Proving Impairment: All You Need to Know About the Marijuana DUI Test


Currently, some degree of marijuana use is legal in at least 33 states. Another 16 states have decriminalized marijuana. Across these states, specific policies regarding marijuana use vary.

Even in states where marijuana use is fully legal, though, driving under the influence of marijuana remains illegal.

This means that drivers need to understand what constitutes a marijuana DUI. What happens if you’re pulled over while driving under the influence of marijuana? Is there a marijuana DUI test? What are the penalties for driving while high?

Find answers to these questions and more in this guide.

Can You Get a DUI for Marijuana?

Most people associate DUI convictions with drunk driving. However, the definition of a DUI is actually broader.

Driving “under the influence” means that a person is incapable of operating a vehicle safely due to any drug or alcohol use. This definition includes driving under the influence of marijuana. It can even include driving under the influence of medical marijuana or other prescription drugs.

What Happens If You’re Pulled Over While Driving Under the Influence of Marijuana?

If you’re pulled over under the suspicion of drunk driving, the police will use one or more tests to prove your intoxication. Some, but not all, of these tests are also how to test for a marijuana DUI.

The standard tests for drunk driving include:

  • Field sobriety tests
  • Breathalyzer tests
  • Blood, urine, and saliva tests

Field Sobriety Tests

Field sobriety tests rely on the arresting officer’s observations and if you don’t want to lose DUI and DUI-D cases due to lack of evidence, check out for reliable video evidence of impairment.

For two of these tests, you’ll be asked to perform basic tasks of standing on one leg and walking a straight line. The third field sobriety test is called the horizontal gaze nystagmus (HGN) test. For this test, the officer will ask you to follow a slow-moving object with your eyes. As you do, the officer will watch for involuntary jerking that can indicate intoxication.

If you’re pulled over while high, these field sobriety tests and other observations remain an option for the officer at the scene. An officer might note the following signs of marijuana intoxication:

  • Erratic driving
  • Slow driving
  • Delayed motor skills
  • Impaired thinking skills
  • Bloodshot or glassy eyes
  • Slurred speech

He or she might also notice the smell of marijuana in the car or on your breath.

Breathalyzer Tests

Breathalyzer tests measure the amount of alcohol in your breath. Using this measure, they provide an estimate of the level of alcohol in your blood. Mobile breathalyzer devices are part of the standard procedure in most drunk driving stops.

In practice, they are not yet an option for marijuana DUIs, but they likely will be soon.

Recently, researchers at the University of Pittsburgh developed a prototype of a breathalyzer-like device that can detect THC, the psychoactive component in marijuana. The device looks much like a standard breathalyzer test. It can even detect THC in the breath when other intoxicating agents, like alcohol, are present.

Blood, Urine, and Saliva Tests

If you are arrested for drunk driving, implied consent laws mean that you must undergo a chemical test to determine your blood alcohol level. By measuring this level directly, blood tests produce the most accurate results.

Individuals arrested for a marijuana DUI are likewise subject to implied consent laws. Until a breathalyzer test for THC gains widespread use, DUI blood tests for marijuana are one of the main tools police have to prove intoxication. Saliva and urine tests provide additional options.

The problem with each of these tests, though, is that their results can take days. They also struggle to determine how long ago a person used marijuana.

Finally, even the most accurate tests face another hurdle. What level of marijuana in a blood test for DUI indicates intoxication?

What Constitutes Intoxication on a Marijuana DUI Test?

Across the United States, a blood alcohol level of 0.8 constitutes intoxication in drunk driving cases. Yet there is no agreed-upon standard for marijuana intoxication.

Efforts to develop such a standard continue. However, they face difficulty because THC and alcohol operate differently in the body.

Alcohol is water-soluble. As such, it saturates and remains well-distributed in the bloodstream. Thus, measuring a person’s blood alcohol level using a sample taken from the arm provides a relatively accurate measure of the degree to which alcohol is affecting the brain.

THC, in contrast, is fat-soluble. This means that it passes rather quickly from watery environments like the blood to fatty tissues like the brain. What’s more, over time, some of this residual THC can pass back into the bloodstream.

Different types of marijuana usage further complicate efforts to develop a “standard” for intoxication. Occasional users who smoke marijuana may show low THC blood levels within a short time. Occasional users of oral THC products may never have a high level of THC in the blood.

Then, there are frequent users who may build up such high concentrations of THC in their fatty tissues that blood tests will detect the compound even long after the person is high.

All of these issues leave the issue of marijuana intoxication open for debate. So where does that debate leave marijuana users?

Can You Drive a Car While Using Marijuana?

The safest option for any driver is to avoid having any psychoactive drugs in your system.

Marijuana, including medical marijuana, is a psychoactive drug. This means that driving under the influence of marijuana endangers you and others. If the prosecution can prove intoxication, a marijuana DUI also involves legal consequences. These vary across states but can include fines, jail time, and the loss of driving privileges.

If you’re facing these consequences, a marijuana DUI attorney can help.

If you’re just beginning to use marijuana, though, your best bet is to stay on the right side of the law. Fortunately, this doesn’t mean giving up the benefits of the marijuana plant.

In fact, the marijuana plant produces two key compounds. The psychoactive compound THC is one. The other is CBD, or cannabidiol.

Unlike THC, CBD is not psychoactive and does not produce a “high.” It does, though, produce a host of physical and mental benefits.

Enjoying these benefits safely and legally means choosing high-quality CBD products. CBD products grown from feminized hemp seeds meet these standards and ensure THC compliance.

Taking the High Road Means Driving with All of Your Faculties Firmly Grounded

As more states legalize marijuana and more people become aware of the plant’s benefits, the issue of marijuana DUIs will become increasingly important.

Driving under the influence of marijuana is illegal. Efforts to use marijuana DUI test results to prosecute marijuana DUI cases are complicated. However, they can be successful, producing serious legal consequences for the defendants.

Avoiding these consequences means making healthy and legal choices. As you strive to make those choices, count on our blog for the best advice.

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