Marijuana-impaired drivers fly under the radar


Police are adept at arresting drunk drivers, but they are coming up short on testing drivers arrested on suspicion of driving under the influence of marijuana. Law enforcement has a problem, and it begins with “THC.”

Testing for THC in drivers

For frequent users of marijuana, tetrahydrocannabinol (TCH) remains in the body for up to 10 days following ingestion. This is bad news for anyone urine-tested for a job. However, THC levels dissipate quickly. The man pulled over for sluggish driving? His eyes look like a cartoon, his car gives off enough reek to kill a drug-sniffing canine, and he’s eating the upholstery. But when he is booked and drug-tested a few hours later, he tests below the legal limit for impairment. Scientists duplicated the scenario in a lab.

Legislators in Colorado believed they came up with the solution in advance of legalizing marijuana for adults (in small amounts) in 2014. Lawmakers passed a bill making five nanograms the legal limit. This means a person pulled over or stopped on the street can be arrested for being under the influence if a blood test reveals he or she has five or more nanograms of THC in the bloodstream. Legislators in Washington set the same limit in their state.

But nothing is that easy. Officers do not conduct blood tests in the field. By the time they bring a suspect in for booking, the window may have closed to get an accurate THC reading. Australia found a workaround by deploying saliva tests in the field. But police down under admit the test has limitations. Field test results alone are not admissible in court. Australian courts only accept results confirmed by a lab.

The effect of legalized marijuana on traffic safety

The Colorado State Patrol issued a total of 5,546 citations for driving under the influence of alcohol or drugs in 2014. Over 12 percent (354) of those citations involved driving under the influence of marijuana. Marijuana was the lone substance in over 6 percent of these arrests.

The Colorado Department of Transportation maintains statistics on drugged drivers involved in fatal crashes. Again, looking at 2014 (the year when marijuana was legalized for adults), there were 488 fatalities. Obviously, any number is too high. But in the 12-year period beginning in 2003, the average fatality count was just under 530. One might expect the fatality count to be higher now that marijuana is legal. And, to some extent, this is the case. For the years 2009 to 2014, 488 fatalities was the highest annual total, but only to a very minor degree.

Washington State legalized marijuana for adults the same year as Colorado. The Washington Traffic Safety Commission’s statistics on marijuana-impaired drivers provide more conclusive proof that a correlation between legalized marijuana and auto fatalities exists. According to the Commission, the number of drivers in fatal accidents and under the influence increased 48 percent from 2013 to 2014. The largest increase in arrests was in the male, 21 to 25 age bracket.

Washington’s response

Washington State Police turned to Hound Labs, Inc. for superior field testing capability. The Hound prototype is a handheld device that measures the presence of THC. What separates Hound’s unit from the rest of the pack is it can measure THC in picograms – one trillionth of a gram. In theory, the Hound can determine with accuracy the level of a person’s marijuana intoxication at the time of arrest. The company is testing the unit now in San Francisco, but the results are not yet in.

Authorities admit legalization has opened a new area for law enforcement. Police are looking for ways to make arrests stick, and courts are figuring out how to adjudicate cases involving individuals who have the legal right to get high.

Even legal drugs have the potential to disrupt the development of adolescent minds. White River Academy’s substance abuse program focuses on treating the entire patient. We examine the underlying causes that fuel compulsive behavior. Call our 24/7 helpline for more information.

About the author:

Darren Fraser worked two and half years as reporter and researcher for The Yomiuri Shimbun until they realized he did not read, speak or write Japanese and fired him. Undeterred, he channels his love of research into unearthing stories that provide hope to those dealing with addiction and mental illness. Darren loves the Montreal Canadiens hockey club and horror films and would prefer to enjoy these from the comforts of his family’s farm in Quebec. 

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