Lawmakers remain divided over a bill that seeks to establish a blood level limit to determine whether a driver is impaired from marijuana use.

The Legislature’s Criminal Justice and Public Safety Committee voted 7-4 Thursday in favor of rejecting the bill after voicing concerns that setting a legal limit for THC, the psychoactive compound in marijuana, would not be an accurate measure of impairment because the drug affects people differently and it lingers in the blood long after its psychoactive effects have disappeared.

A minority of the committee believes the state needs to establish testing protocols to ensure police and prosecutors are equipped to handle what a recent survey by the National Highway Traffic Safety Administration found was a marked increase in the percentage of drivers testing positive for marijuana.

The debate reflects policy discussions in other states as they grapple with efforts to legalize recreational or medicinal use of marijuana. Maine already has a medical marijuana law. A bid to legalize recreational use could appear before voters in November, pending a decision by a Superior Court justice on whether supporters submitted enough valid signatures to qualify for a ballot question.

The committee vote was the second on the proposal, L.D. 1628. The committee voted 8-5 Tuesday against the bill, but brought it back as lawmakers sought to amend it. Further efforts to alter the bill sputtered Thursday after several lawmakers made it clear that they couldn’t support it.

Rep. Charlotte Warren, D-Hallowell, said the science on THC blood testing is unclear and she was reluctant to pass a bill that could ensnare people in the criminal justice system when they are legally allowed to use the drug.

Rep. James Davitt, D-Hampden, agreed.

“We’re trying to make a scientific determination and none of us on this committee is equipped to do that,” he said. “We can’t do it.”

A number of laboratory studies have determined that marijuana degrades one’s driving ability. However, research on whether it plays a role in accidents has been mixed.

According to the National Conference of State Legislatures, 17 states have laws setting limits on THC in the bloodstream while operating a vehicle. Several of those states have set the amount between 1 to 5 nanograms per milliliter. L.D. 1628 sought to impose a 5 nanogram limit – the same as in Colorado and Washington, where recreational marijuana use is legal.

Some supporters of the bill agreed to strip the 5-nanogram threshold in order to establish testing protocols, but that effort fell short.

Police already test for alcohol after fatal crashes and request testing for the presence of drugs.

Barring any further reconsideration by the committee, the bill will go to the House and Senate.

Staff Writer Steve Mistler can be contacted at 620-7016 or at:

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Twitter: @stevemistler