New Device To Detect Drivers’ Marijuana Use Could Lead To Undue Punishment Of Patients

Photo by Soru Epotok.


by Aaron Kase

on April 27, 2015

Police could soon be getting a new tool to bust people for driving while high — and maybe violate their civil liberties while they’re at it.

Students at the University of Akron claim that they have invented a device called the Cannibuster that can measure the marijuana levels in someone’s blood based on a field test of their saliva. Biomedical engineering graduate students Mariam Crow and Kathleen Stitzlein received a $10,000 inventor’s award for their work on the testing sensor.

With marijuana now legal in four states plus Washington, D.C., officials are grappling with how to enforce laws on driving while impaired. Currently, there is no way to determine how stoned a driver is. The best estimate involves measuring the amount of tetrahydrocannabinol, or THC, in the bloodstream, but that requires a blood test and a lengthy wait.

The Cannibuster promises to do away with the delay and allow police to instantaneously discover if people are driving with THC levels above the legal limit.

“Today if a driver is suspected of impaired driving due to marijuana, law enforcement officers must call an Emergency Medical Squad to the scene or take the driver to a local hospital for blood work,” the students said in a press release. “Lab results can take up to six weeks to come back, which is clearly not ideal.”

However, there are a number of caveats about THC-testing devices that should put the brakes on efforts to distribute them to officers in states where marijuana is legal.

For one thing, field breathalyzers for alcohol are known to be faulty and inaccurate themselves. Whether the Cannibuster or similar devices are any more reliable is yet to be seen.

Furthermore, the THC blood level is not necessarily an accurate indicator of how high a person is after smoking or otherwise ingesting marijuana. Different people have different levels of tolerance, and tolerance to higher THC levels increases with sustained use. Often medical marijuana patients who use concentrated doses of cannabis to treat illnesses daily have unusually high tolerance levels and will not be experiencing psychoactive effects even though their THC levels might be above the legal limits. Additionally, traces of the chemical can remain in the body for days or weeks, potentially putting drivers at risk for a DUI even if they haven’t smoked all day and aren’t under the influence at all.

Washington state and Colorado have set legal driving limits at 5 nanograms of THC per milliliter of blood, and other states could follow suit, but that number is effectively plucked out of thin air.

“We don’t have a consensus as to what levels of THC are consistently correlated with behavioral impairment,” Paul Armentano, deputy director for NORML, said to Business Insider. But, he added, “Marijuana policy has never been driven by science in this country.”

Finally, evidence does not support the notion that driving while high is all that hazardous to begin with, at least compared to driving drunk. Driving a car is one of the most dangerous activities most Americans do, and anything that diminishes a driver’s performance, be it from alcohol, marijuana, fatigue, cell phone distraction or other impairment, only adds to the risk. However, according to a study released by the National Highway Traffic Safety Administration this year, drivers were no more likely to crash after smoking pot than drivers not under the influence. Drunk drivers, meanwhile, were nearly 600 percent more likely to be involved in an accident. Past studies have found similar results.

Marijuana can affect peripheral vision, balance, concentration and reaction time, so it’s never a good idea to take a car on the road when you aren’t operating at peak capacity. But that doesn’t mean that a field saliva test will be an accurate barometer of who is and isn’t safe to drive.

The National Highway Traffic Safety Administration (NHTSA) states it clearly:

“At the current time, specific drug concentration levels cannot be reliably equated with a specific degree of driver impairment.”

Nevertheless, law enforcement could soon be locking up sober drivers based on an arbitrary and meaningless benchmark.