One Year Later: Marijuana’s Impact On Nevada
……. One of the issues that remain outstanding is figuring out impairment. There is no field test for marijuana impairment. Officers are using the field sobriety test they use for alcohol impairment.
And there is still no standard for blood tests either. Someone can have trace amounts of marijuana in their bloodstream, known as metabolites, even though they are not impaired by the drug.
“It’s a challenge for us in law enforcement how we go forward and actually put a case together to show that level of impairment,” he said
https://knpr.org/knpr/2018-06/one-year-later-marijuanas-impact-nevada