Colorado Works On Setting THC Driving Limit

A new proposal could set the driving
THC threshold at 5 nanograms per milliliter of blood.

Colorado could soon establish tough new measures to crack down on those who toke and drive.

Under a proposal expected to be introduced at the Capitol early next year, the state would create a threshold for the amount of THC — the psychoactive component of marijuana — drivers could have in their blood. Anyone who is stopped and tests above that limit would be considered to be driving while stoned.

Drivers suspected of being impaired by marijuana or other drugs already have to submit to a blood test or face a suspension of their licenses. But the proposed law would set a standard at which the law would presume a driver impaired by marijuana.

"It will bring some clarity to the issue of whether you are or are not impaired under the influence of marijuana," said state Rep. Claire Levy, a Boulder Democrat who is likely to be one of the proposal's sponsors in the legislature. ". . . There isn't a bright line right now."

State law already bans driving while under the influence of drugs, but law enforcement officials say the law is vague on how they should establish a suspect is high. That — plus the concern that the state's medical-marijuana explosion could lead to more impaired driving — led members of a subgroup of the Colorado Commission on Criminal and Juvenile Justice to examine the issue, said Arapahoe County Sheriff Grayson Robinson, a commission member.

"It became clear to us that marijuana is an area that had not been given due consideration," he said.

Gauging impairment

The proposal, which the full commission endorsed last month, sets the THC threshold at 5 nanograms per milliliter of blood. Robinson said research shows that level is indicative of impairment. Anyone over the threshold would be presumed to be impaired, in the same way any driver with a blood-alcohol content over 0.08 percent is considered to be too drunk to drive.

Sean McAllister, a lawyer who serves on the commission's drug policy subgroup, said the research doesn't take into account the tolerance level of frequent users. He said he worries that the proposal could unfairly affect medical-marijuana patients, who may be able to have higher THC levels without impairment.

But, he said, he agrees something needs to be done, and he said he advises patients to wait at least four hours after using marijuana before driving.

"No responsible advocate of legalization believes that people should be driving high," McAllister said.

David Kaplan, the state's former top public defender, said he shares concerns over the 5-nanogram level and whether "there was a strong enough correlation on what impact it has on your driving behavior."

Still, Kaplan, who is the vice chairman of the commission, said he supports the process by which the commission came to its proposal.

Other states set limits

If the proposal is adopted, Colorado would not be the first state to set a maximum THC limit for drivers. A number of states have zero-tolerance policies for drivers with THC in their blood. A handful of states, including Pennsylvania, have a 5-nanogram limit for marijuana or its metabolites, according to the National Organization for the Reform of Marijuana Laws, or NORML.

Marijuana advocates and law enforcement officials often clash over how big of a problem stoned driving is.

A report last month from the National Highway Traffic and Safety Administration found that at least one in five drivers who were killed in car crashes in 2009 subsequently tested positive for drugs. THC or some other form of marijuana showed up in 1,085 of the 21,798 drivers killed. In Colorado, THC or some other form of marijuana showed up in 26 of the 312 drivers killed that year.

The commission's proposal will likely be turned into a draft bill and introduced in the legislature during the early part of next year's session, which starts in January. Because it has the backing of the commission, its sponsors are optimistic it will receive a warm reception.

State Rep. Bob Gardner, a Colorado Springs Republican who is the chairman of the House Judiciary Committee, which would likely be first to vote on the proposal, agreed.

"I think there's a lot of support for that idea," he said.