Determining how much hash makes you totally smashed


Marie E. Matyjaszek

Everyone knows the basic concept of whether or not a person is illegally drinking and driving – he or she is over the “limit.” Their bodily alcohol content, or BAC, is higher than what is legally allowed, and consequently, their driving is considered to be a danger to others based on their impaired state. In Michigan, when a person’s BAC is 0.08 or higher, it is illegal to drive.

State Representative Pamela Hornberger wants to create a similar law for marijuana – essentially, setting a level for how much is too much weed to get behind the wheel. While it is illegal to drive while intoxicated with drugs or alcohol, there is no clear definition of the limit of marijuana one can have in his system. And let’s not forget you can drive like a looney toon but be completely sober and still face legal consequences (you don’t need to be intoxicated to be a lousy driver).

Fueled by the 2020 death of a girl who was hit and killed by an individual who was driving with THC in her system, Hornberger is sponsoring HB 4727 in an effort to prevent more senseless deaths. Michigan’s self-proclaimed “nerd” governor Rick Snyder formed the Impaired Driving Safety Commission to study the possibility of determining levels of intoxication as it related to THC. In 2019, the Commission issued its report, which determined that “there is no scientifically supported threshold of…THC bodily content that would be indicative of impaired driving.”

The report referenced the difficulty in accurately determining impairment based on an individual’s blood concentrations of THC. To just pick a number would ignore the impact of frequent users who have to ingest more marijuana to achieve the same effect as a person who just started using. THC levels can vary significantly from the time of blood collection versus the levels when the individual was actually driving. It concluded that a roadside sobriety test was the best way to determined impairment.

The bill would create a limit of 5 nanograms per milliliter of blood when determining if an individual is intoxicated from the use of marijuana. The 2019 report noted that Colorado, Montana, Nevada, Ohio, Pennsylvania and Washington all had impaired driving levels for THC. Colorado, Montana and Washington share what HB 4727 proposes at 5 nanograms per milliliter. Nevada and Ohio have a 2-nanogram per milliliter limit, and Pennsylvania is the lowest at 1 nanogram per milliliter. Colorado adds a twist in that its limit is “a reasonable inference. ...[which] allows a jury to infer that a driver was impaired if his or her blood test result is 5 more ng/ml…but that inference can be rebutted by the defendant in legal proceedings with evidence to the contrary.”

As a definite number was not recommended in 2019, it will be interesting to see if the bill has any success given that it has only been two years since the commission’s report. While driving under the influence of any drug or alcohol can be illegal, it has to be accurately quantified before the law should interfere.


Marie E. Matyjaszek is an attorney referee at the Washtenaw County Friend of the Court; however, the views expressed in this column are her own. She can be reached by e-mailing her at

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