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National Study Suggests Blood Tests Cannot Accurately Measure Marijuana Impairment

A recent study suggests that blood tests are not an accurate method to measure whether an individual is driving while impaired by cannabis. The current legal blood levels can lead to impaired drivers going without punishment, while others are wrongfully convicted.

The study was released last month by the AAA Foundation for Traffic Safety. The AAA found that drivers can have a low amount of THC (the active ingredient in marijuana) in their blood and be impaired, while others can have higher levels and be fit to drive.

Marijuana is not metabolized in the same way as alcohol. A person with a BAC of .08 or more is considered too intoxicated to drive. However, it is not possible to say the same thing about a person with five nanograms per milliliter of blood of THC, absent additional evidence. (Five ng/ml is the level used to find impairment by Washington, Colorado, and Montana.)

The difference between the body’s metabolism of alcohol versus marijuana is significant because 12 states, including Illinois, have laws that prohibit having marijuana in the system while operating a motor vehicle. What’s more, a cannabis decriminalization bill is currently being considered in the Illinois legislature. It would raise the legal marijuana level to five ng/ml. The bill is being opposed by anti-marijuana advocates and law enforcement.

Legislators have been concerned with how to legally measure cannabis impairment as more states move to legalize marijuana, either medically or recreationally. Four states (Alaska, Colorado, Oregon, and Washington) have legalized the recreational use of marijuana. Twenty-four states, including Illinois, California, and Washington, D.C., permit medical use.

A legislative analyst for the D.C.-based policy group the Marijuana Policy Project (MPP) stated that it isn’t useful to “try to do an apples-to-apples” comparison between THC and alcohol levels in the blood. Noting AAA research, he concluded that “these things can’t really be compared.”

Additionally, THC levels have the potential to drop significantly before the administration of a test. The average time between the initial stop and a blood test is two hours, according to the AAA study. Moreover, frequent marijuana smokers can have high levels of the drug long after use, while levels decline much more quickly among infrequent smokers. It is therefore difficult to create just guidelines.

Due to issues measuring an individual’s level of impairment by THC levels in the blood, the AAA suggests looking at other indicators and using field sobriety tests. These signs include observing whether the driver has bloodshot eyes or can stand on one leg. A MADD officer indicated that field sobriety tests have proven effective in court.

A 2015 study by the National Highway Traffic Safety Administration found that there is no major accident risk associated with people driving with marijuana in their system. However, an additional AAA study suggested that fatal crashes involving drivers who had recently ingested cannabis had doubled in Washington after the state legalized the drug. That said, most drivers with THC in their systems also had alcohol or other drugs in their blood. The study further showed that drivers with THC in their systems were not necessarily at fault in the accidents.

Alcohol remains the most serious source of impairment on roads. In fact, one-third of all vehicle-related deaths are caused by alcohol.

A spokesperson for AAA Chicago said that driving with THC in the system is still a “cause for concern,” rendering it crucial to search for new ways to enforce impaired driving.

If you have been charged with a DUI crime in Illinois, it is crucial to speak to an experienced Illinois DUI lawyer as soon as possible. Harvatin Law Offices, PC provides knowledgeable representation to people in Springfield and throughout Illinois. We have considerable experience defending individuals charged with DUI offenses and representing drivers with revoked licenses before the Illinois Secretary of State. To learn more, and to set up a free initial consultation, contact us online or call us at 217.525.0520.

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