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Driving Under the Influence of Marijuana: The Struggle to Define a Legal Limit

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Legalizing marijuana before determining a legal standard for when someone is considered driving under the influence of marijuana has left law enforcement without the proper tools to keep impaired drivers off the road. Some might say it is a classic case of “putting the cart before the horse.” Others counter with the fact that the inability to determine a legal standard is due in large part to the lack of research and data on driving under the influence of marijuana, which, in turn, is due to the fact that until recently, legalization was limited to medicinal use. Whichever argument you choose, the fact remains that setting a legal limit for marijuana is proving to be much more difficult than for alcohol.

The Problem 

Your Denver accident attorney explains that the difficulty with defining a legal limit arises because of the ways that alcohol and tetrahyrdocannabinal (THC), the active ingredient in marijuana, metabolize. Alcohol’s relationship with the body is fairly straightforward: the more a person drinks, the higher the person’s blood-alcohol level (BAL) rises. Science has determined that regardless of an individual’s tolerance, anyone with a BAL of .08 percent is impaired to some degree in the skills necessary for driving. 

Unfortunately, the body’s relationship with marijuana is not as straightforward. THC, the ingredient in marijuana that causes a person’s “high” and impairment, leaves blood pretty quickly, but is absorbed by the brain and fatty tissues. Therefore, low levels of THC can still cause high amounts of impairment in drivers, making blood tests unreliable indicators of whether a person is truly driving under the influence or driving while impaired. On the other hand, THC can be detected in urine for days and even weeks after marijuana use, making urine tests unreliable as well.

Given such difficulty in determining what level of THC causes actual impairment while driving, your Denver accident attorney finds that it is no surprise that states have enacted laws with THC blood levels with a wide range, all the way from a low of one to a high of five nanograms per milliliter. Colorado passed a law in May establishing the legal limit of THC at five nanograms per milliliter in the bloodstream, which is the high end of the range. Critics accuse states with limits at the high end of the range of enacting laws that are tantamount to giving drivers a license to drive while high. The critics also believe that states with limits at the low end of the range will likely be convicting drivers who used marijuana weeks before a driving incident occurs. 

Looking To Others For Help 

When searching for law enforcement models to follow, the approach taken by New Zealand may be helpful. New Zealand uses subjective signs of impairment with a zero tolerance standard:  if a driver fails the field sobriety test, then and only then will any amount of THC in the driver’s blood be illegal. However, this approach would not help for liability purposes when an accident occurs and the driver is found to have THC in his or her system.

If you have been charged with a DUI or DWI due to marijuana, or if you have been in an accident involving someone with marijuana in their system, contact Jordan Levine at Levine Law today.