AUGUSTA — Maine State Police will ask state lawmakers to make it legal for police to test drivers who may be impaired by 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 department spokesman Stephen McCausland.

In Maine, drivers are required to submit to blood tests to determine whether their blood-alcohol content is below the legal threshold of 0.08. 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, known as THC, 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. In Washington, where recreational use is legal, the limit is 5 nanograms of THC per milliliter of blood, which some say corresponds in terms of impairment to a blood-alcohol level of 0.08.

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

McCausland said the level at which Maine’s THC blood-level limit would be set would be decided once a draft of the bill is released.

Advocates for legalizing marijuana in Maine said they have concerns about trying to treat the drug the same as alcohol and noted that a blood sample is necessary to test accurately for the presence of THC.

David Boyer, the statewide political director for the Marijuana Policy Project in Maine, said advocates for legalization agree with police that it should be illegal for people to drive when impaired or under the influence of any drug but said the state doesn’t test drivers for other substances such as 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 they last used marijuana. He said 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.

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

Meanwhile, Paul McCarrier, a former legislative liaison for the Medical Marijuana Caregivers of Maine, said there is concern marijuana patients, “could be criminalized for taking their medicine and driving.”

“Patients who have PTSD or epilepsy and use marijuana need to take their medicine so they can be safe drivers,” McCarrier said in a statement emailed to the Sun Journal.  McCarrier said there is understanding for the department’s desire to “get ahead on this issue” but also said police have existing drug-impairment recognition experts and testing for THC still remains unreliable.

“Any law that is proposed should have safe guards to ensure patients are not punished,” McCarrier added.

sthistle@sunjournal.com