The Dangers of Driving While Under the Influence of Marijuana

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Given the increased permissibility and accessibility of marijuana throughout Colorado, questions have been raised regarding the impact of marijuana use on driving performance and the risk of motor vehicle collisions.  While scientific research on this issue has gained momentum in recent years, the results are clouded by inconsistent findings and methodologies.  Some researchers believe marijuana has a minimal effect on psychomotor skills. Others have concluded drivers who tested positive for marijuana within several hours of use were more than twice as likely to be involved in a motor vehicle accident.

Unfortunately, this topic is no longer just academic in nature.  In 2013, voters in Colorado approved Amendment 64, making it legal for anyone over the age of 21 to use or possess marijuana for any purpose.  While the law did not make it legal for people to smoke pot and get behind the wheel, many users continue to do so.  The 2012 National Survey on Drug Use and Health (NSDUH) revealed an estimated 10.3 million adults (3.9 percent) reported driving under the influence of illicit drugs the year prior.  According to the National Highway Safety Administration’s (NHTSA) Fatality Analysis Reporting System (FARS) census, 3,952 fatally injured drivers tested positive for drug involvement in 2009.

It is so important that drivers use the newly legalized drug in a safe manner and understand the negative consequences associated with driving under the influence of marijuana, which include short-term memory, hand-eye coordination, concentration, and perception of time and distance. By way of example, in January of 2014, one week after the new law passed, a 23-year-old man crashed his pickup into the rear of two Colorado State Patrol cars.  A State Patrol spokeswoman said shortly after the collision that investigators suspected the driver was impaired by marijuana when the crash happened.  This incident is one example of what could be a disturbing trend: a rise in marijuana-impaired driving.

It is clear that driving under the influence of marijuana is deadly.  How though are police detecting marijuana on drivers?  To fully explain this topic, it is important to discuss the differences between reasonable suspicion and probable cause.

Defining reasonable suspicion in terms of familiar activities, it is the level of information and suspicion necessary for a police officer to stop and detain a motorist.  To effectuate a stop, an officer must have a strong suspicion a person is involved in criminal activity.  To make an arrest, however, an officer must meet the higher standard of probable cause. The officer must possess sufficiently trustworthy facts to believe a crime has been committed, thus justifying the arrest.

By way of example, when an officer has reasonable suspicion a driver is intoxicated, he can request the driver submit to a field sobriety test and/ or a BAC (breathalyzer) test.  If, during the field sobriety test, the driver sways, stumbles, and trips over his own feet, or if the driver’s BAC is above the legal limit, the officer will likely have sufficient probable cause to arrest the driver for driving under the influence of alcohol.

The same cannot be said of people who are driving under the influence of marijuana.  According to John Lewis, public information officer for the Colorado State Patrol, there are some tell-tale signs that tend to indicate an individual may have been smoking marijuana.  “Are their eyes bloodshot?  Watery?  Do they have trouble responding in a normal amount of time?  Is there an odor of marijuana or something else going on?”  Lewis said.  According to Lewis, these signs may be sufficient to establish a reasonable suspicion a person is driving under the influence of marijuana.

How, then, do police establish probable cause to make an arrest for driving under the influence of marijuana?  Under Colorado law, drivers are assumed to be impaired if blood tests show a level of THC – the active ingredient in marijuana – of 5 or more nanograms per milliliter.  According to the Supreme Court of Colorado, if an officer has probable cause to support an arrest and breathalyzer, the officer may also request the driver submit to drug testing.  If the driver refuses the blood draw, the state will suspend his license for an entire year.

Driving under the influence of marijuana is a serious safety concern.  As a personal injury attorney, I support the idea of establishing a driver’s intoxication because of its relationship on liability.  I must admit, however, I am concerned with the method of gauging intoxication.  I do not believe THC is a realistic indicator of psychomotor impairment.  Because alcohol has a high affinity for water, breathalyzers are extremely accurate.  While drinkers can wait out their BAC levels, however, THC can remain in the bloodstream for days or even weeks because marijuana is stored in fat cells.  Chronic users, therefore, may test over 5 nanograms weeks after use because of residual THC in their system, thus resulting in false positives.

Bodies process marijuana in a fundamentally different manner than alcohol.  For that reason, it seems that blood tests for marijuana are nothing more than detection tests that do not reflect the degree of impairment.  I support criminalizing driving under the influence of controlled substances generally, but there has to be a legitimate way of detecting intoxication.  Because this topic is still very new in Colorado, I do not believe there will be a straight answer for a long time.

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