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By Benson Varghese

Published on: August 22nd, 2017 at 11:08 AM
Last Updated: August 25th, 2020 at 3:49 PM

When most people think about Driving While Intoxicated charges, they assume it involves alcohol. But can you be arrested for DWI in Texas if you are alleged to have been high on marijuana? Yes, depending on the facts of the case. If you have been charged with driving under the influence of cannabis, a Fort Worth marijuana DWI lawyer can help. Here’s some answers to frequently asked questions about DWI-Marijuana charges in Texas.

Is marijuana an intoxicant in Texas?

Yes, under Texas law, intoxicants include:

  • Drugs;
  • Dangerous drugs;
  • Controlled substances;
  • Combination of substances;
  • Or any other substance.

THCThe major psychoactive ingredient in marijuana is delta-9 tetrahydrocannabinol, or THC. It is one of approximately 80 chemical compounds that are unique to marijuana. THC would be considered an intoxicant in Texas for purposes of a DWI. A prosecutor could bring DWI charges based on THC or THC metabolites in a person’s system. Having a prescription for marijuana or any other substance containing THC is not a defense to driving while intoxicated in Texas.

In addition to smoking marijuana or consuming edibles containing THC, there are many other ways THC can be introduced into the body, including:

  • Hash
  • Wax and Oils – Butane Hash Oil (BHO), honey oil, budder, and shatter
  • Marijuana and PCP mixtures smoked together
  • Primo – marijuana and crack smoked together

How does marijuana affect the body?

Marijuana is a central nervous system depressant. As as a result, field sobriety tests, including the one-legged stand and walk-and-turn, may give officers useful information about a person’s loss of normal use of mental or physical faculties. Similarly, the Rhomberg Balance Test – which requires a driver suspected of DWI to close their eyes, tilt their head and estimate when 30 seconds has passed – may indicate the driver’s internal clock has slowed down.

How much marijuana does it take to be considered “intoxicated” in Texas?

Marijuana Unlike alcohol, where Texas drivers are considered to be intoxicated  if they have a blood alcohol concentration of .08 or greater, there is no such concentration for THC or any other cannabinoid in Texas. In other words, there is no per se limit or law in Texas regarding marijuana intoxication. This is due to the fact that there has not been widespread testing of THC use or concentrations in the body under controlled lab conditions in the way that there has been for alcohol. Rather, prosecutors just have to prove that the driver does not have normal use of their mental or physical faculties due to alcohol, drugs or substances in their body.

Only a handful of states have implemented a per se limit for THC in the blood. Below is a list of the states that have implemented either a per se limit or a zero tolerance for driving when there is any detectable amount of THC in the driver’s system:

Zero Tolerance – Drugs and Metabolite

The following are among the states that prohibit driving if there is any detectable amount of THC or THC metabolite in the driver’s system:

  • Arizona
  • Deleware
  • Georgia
  • Indiana
  • Oklahoma
  • Pennsylvania
  • Rhode Island
  • South Dakota
  • Utah

Zero Tolerance – Drug Only

These states prohibit driving if there is any detectable amount of THC in the driver’s system:

  • Iowa
  • Michigan
  • Rhode Island
  • Wisconsin

Per Se Limits

  • Colorado 5 ng/ML (reasonable inference)
  • Illinois 5 ng/mL
  • Montana 5 ng/mL
  • Nevada 2 ng/mL
  • Ohio 2 ng/mL
  • Washington 5 ng/mL

How do Texas prosecutors prove intoxication in Driving While Intoxicated – Marijuana cases?

So how does the state prosecute DWI cases based on marijuana when there is not a set concentration that is illegal? Under Chapter 49 of the Texas Penal Code,  intoxication is defined as:

  • not having the normal use of mental or physical faculties due to alcohol, drugs, or a combination of two or more substances; or
  • having a blood alcohol concentration of .08 or more.

As you can see, the first definition of intoxication does not require a specific number or quantitative measure of a specified drug in the body. The prosecution just has to show the defendant did not have the normal use of mental faculties or normal use of physical faculties due to the introduction of marijuana (or marijuana and some other substance) into the body.

In 2017, the National Highway Traffic and Safety Administration released a report to Congress in which it agreed that “blood THC level is not a reliable indicator of impairment.”

How long can a person be intoxicated on marijuana?

Generally, the effects of marijuana are highest within 10 to 30 minutes of consumption with some effects lasting as long as 24 hours. Unlike alcohol, which is water soluble, THC is fat soluble. For this reason, THC can be released back into the blood long after the last use of marijuana. Toxicologists at the National Institute on Drug Abuse found THC in the blood above 5 ng/mL several days after the last use of marijuana in individuals who regularly used marijuana. They also found THC in the blood of some individuals for 30 days after their last use. (Source: NPR.) This is why blood results can be misleading when trying to determine if someone is driving impaired.

What are the synergistic effects of alcohol and marijuana cases?

Alcohol is also a central nervous system depressant so the combination of alcohol and marijuana can have a synergistic effect – that is, together they have a greater effect than the sum of their individual effects. That means in a criminal DWI trial in Texas involving marijuana and alcohol, the jury may receive the following instruction:

“You are further instructed that if a person by the use of drugs renders himself more susceptible to the influence of intoxicating alcohol than he otherwise would be and by reason thereof became intoxicated from the recent use of intoxicating alcohol, he is in the same position as through her intoxication was produced by the intoxicating alcohol alone.”

Can marijuana make you a better driver or a worse driver?

In 2017, the NHTSA sent a Marijuana-Impaired Driving Report to Congress. It found that marijuana-dosed drivers tended to drive below the speed limit, allowed a greater distance between themselves and the vehicles ahead of them, and took fewer risks than when they were not under the influence of marijuana. Specifically, the report indicated:

  • Marijuana alone did not result in greater departures from the lane of travel;
  • Marijuana usage resulted in reduced mean speeds in drivers;
  • Marijuana usage increased the time individuals drove below the speed limit;
  • Marijuana usage increased the following distance between vehicles.

Despite this, NHTSA concluded that subjects were likely consciously altering their driving behavior to compensate. The report stated,”Given the large variety of driving related skills that are affected by THC, especially cognitive performance and judgment, the attempt by drivers who have ingested marijuana to compensate for the effects of marijuana is not likely to mitigate the detrimental effects on driving related skills.”

What is the biggest mistake a person can make during a DWI-marijuana case?

Remember, there is no per se limit for THC the way there is for alcohol in Texas. Prosecutors must prove their case by showing a loss of normal mental or physical faculties. The number one mistake a person suspected of Driving While Intoxicated on Marijuana in Texas can make during is to agree to do field sobriety tests. While the officer may get a warrant for your blood, the blood results alone cannot show that you were intoxicated. For this reason, some states have implemented a per se limit for THC for DWI cases. However, in blood test cases where there are no field sobriety tests, THC levels may have declined to 80 to 90 percent during the two to three hours it may take an officer to get a warrant signed and blood drawn.

What mistakes do officer’s make in DWI-Marijuana cases?

Officers generally perform three standardized field sobriety tests: Horizontal Gaze Nystagmus, Walk and Turn, and One Leg Stand. A common mistake made by officers is to administer the first test incorrectly. If a person is intoxicated on marijuana alone, neither Horizontal Gaze Nystagmus nor Vertical Gaze Nystagmus should be present. If the officer indicates either or both on a marijuana-only case, that should be an immediate red-flag that the officer is not well-versed in field sobriety tests.

In some jurisdictions, officers are trained as Drug Recognition Experts. A DRE is trained to look for signs of intoxication specific to certain drugs. For instance, a DRE who encounters a person who smells of marijuana or admits the recent use of marijuana may look for lack of convergence in the eyes, clues of intoxication on the Walk and Turn and One Leg Stand, or administer the Rhomberg test where a person estimates 30 seconds with their eyes closed and head tilted back.

What is the future of Driving While Intoxicated – Marijuana?

Expect the attention on driving while intoxicated on marijuana to increase. As more states move toward legalizing marijuana, expect more states to adopt a per se limit and states to push for blood tests to be obtained as quickly as possible after an arrest.

Consult a Fort Worth Marijuana DWI Attorney

If you have been arrested for driving while under the influence of cannabis, call a Fort Worth marijuana DWI lawyer for legal assistance. We have vast experience handling all levels of DWI and drug cases and have a proven record of success. Call today for a free consultation.