All indications are the Vermont legislature is on the road toward a vote on a bill that will legalize a retail, taxable, regulated marijuana market. Governor Scott qualifies his support for such a bill, stipulating there must be a reliable roadside test — such as a saliva THC blood level test — to determine driver impairment before considering signing one into law.

Governor Scott’s own marijuana commission in 2018 recommended saliva THC testing even while pointing out it wouldn’t be especially effective […] there is no formula that can be broadly applied to equate THC levels with individual intoxication. Heavy and light users will vary significantly in the detectable amounts of THC and the effects of similar amounts of THC will vary widely among individuals. [added emphasis.] They did not support establishing a per se limit of detectable THC.

And while state law enforcement officials may be, err… salivating at the prospect of getting the green light to collect DNA samples from drivers, the Vermont ACLU has expressed its concern that tests could be misused. Even when a warrant is required, widespread gathering and storage of DNA samples present serious constitutional privacy questions.

An article on NYTimes.com should burst the balloons of Scott and others who have been fulminating against legalized marijuana on unscientific grounds.  The tests we use for measuring the presence of THC, though, do not measure the level of impairment. They measure whether someone has used marijuana recently. If we legalize the drug, and more people use it, more people will register its recent use even when they are not impaired. So it should be expected that more people involved in car crashes will test positive even if no one is driving while high.

Using a synthetic control approach, Mr. Hansen and colleagues showed that marijuana-related fatality rates did not increase more after [two states passed] legalization than what you would expect from trends and other states.

In Vermont the THC saliva test may function best only to measure how hard Phil Scott is tapping the brakes on an issue he seems reluctant to support or thinks is moving too fast.