If you've ever been pulled over and accused of driving while high on marijuana, you may have noticed that law enforcement relies solely on an officer's perception to determine whether you're impaired. Unlike with alcohol, there is no objective test or established legal limit for drivers who use marijuana in Colorado.
But late last month, state legislators settled on a standard for determining whether a driver is impaired by marijuana. A Senate committee passed a proposal that would give law enforcement a clear guideline for charging drivers with a marijuana DUI. Under the bill, drivers would be considered impaired if they test positive for 5 nanograms or more of THC, the active ingredient in marijuana, per milliliter of blood.
While many marijuana advocates agree that driving while high should be illegal, some object to the blood testing method to determine the level of impairment. THC is stored in the body's fat cells, and levels can build up over time in frequent pot users. The highest concentrations are present while a user is smoking marijuana and tend to fall below 5 nanograms within three hours, according to the National Highway Traffic Safety Administration.
Scientific testimony at the hearing was at times conflicting. A physician said there is disagreement about per se limits in chronic users. But a forensic toxicologist from the Colorado Department of Public Health and Environment testified that requests from law enforcement for blood THC tests are increasing, up to 10,400 last year. "Five nanograms is more than fair," she said.
Regardless of the disagreement over the exact number of nanograms, the measure would provide law enforcement officers with a scientific measurement. Currently it's up to police to determine whether a driver is impaired, and perceptions can vary wildly from one officer to another.
Some other states have already set a legal limit for marijuana. Nevada, a state that allows medicinal marijuana, and Ohio have a limit of 2 nanograms of THC per milliliter of blood. Pennsylvania's limit is 5 nanograms, but it's a state Health Department limit largely used in court, not by law enforcement. Most other states have a zero-tolerance policy for marijuana.
Implementing the measure is estimated to cost more than half a million dollars next year, which requires that it be approved by the spending committee as well as the full Senate. Until it becomes law, people who use marijuana before driving risk being arrested and prosecuted based on a fairly loose standard of what constitutes impairment.
Source: TheDenverChannel.com, "Senate Committee OKs Marijuana DUI Standard," Deb Stanley, Feb. 28, 2012