Why Marijuana Sobriety Tests are So Unreliable

Voters last month in California, Maine, Nevada and Massachusetts agreed to legalize marijuana for recreation, bringing the total to eight. But even those who support legalization recognize there is a possible threat to public safety on our roads. So that raises the question: How can you tell if someone is actually impaired by marijuana?

Answering this question has proven much more thorny than determining who is drunk. That has prompted some states to adopt measures that arbitrarily assign certain amounts in the blood as being an indicator of impairment. The problem is, these measures aren’t accurate. That means innocent people are being locked up and facing criminal and civil consequences when they have not done anything wrong. It could also mean that in some instances, drivers who really were impaired are getting away with it.

The problem is that in legally treating marijuana like alcohol, states have forgotten that the human body doesn’t treat the two substances the same way. Alcohol moves through the human body quickly. The effects of alcohol are based on a person’s weight and size, their metabolic rate, their food intake and how much alcohol has been consumed. Still, generally speaking, the more you drink, the more drunk you are going to be, which means the worse your driving will be. This is generally true no matter what your size or no matter how often you drink. The same is not true for those who consume marijuana because the drug stays in your system for much longer. A higher concentration of THC in one’s system is not necessarily an indicator of intoxication. Rather, it is generally an indicator that someone is a regular user of the drug, but not that they are currently under the influence. 

Right now, what we have is a reliable system to that can help determine how much someone’s blood-alcohol concentration is, which can give us a pretty good notion of how drunk they are. But there is no alternative to ascertain how impaired by marijuana someone is. And this is a problem.

The 2014 National Survey on Drug Use and Health indicated that some 10 million Americans conceded they drove while under the influence of drugs in the previous 12 months. Toxicology reports among drivers who crashed revealed marijuana was the second most-commonly detected substance in the at-fault driver’s blood (alcohol was No. 1). But the trouble is there is no real way for police to tell whether someone is actually impaired or simply a user of marijuana.

Recently, California scientists with U.C. San Diego at the Center for Medicinal Cannabis Research received a grant for nearly $2 million from the state to help study this information, gather data about time, dosage and what it actually takes to make the average person “impaired.” The goal for researchers is to develop a viable roadside sobriety test for marijuana.

It’s well-established that marijuana, like alcohol, impedes one’s ability to drive safely. It can reduce mental function and reaction times. But different strains can have different potency, which means that exact dosage might vary. For example, a person might smoke a marijuana joint, immediately get into his vehicle with high THC levels, but not be significantly impaired. Meanwhile, another driver might consume a marijuana-infused brownie and wait several hours before getting into the vehicle. The THC levels could actually be lower, but that driver is significantly more impaired.

These are the kinds of disparities that make setting limits for THC levels problematic.

Our marijuana DUI attorneys understand the many nuances of marijuana consumption and the effects on driving, and we work hard to defend our clients from a negative or unfair outcome.

The Los Angeles CANNABIS LAW Group represents growers, dispensaries, collectives, patients and those facing marijuana charges. Call us at 949-375-4734.

Additional Resources:

Why is it so hard to make a sobriety test for marijuana? Nov. 17, 2016, By Igor Grant, Director of the Center for Medical Cannabis Research, UC San Diego

More Blog Entries:

Report: Colorado Marijuana Potency Higher Than Most, Oct. 31, 2016, Marijuana DUI Lawyer Blog