(Oliver Berg, AFP/Getty Images file)

Court: No medical marijuana immunity under Arizona DUI law

PHOENIX — The Arizona Supreme Court ruled Friday that medical marijuana cardholders don’t have immunity from prosecution under a state DUI law that prohibits drivers from having in their bodies any amount of marijuana or its chemical compound that causes impairment.

But the state high court’s unanimous decision Friday also said cardholders can try to show in court that they didn’t have enough of the marijuana compound THC in their systems to be impaired. An attorney who filed a brief for a defense lawyers group said the ruling was welcome because it overturns a lower court’s ruling that medical marijuana cardholders could be prosecuted for merely driving after using marijuana.

“Now at least they can drive,” said David Euchner, an assistant Pima County public defender.

Arizona is among 23 states that allow medical marijuana use. States are wrangling with a host of legal issues stemming from implementation of medical marijuana programs. The Michigan Supreme Court ruled in 2013 that medical marijuana users aren’t automatically breaking the law if they drive after using the drug and that police must show a driver was actually “under the influence” of marijuana to seek criminal charges.

The Arizona case decided Friday involved a state DUI law that bars any presence of marijuana or the compound that causes impairment. A different DUI law, which wasn’t part of the case on appeal, prohibits driving while impaired.

How the new ruling will be implemented in trial courts will take time to shake out, but it likely means lawyers will present expert testimony and make arguments to jurors like they do when drivers are charged under the impairment law, said John Tatz, an appellate lawyer for two defendants in the case.

Arizona’s medical marijuana law allows DUI prosecutions of cardholders but not if amounts of marijuana compounds in their systems are insufficient to cause impairment, and the Supreme Court rejected the defense’s argument that a legal protection in another DUI law on use of prescribed drugs provided blanket immunity to medical marijuana cardholders.

The justices acknowledged that there’s no commonly accepted threshold on what concentrations of the compound are sufficient to cause impairment and that their ruling places a burden on cardholders to prove in court that their systems don’t have enough of the impairment compound for them to be impaired.

But that’s fair, Chief Justice Scott Bales wrote in the opinion. “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.”

The ruling upheld the DUI convictions of Tatz’s clients in a Mesa court. While the defendants challenged whether they could be prosecuted, they “made no effort to show that the marijuana in their bodies was in an insufficient concentration to cause impairment,” Bales wrote.

W. Craig Jones, a prosecutor who represented the Mesa Prosecutor’s Office in the case, did not immediately respond to requests for comment.