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SJC looks at marijuana sobriety tests for drivers

A man smoked marijuana. Hilary Swift/The New York Times

In a state that just legalized the recreational use of marijuana, can field sobriety tests used to determine whether drivers are drunk also be administered to demonstrate that a person is too high to operate a motor vehicle?

The state Supreme Judicial Court on Friday took up that question in a case that is being closely watched by police and advocates for marijuana legalization.

The justices also heard arguments over whether police officers can give jurors their opinion of whether a driver is drugged on marijuana.

The debate comes in the case of Thomas Gerhardt, 25, who is fighting charges of operating under the influence of marijuana. The court took the matter under advisement and will issue its decision later.


Gerhardt’s lawyer said there is no scientific evidence correlating a driver’s performance on field sobriety tests and impaired driving in cases where marijuana use is suspected.

“The point here is that in alcohol cases they have shown a correlation,” attorney Rebecca A. Jacobstein said. “But there is nothing in that for marijuana.”

Lawyer Michelle R. King, who represents Worcester District Attorney Joseph D. Early Jr., disagreed, arguing that jurors should be allowed to hear about field sobriety testing when a driver is accused of driving high.

She said three recent studies have shown connections between poor performance in field sobriety tests and some level of tetrahydrocannabinol in the blood. Tetrahydrocannabinol is the main psychoactive ingredient in marijuana.

“The police officer may then testify, as they do in alcohol-related impairment cases, that these were my observations when the driver performed the field sobriety tests and it is my opinion that the driver’s driving abilities were diminished,” King said.

Gerhardt was charged after being pulled over at about 12:20 a.m. on Feb. 13, 2013 in Millbury, court papers show. A State Police trooper stopped Gerhardt because he was driving with his vehicle’s rear lights off, the papers said.


The trooper detected the odor of burnt marijuana inside the vehicle, and Gerhardt acknowledged there were “a couple of roaches” in the ashtray, according to the papers.

He later told the trooper that he had smoked about a gram of marijuana three hours beforehand, the court records show.

During the stop, Gerhardt performed field sobriety tests. He successfully recited the alphabet, and counted numbers backward. He showed no signs of involuntary jerking or bouncing in the eyes when asked to follow a slow moving object like a pen or flashlight horizontally, symptoms that officers look for during roadside tests, court papers said.

But Gerhardt performed poorly when asked to stand on one leg and take nine steps in a straight line and turn, leading the trooper to conclude that he was impaired and under the influence of marijuana, court papers said.

During a search of Gerhardt’s vehicle, police said they found roaches and a marijuana stem.

Jacobstein argued that a police officer’s assessment of whether a driver safely operated a motor vehicle cannot stand alone when marijuana use is suspected.

Jurors need to hear from experts on this issue, she said, because the average person isn’t familiar with the physical manifestations of marijuana use and how it impacts driving ability.

“It’s not particularly helpful to the jury to hear that the officer thinks that he’s high,” Jacobstein said. “If they don’t have a general understanding of what the physical characteristics of being high are and how that correlates to driving, then all they’re doing is they’re just speculating as to what that means.”


King said expert testimony is unnecessary because marijuana use is so widespread.

“It is a common experience of a juror that an expert is not required to explain,” she said.

Justice Geraldine S. Hines asked how police could testify about field sobriety tests when scientists have not reached a consensus on their reliability despite new studies that found they can show impaired driving when marijuana use is involved.

“The 2016 studies that you are talking about would just add to the mix of different opinions about this,” she said. “It wouldn’t be dispositive or conclusive.”

Gerhardt has support from the National Organization for the Reform of Marijuana Laws or NORML and the National College for DUI Defense, Inc.

Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi.