How Sober Cannabis Users are Wrongfully Convicted of Intoxicated Driving

Police in Michigan continue to use unreliable chemical and field sobriety tests when investigating drivers suspected of using cannabis. This can lead to sober cannabis users being wrongfully convicted of intoxicated driving. This is because the tools used for decades to investigate drunk driving cases simply do not translate well to the investigation of drivers believed to be under the influence of marijuana.

These conclusions are drawn from a 2020 research study conducted by the National Institute of Justice. This federally funded research study resulted in the production of a final written overview which was subsequently submitted to the U.S. Department of Justice. The title of the overview is Differences in Cannabis Impairment and its Measurement Due to Route of Administration. (Hereafter “NIJ Study”).

What did the NIJ Study Conclude?

According to the NIJ Study, THC levels measured in biofluids such blood, urine and salvia were not reliable indicators of marijuana intoxication. Furthermore, the field sobriety tests used in drunk driving investigations were also not reliable or effective in detecting marijuana intoxication.

Prior to the legalization of marijuana in 2008 it was unlawful in Michigan to have any amount of THC in your blood stream while operating a motor vehicle.  Now that we have legalized both recreational and medical marijuana prosecutors must prove that the THC found in your blood or urine actually caused impairment. This NIJ Study demonstrates that the tools and evidence used in drunk driving prosecutions do not translate well into the prosecution of driving under the influence of marijuana cases.

How do Police Investigate Drivers Suspected of Being Under the Influence of Marijuana?

Just as with drunk driving investigations, no absolute standards exist for the investigation of drivers believed to be under the influence of marijuana. However, most of Michigan’s police officers, prosecutors and judges approach the investigation and prosecution of cannabis impaired drivers the same way they approach drunk drivers.

Consequently, the investigation and prosecution of both kinds of cases involve a combination of field sobriety tasks and chemical tests. For the most part, the field sobriety tasks utilized in marijuana intoxicated driving cases are the same as those utilized for drunk driving cases. These include the walk and turn, one leg stand, horizontal gaze nystagmus, and the modified Romberg test. While questions remain as to whether these tests are even reliable indicators of alcohol intoxication, there is little doubt surrounding the premise that these tests do not reliably predict, let alone demonstrate, cannabis intoxication.

As it relates to chemical tests, the essential problem is that given THC levels are poor indicators that a person is in fact under the influence of the drug. While predictions can be drawn regarding how .08 bodily alcohol level will impact things such as one’s ability to divide attention or perform relevant psycho-motor tasks, the same cannot be said of a given THC level. This is the reason some states, including Michigan, have decided not to create a THC legal limit.

What is Different about Marijuana and THC?

The simple answer is almost everything. Stated a little more scientifically, one of the many problems with using the tools of a drunk driving case to investigate a driving under the influence of marijuana case is that the pharmacokinetics (what the body does to the drug) and the pharmacodynamics (what the drug does to the body/brain) of marijuana and alcohol are almost completely different.

Alcohol is almost universally consumed orally, whereas marijuana can be smoked, consumed orally, including sublingually, transdermally, or vaped. These various methods of administering THC and delivering it to the brain through the blood all lead to different times of onset, different time periods for both onset of effect and duration, and differences in intensity, type and length of effect.

Additionally, the human brain responds in a mostly universal way to a given dose of alcohol.  This is partly way charts have been developed for the kinds of symptoms one would expect between given BAC ranges. For example, according to Kurt Dubowski, at .03-.12 one might expect mild euphoria, sociability, talkativeness, some sensory-motor impairment, etc.  See, Garriott’s Medical Legal Aspects of Alcohol, pg. 28. (2008).

Scientists have yet to produce a chart like this for given ranges of THC blood levels. One reason for this is that, unlike the zero order kinetics applicable to alcohol, the phamacokinetics of THC involve first order kinetics.  Simplified this means that, unlike alcohol, people become metabolically and behaviorally tolerant to THC.  This fact might help to explain why at least one study found that marijuana alone did not impair driving. Id at pg 38, citing a 1983 study by Sutton (entitled The effects of alcohol, marijuana and their combination on driving ability).

How Your Lawyer Can Use This Information in the Defense of Your Case

Effectively using this information will require a sophisticated understanding of the underlying scientific principles specific to marijuana, combined with an innovative and creative application of this knowledge to the facts and circumstances of your case. The Michigan cannabis lawyers at the Barone Defense Firm possess this expertise and combine it with these attributes.

If you have been charged with driving under the influence of marijuana, contact one of the Michigan DUI lawyers at the Barone Defense Firm for your free case analysis.

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