How Law Enforcement Tests for Marijuana DUI

The late comedian Bill Hicks joked that driving while under the influence of marijuana was a much smaller risk for traffic safety than alcohol. Even if you do get into an accident, he quipped, so what? You were only driving 5 miles per hour!

He wasn’t far wrong, according to the National Highway Traffic Safety Administration. A Drug and Alcohol Crash Risk report from NHTSA found that “while drunken driving dramatically increased the risk of getting into an accident, there was no evidence that using marijuana heightened that risk.” And court-qualified drug recognition expert (DRE) Nick Morrow, paraphrased in Scientific American, found that “While drunk drivers tend to be over-confident, stoned drivers are the opposite… Some of them flat-out refuse to drive.”

Though the risk presented by stoned drivers may be low, law enforcement needs some way to detect and deter driving while high, maybe even get them into rehab at 12 step or non 12 step recovery programs. Even where it is has been made legal for medical or recreational purposes, some politicians, many of whom oppose marijuana legalization – such as Florida state legislators – want to aid law enforcement, even if it means using unreliable tests.

What is Driving While Stoned?

Most tests for marijuana measure levels of tetrahydrocannabinol (THC), the main psychoactive chemical in marijuana. The good news, if you’re a cannabis user stopped by the police for suspicion of DUI – is that:

  • While existing blood, urine and saliva tests can detect THC, they can’t tell if you’re high or how long ago you ingested the cannabis. The effects of smoking marijuana typically wear off after 3-4 hours – for edibles, it may be longer – but THC remains in the body for days, weeks and sometimes months.
  • Unlike alcohol, no one knows how much THC indicates you’re intoxicated. Even the AAA Foundation states, “Legal limits … for marijuana and driving are arbitrary and unsupported by science.”
  • No test akin to a breathalyzer is currently accepted as accurate by a consensus of legal or scientific authorities.

How Does Law Enforcement Test for Driving While Stoned?

Before you get sentenced to Alcoholics Anonymous, Narcotics Anonymous or non 12 step recovery programs, you have to get caught. As with drunk driving, law enforcement either sets up sobriety check lanes and checks everyone, or looks for suspicious behavior, starting with unsafe driving behavior: weaving between lanes, driving too fast or too slow, near-collisions, going through red lights or stop signs.

Once the suspect is stopped, they look for visible signs, such as red eyes, thousand-yard stares, drugs or related paraphernalia, plus the smell of marijuana. Then, police in California and other states conduct tests to determine if the driver is sober. Although none of these seem conclusive, many courts do accept their results:

  • Standard Field Sobriety Tests (SFST). There are three – the Horizontal Gaze Nystagmus Test, the Walk and Turn Test and the One Leg Stand Test – which test mental concentration and physical coordination, but there is no consensus that they they work as well for marijuana as alcohol.
  • Dräger 5000 Drug Test. This is a new saliva test being tried in Los Angeles. Police say it only tests for the “active THC compound” that indicates marijuana use in the past few hours. That’s more accurate than older saliva tests, and the Los Angeles Times says “Evidence from the Dräger 5000 will be admissible in court,” but there seems to be ample room for contention.
  • Drug Recognition Experts. DRE’s are law enforcement officers trained in how to recognize and evaluate suspects for drug impairment after their arrest. They are not considered scientific by all courts.

Reasons for Caution

Although it looks like there is plenty of room for a decent attorney to poke holes in such evidence, there’s bad news, too. For one thing, marijuana is still illegal under federal laws. Although candidate Donald Trump said he would make it easier for addicts to get into rehabs, such as non 12 step recovery programs, President Trump may instruct U.S. Attorney General Jeff Sessions to enforce those laws. In that case, any trace of THC would be evidence of guilt, and existing tests are more than capable of that.

Another reason is that new devices to test for marijuana intoxication are in development, and may be available to law enforcement as early as the end of 2017:

  • Druid tablet app. Developed by Michael Milburn, a psychology professor at the University of Massachusetts this iPad app tests reaction time, attention span and the passage of time, such as by keeping track of disappearing shapes on the screen.
  • Breathalyzers. At least two marijuana breathalyzers are in development. Cannabix says its model, using FAIMS (field asymmetric waveform ion mobility spectrometry), can detect THC in human breath, at least when the cannabis is smoked. Hound Labs says its breathalyzer also detects THC in the breath when eaten. They plan to have a model for individual use, too, so you can see if its safe for you to drive.

That is your best defense: to make sure you don’t drive drugged or otherwise impaired. Stoned drivers are better drivers than drunk drivers – Time magazine reported that in a drugged/drunk driving simulation, “While alcohol had an effect on the number of times the car left the lane and the speed of the weaving, marijuana did not” – and there are worse impairments than weed, it does have an effect. Scientific American cited a study that found the risk of crashing when stoned is twice as high as when sober, seven times as high when drunk, and 23 times as high when texting.

Besides, if you’re stopped by the police and there is any evidence that you’ve been using cannabis, you’re more likely to get arrested, whether you’re vindicated later or sent to 12 step or non 12 step recovery programs. Be smart. Get a ride from a (sober) friend, or hail a cab, a Lyft or an Uber.

BIO: Stephen Bitsoli writes about addiction and related subjects. A journalist for more than 20 years, and a lifelong avid reader, Stephen loves learning and sharing what he’s learned.

Takeaway: It’s difficult for the police to prove scientifically that you were driving while stoned, but other tests are legal, and better scientific methods are coming.

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