British Company Developing Field Sobriety Test for Marijuana

January 30th 2016

Police have long searched for a quick and effective way to test drivers for marijuana, and last week, the British company Oxtox published a study on a new disposable test for high driving. The test's efficacy rate makes it a promising development for law enforcement and a formidable threat to avid smokers and medical marijuana patients.

It's hard to test for weed in roadside stops.

As ATTN: has reported, the laws around driving while high are often left to interpretation of local police officers. In Colorado, there is a legal THC limit of 5 ng/ml, but the law leaves room for cops to make DUI arrests on a case-by-case basis. Ohio, Montana, Nevada, Pennsylvania and Washington also have specific THC limits, but the speed at which cannabis is metabolized and tested makes the laws tricky to enforce.

"THC is a molecule that really loves human fat, and when you ingest it, it sticks in the fat, and then it slowly seeps out over the course of a week, or a month if you are a heavy user," Timothy Fong, an addiction psychiatrist at the University of California Los Angeles, told NPR.

thc moleculeWikimedia - wikimedia.org

Cannabis can't be tested reliably with a breathalyzer because of how THC is metabolized, and the blood and urine tests typically used to test those accused of marijuana impaired driving aren't especially reliable due to the variability of users' tolerance for marijuana.

"Most of the marijuana testing has been done in human laboratories, and there you get a wide variety [of reactions]," Fong said. "So if you take 100 people and have the same blood level of marijuana, you'll have 100 different reactions."

Some Colorado arrests have let to acquittal because law enforcement simply cannot prove how high you are, when you smoked, and how it effects you. This has greatly frustrated law enforcement officers in the state, so the Oxtox device may mean more marijuana DUI convictions and less cases making it to trial (most DUI cases do not make it to trial because breathalyzers are typically reliable and regarded as such).

How it works.

The Oxtox device analyzes the THC in saliva with an electrochemical current generated on a disposable screen-printed electrode.

While a breathalyzer measures blood alcohol level by monitoring ethanol in a person's breath, the Oxtox device measures THC by generating a current that reacts to THC in saliva.

The device has only a 1 percent false positive rate, but it has a 28 percent sensitivity rate, which means that it spots a smoker slightly less than a third of the time. Though this rate may not sound entirely terrifying, THC lingers in your system long after you've toked up, meaning those who smoke weed on a daily basis will always be rolling the dice when they get behind the wheel.

“I and thousands of other medical marijuana patients may be risking arrest every time we drive,” a Westword reporter wrote in a piece on the then-impending blood tests. In contrast, roadside saliva testing may pose an even greater threat.

Dr Dre Smoke Weed EverydayPinterest/KimberlyRounds - pinterest.com

Is driving stoned safe?

A February 2015 study found that stoned drivers are far less likely to crash than drunk drivers, even concluding that marijuana has no impact on driving safely.

While a blood alcohol concentration of over .05 increases the risk of car crash by almost seven times, marijuana was found to have no statistical correlation with crash risk.

Though some smokers' claims that weed improves their driving may sound a little dubious, research indicates that hitting a bowl and getting behind the wheel is not comparable to driving with "drunk goggles." Anti-drug groups and law enforcement officers do not necessarily see things this way.

"We have so many processes in our brain that help us to do a complex behavior of driving, and under the effects of marijuana, we just don't perform as well," said Marilyn Huestis, the senior investigator of a study conducted by The National Institute on Drug Abuse.

Why stoners are scared.

The inaccuracy of today's "420 DUI" arrests has created a gap in the market that drastically incentivizes developing devices for measuring marijuana intoxication.

"I think that people want to have a clear-cut, black-and-white solution," Mason Tvert, the communications director for the Marijuana Policy Project, told NPR in 2014. "They want a specific number that we can use to just say that this person is impaired or not. Unfortunately, it's a little more of a gray area than that."

Legalization has remained a contested issue since, and technological advances like the Oxtox device suggest that marijuana impaired driving won't remain a gray area for long.

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