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Litigation Blog.
The seasoned lawyers and litigators at The Rubinstein Law Firm are here to share their insights with you.

Is there a legal THC limit for driving under the influence?

Ask just about anyone on the street and they could probably tell you the legal limit for blood alcohol content (BAC) for driving.

But with recreational marijuana expanding throughout the state, many people are wondering: do these same rules apply to driving while under the influence of drugs? And is there a THC legal limit of sorts, similar to the laws regarding alcohol?

Michigan’s current drugged driving laws

Even with the legalization of recreational marijuana, Michigan law makes it illegal to operate, navigate or be in control of a motor vehicle while “under the influence” of a Schedule 1 controlled substance – and yes, that includes cannabis.

If you’re pulled over on suspicion of drugged driving, you may wind up facing an operating while visibly impaired (OWVI), operating while intoxicated (OWI), or operating with any presence of a Schedule 1 drug or cocaine (OWPD) charge.

While the state also has a “zero tolerance” law, prohibiting someone from driving if they have any amount of a Scheduled 1 controlled substance in their system, recent court rulings have called the enforcement of this law into question.

Is there a legal THC limit?

Unlike with drunk driving and a motorist’s BAC, there is no specific test in Michigan that is used to determine a measurable legal limit for operating a motor vehicle with marijuana in your system. In fact, in 2019, Michigan’s Impaired Driving Safety Commission recommended against establishing one.

Why? Because there isn’t a “scientifically supported” level of THC in someone’s body that reliably indicates whether someone is impaired. Different individuals respond to THC in different ways, and if one person has built up a tolerance, a high level of THC might not mean they are legally impaired.

In addition, the way the body processes THC can make tests unreliable for judging impaired driving.

How do officers decide if someone is impaired?

Since no specific legal THC limit exists, it’s up to law enforcement officers and prosecutors to look at other evidence when determining whether to arrest or charge an individual. That might include:

  • The result of field sobriety tests, such as the one-leg stand
  • Observations of erratic driving, such as speeding or swerving
  • The smell of marijuana coming from a vehicle
  • The presence of drug paraphernalia

Of course, none of these things prove, with certainty, that someone was driving while impaired. There is a lot of room for authorities to try to interpret these small pieces of evidence as they see fit, rather than sticking strictly to the facts. Because of that, in these types of cases, it is vital to put up a strong defense as swiftly as possible.