its metabolite," so only the first derivative compound that actually impairs drivers is prohibited.

Two lower court judges agreed, with one upholding the other's dismissal of the case against the motorist, Hrach Shilgevorkyan.

Superior Court Commissioner Myra Harris' ruling noted that several states have decriminalized pot, and that a growing number of states, including Arizona, have legalized medical marijuana.

"Residents of these states, particularly those geographically near Arizona, are likely to travel to Arizona," Harris said in her 2012 ruling upholding the dismissal. "It would be irrational for Arizona to prosecute a defendant for an act that might have occurred outside of Arizona several weeks earlier."

However, the Court of Appeals sided with prosecutors who appealed, saying that allowing the testing for marijuana's active compound would unduly restrict law enforcement.

The ruling said it serves the Legislature's intention to have a flat ban on driving under the influence to interpret the DUI law's reference to a prohibited substance and "its metabolite" as covering both a substance's active and inactive compounds.

Michael Alarid III, a lawyer for Shilgevorkyan, said he'll ask the Arizona Supreme Court to consider an appeal.

He added the testing issue is increasingly important because people legally using pot in two Western states — Washington and Colorado — that last year approved marijuana decriminalization laws could be convicted of DUI if arrested while driving in Arizona weeks later.