Most people think of alcohol when they think about Driving While Intoxicated, but can you be convicted of DWI 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 could help.

Is marijuana an intoxicant in Texas?

Under the broad definition above, intoxicants include:

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

THCThe active ingredient in marijuana is generally considered to be delta-9 tetrahydrocannabinol or THC. It is one of approximately 80 chemical compounds that are unique to marijuana. This could be considered a drug or “any other substance” and 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 of 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 is 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, the One Leg Stand and Walk and Turn tests may give officers useful information about a person’s loss of normal use of mental or physical faculties. Similarly, a Rhomberg test may show that the person’s internal clock has slowed down.

Synergistic effects in driving while intoxicated – 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.”

How much marijuana does it take to be intoxicated?

Marijuana Unlike alcohol that has a specific concentration where all people are considered intoxicated in Texas (.08 or greater), there is no such concentration of THC or any other cannabinoid in Texas. 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. 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

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

  • Arizona
  • Deleware
  • Georgia
  • Indiana
  • Minnesota
  • Pennsylvania
  • 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

No Tolerance under 21

These states prohibit driving if there is any detectable amount of THC in the driver’s system if the driver is under 21:

  • North Carolina
  • South Dakota

Per Se Limits

  • Nevada 2 ng/mL
  • Ohio 2 ng/mL
  • Montana 5 ng/mL
  • Washington 5 ng/mL

DWI Marijuana

Proving Intoxication in Driving While Intoxicated – Marijuana Cases

So how does the state prosecute DWIs based on marijuana when there is not set concentration that is illegal? Remember, under Chapter 49 of the Penal Code,  the first definition of intoxication does not require a specific number – the prosecution would have 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.

Even the National Highway Traffic and Safety Administration agrees that “blood THC level is not a reliable indicator of impairment.” Similarly, Tara Lovestead, a chemical engineer at the National Institute of Standards and Technology (NIST) put it this way: “There’s no quantitative measure [for impairment based on marijuana] that could stand up in a court of law.”

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 usage 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.)

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

The report NHTSA sent to Congress in July 2017 indicates:

  • 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 concludes: “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 that there is no per se limit for THC the way there is for alcohol. Prosecutors must prove their case by showing a loss of normal mental or physical faculties. The number one mistake that a person suspected of Driving While Intoxicated on Marijuana in Texas can make during the  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, states are beginning to implement a per se limit for THC for DWI cases. Further complicating matters for the prosecution in a blood test case where there are no field sobriety tests is that within the two to three hours it may take to get a warrant signed and blood drawn, THC levels may have declined by 80 to 90 percent.

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

Officers generally perform three standardized field sobriety tests: The 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?

NHTSA just sent a report to Congress on Marijuana Impaired Driving. Expect the attention on driving while intoxicated on marijuana to increase. 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.