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By Brian Bakst, Minnesota Public Radio News

It was a footnote in an easy-to-miss Minnesota Court of Appeals decision in December of 2020, a ruling that overturned a man’s DWI conviction involving marijuana use.

“Unlike alcohol, there is no statutory threshold for the amount of THC at which a person is considered ‘under the influence,’” the footnote in a decision written by Judge Lucinda Jesson began, adding that the mere presence in the Cottonwood County defendant’s blood “does not necessarily prove that his driving was influenced by the substance.”

The ruling itself was unpublished, which reduces its standing as precedent in similar cases. But as marijuana switches to a legal substance next week, it’s the kind of dispute that is sure to gain more attention as defendants, lawyers and judges work to sort out the new landscape.

Ahead of the change, prosecutors and police chiefs are actively discussing practices around stops and vehicle searches. Defense attorneys also have their eyes open for ways to test the shifted boundaries.

There are surprisingly few cases in Minnesota where the state’s appellate courts have weighed in around strictly marijuana-related driving offenses.

In the 2020 case, the man had been at a park in the early morning hours and police stopped his vehicle as he left. The officer observed bloodshot eyes and the faint smell of what he believed was alcohol and marijuana. But a preliminary breath test didn’t detect alcohol.

A passenger in the car was arrested on a probation violation and the driver went to the jail to pick him up. While there, the officer did more tests on the driver, arrested him on suspicion of DWI and collected a blood sample that later indicated active marijuana chemical THC was present.

After his conviction, the man appealed and the higher court found that lack of proof of erratic driving or observed traffic violations was grounds for reversal.

“In other words, if we test somebody’s blood and they have THC in their system, we don’t know when they smoked and we don’t know if they’re actually under the influence,” his attorney, Veronica Surges, said in a recent interview. “What matters is whether you are fit to drive.”

Minnesota law enforcement officials and prosecutors said the distinction between suspected alcohol and drug-related driving arrests isn’t new to them. But they acknowledge they’ll have to clearly document bad driving conduct and findings of impairment exams to make cases stick as they expect to encounter more of them.

“For alcohol, we have a 0.08 standard. There isn’t a quantitative threshold like that for marijuana where it’s going to be against the law per se,” said Bill Lemons, the traffic safety resource prosecutor for the Minnesota County Attorneys Association. “We’re going to have to prove that they were impaired by the marijuana.”

He said the more stops of suspected marijuana-impaired driving where a drug recognition evaluator is brought in the better.

An oral fluid test for marijuana is in the works, with a pilot project running for a year starting in September. Blood and urine tests are an option now, although the results are far from instant.

Those too might invite legal challenges.

“As we develop the technology to determine whether somebody is actually under the influence by a blood test, I think there’s going to be a lot of litigation surrounding that determine whether it’s accurate technology, whether that individual person was under the influence as based on the level of THC in their blood,” Surges said.

Legal experts are also bracing for tussles over open-package provisions in the new marijuana law as well as when full-scale searches of vehicles are legally justified.

“The Legislature has created some new things within the marijuana bill itself that will have to be interpreted by the Court of Appeals. There’s some open questions,” said Justin Collins, an assistant Washington County attorney who is assigned to that area’s drug task force.

Collins has been conducting training sessions with area law enforcement and others around how to approach legal marijuana.

“I would expect that every marijuana case we charge going forward will be challenged in some way if the drugs were obtained via a vehicle search,” he said.

Lemons agrees.

“Within Fourth Amendment searches and seizure, I would anticipate the Fourth Amendment issues would probably be heavily litigated pertaining to marijuana,” he said.

Before, just the scent of marijuana or open display of paraphernalia could be enough to touch off a search. Now it might come down to whether an officer smells burnt marijuana — signifying potential active use. Or if they see raw marijuana out in the open.

A case argued before the Minnesota Supreme Court in April deals with whether the odor of burnt marijuana is sufficient cause for a search without a warrant. A decision is pending.

Things might be especially tricky prior to the launch of a retail market. The open-package clause contemplates cannabis products sold in sealed packaging. Cannabis shops might not open until 2025, but people can grow their own this August.

Colonel Matt Langer, head of the Minnesota State Patrol, said people need to be aware of both the cap of two ounces of possession in public and how they’re moving it around.

“If you’re growing it at home and just transporting it in ziplock baggies, which would be legal under a certain amount come August 1, you got to pay attention to the open-container law because the only way that you can transport that as if it’s in the farthest point away from you,” Langer said. “Keep it simple. It’s just like a 12-ounce can of beer; if it’s cracked open, you can’t have it in your console.”

In other words, have it in the trunk, not the glove compartment.

Around all of these issues, the first cases to reach the state’s appellate courts will set the tone for years to come. Judging by what’s happened elsewhere upon legalization, the volume of cases could jump.

“I don’t think most states are necessarily prepared for what kind of challenges might be out there when it comes to marijuana use, which is why you see lots of inconsistency from one state to another as it relates to case law,” said Mark Stodola, who tracks the issue extensively for the Association of Probation and Parole Officers. “So could Minnesota experience this? Absolutely, I can’t tell you that they will. But I can tell you that in other states, that has certainly been the case.”