Studies Debunk Cannabis DUI Testing Methods

s cannabis
is being legalized for recreational and medical purposes throughout the country,
there is growing concern over the impairment caused by the use of cannabis, particularly
when driving. Determining someone’s level of impairment based on blood or urine
tests to detect THC is a burgeoning science. Scientists state that the effects
of cannabis on performance is a complex issue and both a user’s history of cannabis
use and how recently they consumed cannabis are major facts that need to be
considered when determining whether there is an impairment.

We all
know someone who has been pulled over for a DUI. Police officers will ask you
to pass a field sobriety test: Follow a pen with your eyes, get out of the car
and walk in a straight line, stand on one leg for 30 seconds. Standard field
sobriety tests have been shown to catch approximately 88 percent of drivers
under the influence of alcohol. However, this test is not good at identifying a
driver who might be under the influence of cannabis.

In a
2012 study published in the Journal of Psychopharmacology, only 30 percent of
people under the influence of THC failed the field test. The test’s ability to
identify a driver impaired by cannabis relies heavily on whether the driver is
accustomed to consuming cannabis. Distinctions like this are growing more and
more important for scientists. Marilyn Huesist, a senior investigator at the
National Institute on Drug Abuse says, “Our goal is put out the science and
have it used for evidence-based drug policy.” Dr. Huetiss wants to make it very
clear that cannabis use causes deficits that affect driving ability. She noted
that several researchers, working independently of one another, have come up
with the same estimate: A twofold increase in the risk of an accident if there
is any measurable amount of THC in the bloodstream. By contrast, a recent study
of federal crash data by author Eduardo Romano, found that a 20-year-old who drives
with a B.A.C. of .08 percent had an almost 20-fold increase in the risk of
fatal accident when compared to sober drives. Romano states that, “Despite our
results, I still think that marijuana contributes to crash risk, only that its
contribution is not as important.”

As scientists
continue to research cannabis’ impact on functionality, the legal system is
left waiting for clarity. There is a great deal of debate about how to best
prove that drivers under the influence of THC are too intoxicated to drive. Currently,
there is no reliable roadside test like a breathlyzer for cannabis. THC levels
have to be measured from blood or urine samples. Urine tests look for a
metabolite of THC rather than the drug itself and can return positive result
days or weeks after someone has actually consumed cannabis long after any
psychoactive effects have worn off. At this time, it’s simply unclear what
blood level of THC constitutes actual impairment.

Despite
the lack of clarity and uncertainty in the science, people still get arrested
every day under California Vehicle Code 23152(e), driving under the influence
of the herb. In California, the law does not specify the particular amount of
THC in the bloodstream that automatically establishes impairment.

San
Diego criminal defense attorney Melissa Bobrow explains that to be found guilty
of a DUI cannabis, the prosecutor must prove: 1) You drove a motor vehicle, 2)
under the influence of cannabis, and 3) because of the herb, your mental
abilities were so impaired that you were unable to drive with the caution of a
sober person, using ordinary care, under similar circumstances. Melissa notes
that a chemical test result is NOT necessary to convict of DUI cannabis. It’s
just one piece of evidence used to show you drove impaired. So even if you
refuse to take a chemical test, you can still be charged under Vehicle Code
23152(e). In addition to a chemical test, evidence of DUI cannabis can include
your driving pattern, statements to police, physical appearance, and presence
of cannabis or paraphernalia in your car or on your person.