AUGUSTA, Maine — The Maine State Police will be asking lawmakers to make it legal for police to test drivers who may be impaired when using marijuana.

A bill from the Department of Public Safety is seeking to establish a limit for legally operating a motor vehicle under the influence of marijuana, similar to the state’s law against drunken driving, according to Stephen McCausland, the department’s spokesman.

In Maine, drivers are required to submit to a blood test to determine whether they are below the legal limit of 0.08 blood-alcohol level. Refusal to submit results in the automatic suspension of a driver’s license.

The department’s bill on marijuana would set a limit on the amount of tetrahydrocannabinol, or THC, the main mind-altering ingredient found in marijuana, a person could have in their bloodstream and still be considered safe to drive.

Several other states have added THC blood-level tests to their laws, including Washington state, which has a limit of 5 nanograms of THC per milliliter of blood.

Researchers in Washington also are working to establish a breath test for THC, according to a report in the News Tribune.

McCausland said the determination of what level of THC in the blood stream would constitute impaired driving in Maine would be included in bill language submitted for the Legislature’s consideration.

Advocates for legalizing marijuana in Maine voiced concerns about trying to treat the drug the same as alcohol. They also argue a blood sample is necessary to test accurately for the presence of THC.

David Boyer, Maine political director for the Marijuana Policy Project, said advocates for legalization agree with the police that it should be illegal for people to drive when impaired or under the influence of any drug. But he said a new law directed at drivers who use marijuana would be discriminatory because the state doesn’t test drivers for opiates, including methadone.

“Clearly there is still a need to develop a more refined system to determine whether a driver is impaired by marijuana,” Boyer said. “I would say opiates in this state are more of a problem than marijuana and impair an individual more than marijuana. Are the state police going to put forward a bill for that as well — to see how impaired somebody is from OxyContin?”

He said blood tests could show THC in a person’s system even three days after the person last used marijuana. Until an easy-to-administer and reliable test for THC based on good science is developed, law enforcement should remain focused on getting all impaired drivers off the road, Boyer said.

“At the heart of the issue is impairment,” Boyer said. “That should be the test and the focus.”

Scott Thistle

Scott Thistle is the State Politics Editor for the Lewiston Sun Journal. He has covered federal, state and local politics in Maine for nearly two decades.