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Low THC Levels Don’t Cause Car Accidents: Study Reveals

Published September 9, 2019 by ADRAS & ALTIG, Attorneys at Law
cannabis pipe

New research indicates that Nevada’s drugged driving laws may penalize drivers for marijuana use that does not have an adverse effect on driving ability.

The study from the University of British Columbia (UBC) suggests that THC levels less than 5 nanograms/ml of blood do not lead to an increased risk of causing car crashes in most drivers. Nevada’s DUI law (NRS 484C.110) holds that a driver is automatically guilty of impaired driving if found to have 2 nanograms/ml of marijuana (Delta-9-THC) or 5 nanograms/ml of marijuana metabolite (11-hydroxy-THC, i.e., metabolized THC) in their blood or urine.

The study was published in the peer-reviewed journal Addiction in May and reported by the Vancouver Sun and other mainstream publications in June.

“At blood levels of less than 5 nanograms/ml, THC does not appear to be associated with an increased risk of crashing,” Dr. Jeffrey Brubacher, associate professor in the department of emergency medicine at UBC and principal investigator for the five-year study, told Medical Xpress. “That’s significant because the new impaired driving laws do include penalties for drivers with THC levels between 2 and 5 nanograms/ml, suggesting that the laws may be too strict.”

Brubacher was speaking of Canada’s drugged driving laws, in which per se THC levels for guilt match Nevada’s.

So-called “per se laws make it illegal to drive with amounts of drugs in the body that exceed set limits. Five U.S. states have specific per se limits for THC (tetrahydrocannabinol), the active ingredient in marijuana, according to the Governors Highway Safety Association.

Brubacher and his research team point out that per se laws are particularly unfair to habitual marijuana users, because illegal THC levels remain in the body long after the impairment has worn off.

After smoking a joint, the user’s THC level is about 100 nanograms/ml for several minutes but drops very quickly to less than 2 nanograms/ml in four hours, Brubacher said. THC also accumulates in body fat and is slowly released into the blood of a user who smokes marijuana every day.

“These people can walk around with low amounts of THC for days or weeks after they last use marijuana, so it gets complicated. … They may not be impaired,” Brubacher said. “A medical marijuana user, for example, would never be allowed to drive.”

Cannabis became legal for recreational use in Canada in October 2018 and has been legal for medical use since 2001. In the U.S., 11 states including Nevada and Washington, D.C., allow recreational marijuana use. Some states allow limited use of medical marijuana under certain circumstances.

Nevada has legalized recreational marijuana use in private homes.

How the THC Level and Impaired Driving Study Was Done

For the study, researchers analyzed blood samples from 3,005 drivers who were treated at seven trauma centers in British Columbia between January 2010 and July 2016.

Accident reports were available for 2,318 of those drivers, and 1,178 were deemed responsible for the crashes and included in the final analysis.

When blood work had been done, researchers analyzed the blood for toxicology, measuring THC levels and for alcohol and 87 other substances including cocaine, methamphetamines and a list of medications.

“What we found is interesting, and that was at these lower (THC) levels there really was no increased risk of a crash,” Brubacher said.

He also said that while there may be an increased risk of causing crashes with THC levels greater than 5 nanograms/ml, only 20 of the 1,825 samples researchers tested had THC levels greater than that amount. The study report as published in Addiction concluded that there was “a statistically non‐significant increased risk of crash responsibility” in drivers with THC levels greater than 5 nanograms/ml.

How Much Marijuana Use is 5 Nanograms of THC?

If you use marijuana and plan to drive, you need to ask yourself whether you have consumed enough to register 2 nanograms/ml of fresh THC or 5 nanograms/ml of metabolized THC should you be pulled over by Las Vegas police and tested. 

The answer to the question as to how much marijuana do you have to smoke to have 5 nanograms/ml of blood or urine is pretty much unanswerable.

A reporter for Boulder Weekly in Colorado tried to find out and decided there was no way to say for sure because:

  • THC metabolizes differently than alcohol, which we know how to measure accurately.
  • THC concentrations are vastly different for each particular strain of marijuana, so the user’s height or weight won’t make much difference, as they do with alcohol.
  • The period of highest concentration of THC in the bloodstream comes immediately after consumption, but the highest level of impairment comes 20-40 minutes after smoking, and even later with edibles. 
  • Because THC blood levels drop precipitously, blood tests done after you have been pulled over, questioned, arrested and taken downtown won’t remotely indicate blood-level THC at the time you were stopped.

A July 2017 Report to Congress about Marijuana-Impaired Driving by the National Highway Traffic Safety Administration (NHTSA) reached many of the same conclusions. It stated:

“THC level in blood (or oral fluid) does not appear to be an accurate and reliable predictor of impairment from THC. Also, when low levels of THC are found in the blood, the presence of THC is not a reliable indicator of recent marijuana use.”

Contact A Nevada Defense Attorney About Marijuana-Impaired Driving Charges

If you have been charged with DUI or DUID (driving under the influence of drugs) in Nevada based on THC levels found in a blood or urine test, you should contact a criminal defense attorney as soon as possible. Given the research discussed above, it’s reasonable to question whether you were, in fact, driving while high or impaired. There’s a possibility that a lawyer can get charges dropped or can obtain a not guilty verdict at trial.

In Las Vegas and Clark County, Nevada, the reputable and respected criminal defense lawyers of Adras & Altig, Attorneys at Law, can provide you with a strong legal defense. We have more than a decade of experience successfully handling DUI and DUID cases in Clark County courts and have the reputation and respect to ensure you get a fair hearing. Contact us today for legal assistance.

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