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Will Michigan Create a Legal Limit for Marijuana and Driving?

June 16, 2019 DUI/OWI/DWI

Everyone knows the legal limit for drinking and driving is .08. Could a limit be established for marijuana and driving? With marijuana’s newfound legal status, there is a lot of attention on enforcement of drugged driving cases.

Proposed Law

A new proposed law would create a legal limit for marijuana at 5 nanograms. This means a person would be legally intoxicated by marijuana if there were 5 nanograms of THC in their blood while driving.

The law would also include THC metabolite in the amount of 5 nanograms. Currently, THC metabolites are not used against a person at trial. This is because a metabolite is not active in the bloodstream. A metabolite means the person had used the substance in the past, but the substance is not actively making the person high. This would create an easier avenue for prosecutors to convict drivers of operating while intoxicated by marijuana. Read the amendments to the OWI law here.

What this means is anyone who has smoked marijuana anytime in the recent past, even while not high, could be found guilty of operating while intoxicated. This proposed law is dangerous, because it could lead to a guilty verdict even where a person was not impaired by marijuana or maybe had not even smoked in the very recent past.

This proposed law misunderstands the science of marijuana.

Is This Legal Limit Backed by Science?

The Michigan Impaired Driving Safety Commission recently examined this issue and reported to Michigan lawmakers. The Commission’s job was to investigate whether Michigan should establish a legal limit for marijuana and driving and what that limit should be. The Commission declined to recommend a legal limit.

There were two reasons for this recommendation. First, the Commission did not believe there was a direct link between impairment and the amount of THC in a person’s system. This is because a person’s tolerance to marijuana varies based on use. 5 nanograms to one person is not the same for another person. There is no easy formula to predict impairment based on amount. And second, the Commission found difficulties in measuring blood THC because THC dissipates from the blood quickly. A blood test two hours after a person was driving may not accurately tell us what was in their blood two hours ago.

This proposed law obviously disregards the Commission recommendation.

Legally Speaking

Essentially right now, for a person to be in trouble for operating while intoxicated by marijuana, the driver must be “under the influence” of marijuana. This means the person must be actually impaired by marijuana. Under a system with a legal limit, a person could be guilty of operating while intoxicated if they have over 5 nanograms, even if the person is not impaired by marijuana.

Where a person has over 5 nanograms of metabolite in their system, the person may not even have smoked marijuana during the day before their arrest. A metabolite shows that a person smoked marijuana in the past, but the metabolite without active THC means the person does not have active THC in their system. A person cannot be high on metabolites alone.

A legal limit for marijuana would bring marijuana-driving law in line with how the law treats alcohol and driving. A person can be per se legally intoxicated by alcohol if they have a blood alcohol content of over .08. In addition, a person could be guilty of operating while intoxicated by alcohol if they are over .08 even if they don’t show signs of impairment.

What Do Other States Do?

A number of other states have legalized recreational or medical marijuana. Here are some other states and what their legal limits look like:

  • Colorado – 5ng
  • Montana – 5ng
  • Nevada – 2ng
  • Ohio – 2ng
  • Pennsylvania – 1ng
  • Washington – 5ng

ArborYpsi Law will continue to follow all developments and will keep you posted.

Call us

Call Sam Bernstein at 734-883-9584 or e-mail at

Sam Bernstein is a Criminal Defense Attorney in Washtenaw County.

ArborYpsi Law is located at 4158 Washtenaw Ave., Ann Arbor, MI 48108.

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