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Lackey urges THC test targets impaired motorists


Assemblyman Tom Lackey (R-Palmdale) has expressed concern that if voters pass Proposition 64 in November, which would legalize recreational marijuana, law enforcement personnel patrolling the highways will not be equipped to detect the illegal amount of suspected THC impairment in motorists. THC (Tetrahydrocannabinol) is the mind-altering ingredient in cannabis.

Lackey, a retired California Highway Patrol officer, wants the state to adopt a legal limit for THC. Without it, he said, patrol officers must rely mostly on their own subjective judgment as to whether a motorist is high on marijuana.

“In my own experience, I’ve seen this phenomenon,” Lackey said. “I’ve seen somebody clearly impaired, and I’ve seen officers still hesitant to remove [that person] from the roadway because they’re not a drug recognition expert.”

Drug recognition experts reportedly have advance training in identifying impairment levels caused by marijuana and many other drugs. Lackey said most CHP officers don’t have this capability. He previously co-sponsored legislation—similar to drunk-driving laws—that would make it easier for officers by creating a legal blood limit for THC, but it failed last spring partly, according to experts, because THC levels are not good indicators of intoxication.

“Unlike alcohol, which has a generally linear relationship between the amount of alcohol you consume, your breath alcohol content and driving performance, the THC route of metabolism is very different,” said Tom Marcotte, co-director of the Center for Medicinal Cannabis Research at UC San Diego.

Because THC is fat soluble—unlike alcohol—it doesn’t absorb uniformly into the body’s fluids and tissues, therefore the measure of THC in one’s breath, urine or blood does not necessarily correspond to impairment in the same predictable way as alcohol.