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With recreational and medical marijuana legal, many people think the laws around driving under the influence of cannabis have changed. This is a common and dangerous misunderstanding. Michigan law
is clear: operating a vehicle while under the influence of marijuana remains illegal.
The legal issue is that the drug must impair driving ability. Unlike alcohol, where a specific Blood Alcohol Content (BAC) percentage is all the prosecution needs, marijuana cases involve different standards.
Michigan’s Operating While Intoxicated (OWI) Standard
In Michigan, an impaired driving charge is called Operating While Intoxicated (OWI), although people still use terms like DUI (Driving Under the Influence) or DWI (Driving While Intoxicated). Michigan Compiled Law establishes that a person shall not operate a vehicle while under the influence of a controlled substance, including marijuana.
The critical difference from alcohol cases is that Michigan does not have a set legal limit for the amount of THC (tetrahydrocannabinol, the primary intoxicating compound in cannabis) that proves you are too impaired to drive. The focus is on your actual ability to operate the vehicle.
The “Substantially Lessened” Test
To secure a conviction for an OWI involving marijuana, the prosecutor must prove that the consumption of the controlled substance substantially lessened the defendant’s ability to drive.
The police and prosecutor rely heavily on observational evidence, such as:
- The driver’s manner of operating the vehicle (e.g., swerving, running a light).
- The driver’s performance on Field Sobriety Tests (FSTs).
- The officer’s observations of the driver’s appearance (e.g., bloodshot eyes, slurred speech).
This shift from a BAC number to an officer’s subjective observation and forensic evidence is what makes these cases uniquely challenging to both prosecute and defend.
How Marijuana Legalization Impacts OWI
The legalization of recreational and medical marijuana under the Michigan Regulation and Taxation of Marihuana Act (MRTMA) did not change the OWI law. The law explicitly states that it does not authorize a person to operate a vehicle while under the influence of marijuana.
Protections for Medical Marijuana Patients
If you are a registered qualifying patient under the Michigan Medical Marihuana Act (MMMA), you have a limited defense against the OWPD “presence of THC” charge.
The prosecutor must prove that the marijuana in the patient’s system substantially lessened their ability to operate the vehicle. Simply having THC in your blood is not enough for a conviction. The officer’s field observations and the amount of THC found in your blood will be crucial evidence.
Challenges in Marijuana Impairment Testing
One of the biggest battlegrounds in a Michigan OWI marijuana case is the chemical test. Unlike alcohol, where breathalyzers are reliable for BAC, testing for marijuana impairment presents several forensic and legal hurdles.
The Problem with THC Metabolites
THC is fat-soluble, which means it can remain detectable in a person’s system, particularly in blood and urine, for days or even weeks after the intoxicating effects have worn off.
A positive blood test for inactive THC metabolites does not definitively prove impairment at the time of the stop. It only proves that the person consumed cannabis sometime in the past. This ambiguity is why Michigan courts rely heavily on the officer’s observations of driving behavior and FSTs.
Roadside Oral Fluid Testing
Law enforcement in Michigan sometimes uses preliminary oral fluid tests at the roadside to detect the recent presence of controlled substances, including THC.
While these tests are quick and non-invasive, they only screen for the presence of the drug, and they do not establish a legal level of impairment. A positive preliminary result merely provides the officer with additional information to support the request for a more definitive chemical test.
The Implied Consent Law and Blood Draws
In Michigan, if you are arrested for an OWI, the Implied Consent Law applies. By operating a motor vehicle in the state, you are considered to have given consent to a chemical test (blood, breath, or urine) if you are arrested for OWI or a related charge.
- Refusing the Test: If you refuse to take a chemical test after being arrested, you face an automatic one-year suspension of your driver’s license, even if you are later found not guilty of the criminal charge.
- Warrantless Blood Draws: While a police officer must generally obtain a warrant to compel a blood draw, courts sometimes allow exceptions based on the exigent circumstances of THC rapidly dissipating from the bloodstream. This is a complex area of Fourth Amendment law that often forms the basis for legal challenges in OWI cases.
Manley & Manley Attorneys Deliver Superior Results
In a recent Livingston County case, Manley & Manley defended against charges of Operating While Under the Influence of Marijuana Causing Death, a felony punishable by up to 15 years in prison. Blood results from the driver showed the presence of marijuana following a traffic accident that left four people dead. Through skilled cross-examination of witnesses at a Preliminary Examination hearing, Manley & Manley attorneys established that, although the Defendant’s blood results provided evidence of marijuana use, the Defendant exhibited no signs of impairment following the accident.
Our attorneys presented extensive research and precedential rulings and the Court. The cases presented to the court showed that in cases with an even higher level of marijuana in the blood than the Defendant’s the Court’s have held that without objective evidence of impairment, the blood results are not enough. The Livingston County Judge agreed that there was a lack of evidence to send our client’s case to trial. After applying those rulings to the Defendant’s case, all charges were dismissed.
Securing Your Right to Defend Your Future
The stakes in a marijuana OWI case are incredibly high, carrying penalties that can include jail time, steep fines, license suspension, and required community service. Given the confusing legal standards around THC and the unreliability of field testing, you cannot afford to face these charges alone.
The team at Manley & Manley understands local court procedures and how to effectively challenge every piece of evidence the prosecution presents. We work to build a defense that protects your license, your record, and your future.
If you are facing a marijuana OWI charge in or around Flint, call us now for a confidential discussion about your case at 810-374-0240. We are here to fight for you.
