The state crime lab already tests blood samples in drunk driving and other cases for levels of THC. County attorneys and others argued it is time to use the information and set a threshold of impairment for pot just as there is with alcohol.
Kurt Sager, drug recognition expert coordinator with the Montana Highway Patrol, said DUI cases have remained steady in recent years while cases of drug-impaired driving are way up. He said the proposal bill doesn't target medical marijuana users, only those who choose to drive impaired.
Marijuana advocates countered that testing is unreliable and measures agents that don't cause intoxication but remain in the blood stream long after impairment.
"This law will make criminals out of people who are not driving impaired," said Rose Habib, who runs a cannabis testing lab for the medical marijuana industry.