Colorado legislators are expected to propose toking-and-driving bill

Colorado lawmakers are considering presenting a proposal to the legislature early next year that, if passed, would set a “per se” standard for persons driving under the influence of marijuana. In other words, they are looking to set a level at which a driver will automatically be presumed to be driving impaired.

The state’s driving under the influence (DUI) laws already prohibit a person from operating a vehicle while under the influence of alcohol, drugs or both.  But there are two separate DUI charges — DUI and per se DUI. The DUI law makes illegal for a person to be “substantially incapable” of safely operating a vehicle due to the consumption of alcohol or drugs.  This law does not have a blood-alcohol level requirement, and a person can be convicted of DUI without a blood-alcohol test number as evidence.

Per se DUI, on the other hand, presumes that it is a crime to drive a vehicle with a blood-alcohol content of 0.08 grams of alcohol per 100 milliliters of blood or 210 liters of breath within two hours of operating a vehicle.  A prosecutor does not have to prove that the driver was “substantially incapable” of safely operating a vehicle.

The lawmakers’ intention is to establish a similar threshold for the amount of THC (the active component of marijuana) in the blood. It is expected that they will propose a limit of 5 nanograms of THC per milliliter of blood. Anyone with a blood-THC level over 5 would be considered to be too high to drive.

Critics of the proposal contend that a per se law does not take into account people’s tolerance levels. Attorney Sean McAllister told the Denver Post he is concerned that such a law could unfairly affect medical-marijuana patients, who may have high THC levels in their blood without being impaired.

Rep. Claire Levy (D-Boulder), who sponsored tough new DUI laws that went in effect July 1, is expected to be one of the sponsors of the THC proposal.