Marijuana Users Beware


Asheville criminal lawyer James Minick

Attorney James Minick of Minick Law, P.C.

In North Carolina it is illegal to drive a vehicle while under the influence of an impairing substance. Impairing substances include alcohol, illegal drugs, prescription medications, and marijuana.


With many states passing laws that legalize marijuana, either for recreational use or medical use, or passing laws that decriminalize marijuana (make marijuana possession a crime that cannot be punishable by jail), the number of marijuana users is growing every day.


So can you be charged with DWI in NC based on marijuana? The short answer is yes, but the longer answer might be concerning to many marijuana users.


If you are driving with marijuana, not only are you likely to be charged with possession, but you have a heightened probability of being investigated for DWI if the officer believes you have recently consumed or smoked marijuana.


Investigating a Marijuana DWI: Marijuana Use = Marijuana Impairment


In North Carolina most patrol officers that charge DWI receive little if any training on drug (non-alcohol) impaired driving. For instance, in Buncombe County (Asheville, NC) where I practice, less than 5% of State and local police are drug recognition experts (DREs). While many officers are not highly trained to detect drug impairment in a suspect, the number of non-alcohol DWI charges continues to rise across the state.


So the question becomes how does an officer prove a driver is impaired by marijuana? Officers may point at any number of indicators of marijuana use:

  • The suspect had a greenish tinge on his tongue
  • The suspect told me that he had used marijuana “recently”
  • I found marijuana in the suspect’s vehicle
  • I found a pipe in the suspect’s vehicle
  • The suspect’s vehicle smelled like marijuana


While these items might be evidence of marijuana use, they do not address the issue of whether the suspect was impaired by marijuana at the time of driving.


Many patrol officers have received basic training for conducting Standardized Field Sobriety Tests in alcohol related DWI investigations. One of the tests officers receive training on is the Horizontal Gaze Nystagmus (HGN) test. This is a test used to detect alcohol impairment and certain types of drug impairment, but a person will not exhibit HGN due to marijuana impairment.


Most officers have limited training in investigating impairment by substances other than alcohol. Because of their limited training, the primary question of many drug related DWI investigations is: was the suspect using an impairing substance?


Blood Testing

In North Carolina there is no per se impairment law for marijuana (or any drug) as there is for blood alcohol impairment (.08 or more grams of alcohol per 100 milliliters of blood). So a specific amount of tetrahydrocannabinol (THC), the psychoactive compound in marijuana, or tetrahydroncannabinolic acid (THCA), THC’s non-psychoactive pre-cursor, is not relevant to a DWI charge based on marijuana impairment.


In theory the primary purpose of getting a blood test showing substances in a suspect’s blood is to verify the officer’s suspicion as to which specific impairing substances the driver has taken.


In practice many officers (and even some courts) look at the blood test as substantive evidence of impairment.


Most scientific research would not support the theory that the results of a blood sample show that a substance was consumed at a specific time, or that an individual was impaired by a substance at a specific time. In fact many chemical compounds related to illegal substance or prescription medications can remain in a person’s blood in detectable amounts for 30 days or longer.


THC can be found in heavy marijuana users for up to 30 days. What this means is that if an officer suspects that an driver who regularly used marijuana is impaired while driving and requests or compels a blood test, the results of the blood test would likely confirm marijuana use.



If you are a regularly marijuana user, you need to be aware that marijuana use puts you at a heightened risk of being charged with DWI, regardless of whether you are actually impaired at the time of driving. If you have been charged with possession of Marijuana and/or DWI, please call or email our office and we’ll be glad to speak with you about how best to handle your case.  Consultations are always free.



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