The Colorado legislature is gearing up to debate where to set the limit on how much marijuana can be in a person’s system before they are considered to be driving under the influence, according to The Denver Post.
The debate is likely to include evidence from two conflicting studies, the article notes. An analysis of nine studies, published in the British Medical Journal, found driving under the influence of marijuana is associated with an increased risk of a motor vehicle crash, especially for fatal collisions. The analysis found driving under the influence of marijuana was associated with almost twice the risk of a motor vehicle crash, compared with unimpaired driving. The studies in the analysis included nearly 50,000 people.
A second study suggests marijuana-limit laws do not impact traffic fatalities.
The debate on drugged driving laws comes in the wake of Colorado’s passage of a recreational marijuana law in November. Currently it is illegal to drive while under the influence of marijuana in Colorado, but prosecutors must prove impairment in every case, the article notes.
One bill that will be considered by the legislature sets the marijuana limit at 5 nanograms of THC—the active marijuana ingredient—per milliliter of blood. Under the bill, a person with at least 5 nanograms of THC would not automatically be convicted, and could try to argue that they were not impaired, even if they hit the 5-nanogram limit.
Recent research conducted by scientists from the National Institute on Drug Abuse (NIDA) suggests the 5-nanogram standard may be too high to capture drivers impaired by marijuana. Marilyn Huestis of NIDA, who conducted a study on marijuana use and psychomotor function, says active THC quickly falls below the 5-nanogram limit within 24 hours. “The level of 5 nanograms per mil is pretty high,” she recently told the Seattle Post-Intelligencer. “We know that people are impaired at lower levels than 5, but the balancing act is trying to find a number that can reliably separate (the impaired from the not-impaired), which is almost impossible to do.”
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