Ever since marijuana began tricking into the mainstream, legislators and law enforcement agencies have been trying to figure out a method to curb a predicted influx in stoned driving. Unlike alcohol, there is no breathalyzer currently available for police officers to see if a motorist has been driving under the influence of weed -- forcing states to impose unrealistic blood standards to prosecute high drivers.

In Colorado, the acceptable marijuana limit is five nanograms of THC per milliliter of blood. The problem, as Colorado medical marijuana patient Greg Duran pointed out during a recent episode of NPR’s “Morning Edition,” is marijuana has longevity in the human body, and depending on how a particular person is built, THC can linger in the system for days, putting any motorist who consumes legal marijuana responsibly at risk for DUI.

"It would be devastating if I lost my car. It would change everything," Duran told NPR, explaining that he uses medical marijuana regularly to treat nausea brought on by vertigo.

Despite the controversy surrounding inaccurate blood tests, Colorado police are not losing any sleep over utilizing this method to bust innocent people. Sean McAllister, who works as a criminal defense lawyer, says it is not uncommon for his office to receive five calls a week from people seeking council for a marijuana DUI charge.

"If you were talking about this concept with alcohol and told people, 'We got a test that can say if you drank in the last 24 hours and if you fail it we're going to arrest you for DUI,' we would be occupying the Capitol right now," said McAllister, who adds that stoned driving is a conundrum because no one knows how much is too much.

Colorado recently added several dozen certified, “drug recognition experts” to the ranks of state law enforcement to assist in keeping stoners off the road. State Trooper Nicholas Hazlett is one assigned to such duties, and he says his job would be easier if there was an accurate method, like the breathalyzer, in place for policing high drivers. "I wish we did, but no, we don't have a marijuana breathalyzer," Hazlett told NPR.

Interestingly, Hazlett admits that legal marijuana in Colorado has not caused a substantial increase in stoned driving. Recent sobriety checkpoints across the state indicate that alcohol remains a greater concern. The Larimer County DUI Task Force recently stopped over 1,500 vehicles, yielding in 22 arrests -- none of which was for driving under the influence of marijuana.