Evidence in Michigan drugged-driving cases

In a Michigan drugged-driving case, what the prosecution must prove depends on which part of the OWI statute is charged: under MCL 257.625(1) it must prove the driver was "under the influence" of a controlled or other intoxicating substance, while under 625(8) it must prove the driver had "any amount" of a schedule 1 drug or cocaine in the body, without proof of impairment.^[1][3] Because the Vehicle Code sets no numeric THC limit, the evidence offered in these cases can include blood toxicology, observations and expert testimony, each subject to its own legal rules.^[4][8]

This page covers how that evidence is treated. The offenses themselves are explained in driving under the influence of drugs.

Three ways a drug case can be charged

Charge	What must be proved about the drug
OWI, under the influence (625(1)(a))	The person was under the influence of alcohol, a controlled substance, another intoxicating substance, or a combination.[1] Jurors are told this means the ability to drive normally was substantially lessened.[10]
Visibly impaired, OWVI (625(3))	Because of a substance, the ability to operate was visibly impaired; jurors are told the ability to drive must have been lessened to the point another person would notice.[2][11]
Any amount (625(8), "OWACS")	The person had in the body any amount of a schedule 1 controlled substance or cocaine; jurors must find the specific substance the prosecutor alleged.[3][12]

"Intoxicating substance" covers substances other than alcohol or controlled substances that are recognized drugs in the official pharmacopoeias, or non-food substances, including vapors or fumes, used in an unintended way that may cause intoxication.^[13] "Controlled substance" takes its meaning from the Public Health Code.^[14]

When an OWI or OWVI charge rests on a drug, the jury (or the judge on a plea or bench trial) must make a specific finding whether drugs were involved, and a drug finding is reported to the Secretary of State.^[15]

Proving "any amount": schedule 1 drugs, metabolites and toxicology

Section 625(8) turns on what the lab found in the body. Several Michigan Supreme Court decisions limit what counts:

• THC metabolite. In People v Feezel (2010), the Court held that 11-carboxy-THC, "a byproduct of metabolism created when the body breaks down the psychoactive ingredient of marijuana," is not a schedule 1 controlled substance.^[5] Its presence alone therefore does not prove the any-amount offense.^[16]
• Cocaine metabolite. In People v Stock (2021), the Court reversed OWI-causing-death and serious-injury convictions where the prosecution showed only an unidentified cocaine metabolite in urine, without evidence supporting an inference that cocaine itself was in the body.^[6]
• Marijuana's schedule. The Public Health Code still lists marihuana in schedule 1, except marihuana handled in compliance with the act and as authorized by federal authority, which is schedule 2.^[17]

The State Police rules for blood and urine testing list accepted lab methods, including gas chromatography for ethanol and LC/MS, GC/MS and immunoassays for drugs, and require daily control samples, with control results kept at least 1 year.^[18] Blood alcohol results are expressed per 100 milliliters, and serum or plasma results must be converted to whole-blood equivalents.^[19] Collection must be witnessed, labeled and sealed, with a sodium fluoride preservative tube and no alcohol skin swab.^[20] Only a licensed physician, or a qualified person acting under a physician's delegation in a medical environment, may draw blood at an officer's request.^[21] For blood procedures, see blood tests in OWI cases; for THC specifically, THC blood tests and impairment.

Marijuana: medical patients, recreational users and drivers under 21

The rules for marijuana differ by who the driver is:

• Registered medical patients. Under People v Koon (2013), the Medical Marihuana Act supersedes 625(8) for a registered patient acting within the Act, allowing the patient to drive with marijuana in his or her system so long as the patient is not otherwise under the influence.^[22] The Act does not authorize driving under the influence.^[23] Patients may be prosecuted for OWVI (Dupre, 2020).^[24]
• Adult recreational users. The 2018 recreational law (effective December 6, 2018) does not authorize driving under the influence or consuming marijuana while driving.^[25] Whether Koon's holding extends to recreational users is described by the Traffic Benchbook as unclear.^[26]
• Drivers under 21. The Court of Appeals held in People v Perry (Docket No. 355330, August 12, 2021) that the recreational law did not remove criminal penalties for drivers under 21 with marijuana in their system; the 18-year-old driver in that case had 4 nanograms of THC per milliliter of blood.^[27]

More detail is on marijuana and driving.

Proving impairment without a number

For under-the-influence and visibly-impaired charges, the prosecution relies on evidence of how the driver's abilities were affected. The jury instruction tells jurors to consider the defendant's mental and physical condition when driving, including reflexes, vision, walking, talking, manner of driving and judgment, and whether any abnormality was caused by alcohol or drugs.^[28] In an alcohol case, the Court of Appeals held OWVI does not require proof of erratic driving; signs observed at the stop and on video were enough to go to a jury.^[29] The chemical-test rules do not limit other admissible evidence of impairment.^[30]

Roadside tools have limits. Standardized field sobriety tests count as "standardized" only if given in substantial compliance with federal standards.^[31] The statute authorizes the roadside oral-fluid test only for officers certified as drug recognition experts in counties participating in a pilot program, and its results have limited trial uses like the PBT.^[32][33] The State Police's own pilot report said a roadside oral-fluid result, positive or negative, "does not determine if a driver is impaired or not impaired."^[34] See roadside oral-fluid drug tests.

Drug recognition experts and expert testimony

The statute defines a certified drug recognition expert (DRE) as a law enforcement officer trained to recognize impairment from a controlled substance rather than, or in addition to, alcohol.^[35] In People v Bowden (2022), a DRE described a 12-step protocol and 7 drug categories in testimony; that description is the witness's account, not a holding of the court.^[36]

The holding in Bowden concerned admissibility. The Court of Appeals reversed an order letting the DRE testify that the driver was impaired by marijuana to a degree that made her unsafe to drive, because "the prosecution failed to establish any valid connection between the use of the DRE protocol and a conclusion regarding the degree to which a person's driving ability was diminished by the use of marijuana."^[7] The court also said the "expert" label in DRE certification does not decide admissibility under MRE 702.^[7]

MRE 702 applies to every expert in a drug case, including toxicologists for either side. The party offering the expert must show the court it is more likely than not that the testimony will help the jury, rests on sufficient facts or data, is the product of reliable principles and methods, and reliably applies them to the case.^[8] If an expert does testify, jurors are told they "do not have to believe an expert's opinion" and should weigh the reasons, facts and qualifications behind it.^[9] See drug recognition experts.

Getting the lab results

On a written request filed with the court, the prosecution must furnish chemical-test results at least 2 days before trial, and failure to fully comply bars the prosecution from using them.^[37] When a blood result is pending at arrest and later shows no unlawful alcohol or drug, the officer must notify the person and mail the license back.^[38] Practical step: keep every notice you receive about a pending blood result, since it shows when the sample was taken and by whom.

Common misunderstandings

• "Legal marijuana means driving with THC is legal." Marijuana is still schedule 1 for 625(8), and the recreational law does not authorize impaired driving.^[17][25]
• "Any positive drug test proves the case." An inactive THC metabolite is not schedule 1, and an unidentified cocaine metabolite was not enough in Stock.^[5][6]
• "A DRE's opinion is always admissible." Bowden excluded a DRE opinion on the degree of marijuana impairment.^[7]
• "No number means no case." Under-the-influence and OWVI charges can be proved by observations and other evidence.^[30][29]

For prescription medications, see prescription and over-the-counter drugs.