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Is there a roadside test that can show marijuana impairment?

On Behalf of | Dec 7, 2021 | Criminal Defense |

Not yet. There are oral fluid tests that can determine if a person has used marijuana within the last few hours, but those tests are not capable of determining whether the person is actually impaired.

However, you should not assume this means you won’t get a DWI if you’re caught driving with marijuana in your system. This is because North Carolina doesn’t allow driving by anyone with any amount of a Schedule I drug in their system, and marijuana is currently a Schedule VI drug under the federal and North Carolina Controlled Substances Acts. North Carolina law allows police to arrest a driver for driving while impaired if the officer suspects that the person is “appreciably impaired” by a controlled substance. This means that their mental and physical faculties are impaired to the point where they cannot safely operate a vehicle. Appreciable impairment is a judgment call made by the officer at the scene and can be challenged later in court.

Why can’t oral fluid tests identify impairment?

The reason these tests are incapable of showing a person is impaired by marijuana is that there is no good science saying how much of marijuana’s psychoactive substance, THC, is required for someone to be high.

Even in states where marijuana is legal for medicinal or recreational purposes, it is still illegal to drive while high. Driving while high is dangerous. Marijuana affects many important abilities that you use when driving. It can dangerously increase your reaction time, for example, or cause you to be inattentive.

The problem with enforcing these drugged-driving laws is that THC breaks down relatively quickly. That makes determining how much THC is present in the blood somewhat problematic. Police officers generally need warrants before they can order your blood drawn, and that process takes time. Then, the testing process takes additional time. With THC breaking down quickly, the amount that would have been found in a fresh blood sample might well have broken down after a couple of hours.

With that problem unresolved, many states have turned to oral fluid tests instead. Law enforcement generally does not need a warrant before requesting an oral fluid test. However, these tests can only give a yes or no answer: Did the driver have any marijuana in their system?

If the answer is yes, you can be arrested and charged with DWI regardless of whether you were actually impaired at the time.

What to do if you are arrested

If you have been arrested for DWI because you had marijuana in your system, there could be a workable defense in your case based on whether the officer was reasonable in their belief that you were appreciably impaired.

Talk to an experienced, compassionate attorney who won’t judge you but will go the extra mile to bring about a positive resolution of your case.


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