Just like there is a law that dictates the legal limit in each U.S. with regard to blood alcohol level, there is also a law that regulates driving under the influence of drugs (DUID). When the drug is marijuana, however, passing and enforcing that law can be difficult in certain states. In Colorado, example, where recreational use of marijuana is legal, the bill dictating that driving-impaired meant a person has 5 nanograms of THC per milliliter of blood failed to get passed at least five times before it finally passed.
There are many reasons DUID laws for marijuana are controversial, and those will be discussed later. First, what is a DUID? It is the equivalent of a DUI, which means a person suspected of a DUID will be arrested and go directly to jail. However, actually being convicted of a marijuana DUID is not as cut and dry for the prosecution as a DUI is. The ease or difficulty of being prosecuted and convicted for a DUID depends upon which state the offense occurred.
Each state has one of three types of DUID laws on their books. Most states have what is called an “effect based” law. Prosecutors who are trying to show that someone has violated this law rely on evidence from law enforcement officers, a Drug Recognition Expert’s testimony, and/or a positive result on a toxicological exam. Law enforcement officers’ evidence includes such elements as performance on a field sobriety test or proof of driving at an excessive speed. A Drug Recognition Expert is a specially trained police officer who follows specific guidelines in determining whether or not a motorist is impaired by drugs. A toxicological exam for marijuana is a blood or urine test.
The effect-based approach focuses on the totality of the circumstances. Effect-based laws strike a balance in that defendants are allowed to present evidence that says, in effect, that despite their THC levels being above the legal level, they were not too impaired to drive. Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws (NORML), says this about effect-based law: “I think certainly for the consumer, this is better law than a per se law, because it allows the defendant a chance to offer evidence of their innocence at trial.”
Armentano mentions another type of DUID law, the per se law. Per se laws define a strict cut-off level of a drug metabolite or active drug constituent. Anything above that is considered as a “positive” for that specific drug, and the those whose toxicological exams are positive are handed DUID convictions without a trial. About a dozen states have per se marijuana laws. While this type of law is more cut-and-dried than an effect-based law, it is not without controversy when the drug in question is marijuana. This is because, for several reasons, there is a lack of consensus among forensic scientists about what level of THC concentration constitutes driving impairment.
The last type of driving under the influence of drugs law is a type of per se law, and it is called the zero tolerance per se law. Any amount of THC in your system under this law will constitute a DUID. This is the way some states are eliminating the limitations inherent in setting strict cut-off levels for drug metabolites or constituents. Zero tolerance per se laws are overly simplistic and not based on science, and about a dozen states have them.
Marijuana DUID laws, whether they are effect-based, per se, or zero tolerance per se, are controversial. And the order in which they are listed in the previous sentence reflects, from most to least difficult, the job the prosecutors have convicting people of violating them.
By Donna Westlund
Marijuana Policy Project