With legalization of marijuana initiatives taking hold across the nation, lawmakers believe they are dealing with a new major challenge. The problem, they say, is if people are allowed to smoke marijuana for medical or even recreational purposes, they will also be free to drive when under the influence of the drug.
Of course, this is not true. Impaired driving is impaired driving, regardless of whether the substance is legally consumed.
While this may seem similar to the problems relating to alcohol, the situation is not analogous. In the case of alcohol, it is relatively easy to test if someone is currently under the influence of the substance. As our BirminghamDUI defense attorneys can explain, the authorities may not always use a properly calibrated breath test machine or properly follow the protocols, to the point where the breath test results may be inadmissible, but there is at least a test for one's blood alcohol content (BAC).
On the other hand, marijuana is different from alcohol. In the case of alcohol, one ingests alcohol (ethanol), and if he or she is still under the influence, that person still has ethanol in his or bloodstream. This ethanol is detectable via a blood test or a breath test. The reason a breath test can detect alcohol is because, when someone is under the influence of alcohol, the alcohol in one's blood is added to the air being exhaled deep within an area of the lungs known as the pulmonary alveoli. This alveolar air is what is being measured for the presence of ethanol. This has nothing to do what alcohol a person just consumed, or the concept of having alcohol on one's breath.
In marijuana, it is chemical called tetrahydrocannabinol (THC) that causes the intoxicated effects or gets someone “high.” Unlike alcohol, the substance fully metabolizes into another substance (a metabolite) called delta 9-tetrahydrocannabinol. This metabolite could be evidence a person had consumed marijuana at some point in the last month, but since delta 9-tetrahydrocannabinol does not get one intoxicated, there is no way to determine one's level of intoxication during the time he or she was driving.
This concept is central to the problems with DUI arrests and DUI prosecution of people driving who test positive for marijuana as discussed in a recent article from the Bulletin. In the case of alcohol, despite the term being commonly used, it is not illegal to “drink and drive.” It is illegal to drive while intoxicated. Many people can legally have one beer with dinner and then drive home. There is not a zero tolerance law with alcohol for adults over 21, but it seems that is exactly what legislatures are trying to do across the country with marijuana.
As a technical note, it is possible to tell if some recently used marijuana. For example if some is given a drug test while they are on parole or probation in Alabama, and he or she fails the test, he or she may be given another test the following week. While the person will still have delta 9-tetrahydrocannabinol in his or her system from the previous positive test, based upon the level of 9-tetrahydrocannabinol, they can generally tell if the second week's test is positive for “new use,” as it often called by parole officers. However, these new and old use levels are nowhere near accurate enough to determine if one is currently high on marijuana.
As legal pot spreads, states battle drugged driving, August 27, 2015, The Bulletin, by Sarah Breitenbach
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