Recreational marijuana sales are heating up in Colorado. As police officers prepare for an increase in impaired drivers there, experts elsewhere are still debating the standards of what makes a driver too high to drive.
In Colorado, according to 9news, officers will administer field sobriety tests to drivers suspected of driving high. The current standard in Colorado for too high to drive is 5 nanograms of THC per milliliter of blood. Juries could convict a driver based on that number alone.
That's a problem, since the 5 ng/ml benchmark is considered unreliable by experts. Concerns over testing impaired drivers nearly killed Colorado's recreational marijuana use bill earlier this year. Experts are unsure over what constitutes impairment since pot doesn't affect drivers the way alcohol does. The highest concentrations of THC is found in the bloodstream immediately after a user smokes, but the highest level of impairment comes 20 to 40 minutes after using, when THC blood levels have actually dropped, making such blood tests less meaningful for law enforcement.
THC absorption levels vary between users. An occasional user, who might experience impairment at 5 ng/ml of THC can't compare to a heavy using cancer patient who might have such levels sustained in their blood whether they've been smoking pot that day or not and show no impairment. In fact, CNN tested drivers with five times the legal limit of THC in their blood and found drivers were actually more cautious than before partaking. Participants had to ingest a huge amount of marijuana before they showed any impairment.