Ketamine sits in an unusual place in American medicine. It is a dissociative anesthetic that has been used for decades in surgery and on battlefields, and it is now being prescribed, often through telehealth providers, as a treatment for depression, post-traumatic stress, and chronic pain. At the same time, ketamine remains a popular recreational substance and an analog of phencyclidine. I have begun seeing more Michigan motorists charged with operating while intoxicated based on the presence of ketamine in a blood sample. In my practice, these cases require very careful attention because the science, the statute, and the toxicology testing do not line up as neatly as a prosecutor often suggests.
I want to walk through how a Michigan ketamine OWI case actually works, where the prosecution's proofs commonly fall short, and why I am concerned that some defendants have pleaded guilty to charges that the prosecution might not have been able to prove had the case been fully litigated.
Why a Ketamine OWI Is Not a Standard "Drugged Driving" Case
Michigan's principal drugged driving statute, MCL 257.625, contains several distinct theories of liability. The OWI statute defines "operating while intoxicated" to include the situation in which "[t]he person is under the influence of alcoholic liquor, a controlled substance, or other intoxicating substance or a combination of alcoholic liquor, a controlled substance, or other intoxicating substance." MCL 257.625(1). A separate, lesser theory, operating while visibly impaired, applies when the operator's ability to drive is "visibly impaired" due to consumption of liquor, a controlled substance, or other intoxicating substance. MCL 257.625(3).
Michigan also has a "zero-tolerance" provision, MCL 257.625(8), which prohibits operating with any amount in the body of a controlled substance listed in schedule 1 under MCL 333.7212, or of a controlled substance described in MCL 333.7214(a)(iv). The Court of Appeals has explained that under MCL 257.625(1), an OWI prosecution requires proof of three elements: "(1) the defendant operated a motor vehicle (2) on a highway or other place open to the general public or generally accessible to motor vehicles (3) while under the influence of liquor or a controlled substance, or a combination of the two, or with [an unlawful bodily alcohol content]." People v Hyde, 285 Mich App 428, 447-448 (2009). The third element is disjunctive.
The schedule distinction matters a great deal in a ketamine case. Ketamine is classified as a Schedule III controlled substance with moderate to low potential for physical and psychological dependence. See Arango, et al., Increasing Prevalence of Ketamine in Drivers in New York City, 45 J Analytical Toxicology 799, 800 (2021). Schedule III is not Schedule 1. Schedule III is not the cocaine-related category in MCL 333.7214(a)(iv). For that reason, a ketamine prosecution cannot be charged under the zero-tolerance provision of MCL 257.625(8). The prosecutor must instead proceed under MCL 257.625(1) or MCL 257.625(3) and must prove actual influence or visible impairment.
This is a significant practical point. In People v Koon, 494 Mich 1 (2013), the Supreme Court explained that the Michigan Vehicle Code's "zero-tolerance provision, MCL 257.625(8), which is inconsistent with the [Michigan Medical Marihuana Act], does not apply to the medical use of marijuana." The Court also recognized that Michigan jurisprudence has carefully policed the line between "presence" and "under the influence." In People v Feezel, 486 Mich 184 (2010), the Court held that 11-carboxy-THC, a metabolite of marijuana, is not itself a schedule 1 controlled substance under MCL 333.7212. More recently, in People v Stock, 507 Mich 1008 (2021), the Supreme Court rejected the prosecution's effort to interpret "controlled substance" under MCL 257.625(8) to include "any metabolite of cocaine." These cases tell me, and should tell prosecutors, that the statutory categories must be applied with precision, not stretched to fit the chemistry of the moment.
What "Under the Influence" Actually Requires
Because a ketamine OWI ordinarily proceeds under MCL 257.625(1)(a) rather than the zero-tolerance provision, the prosecution must prove that the driver was "under the influence" of the drug. The governing language comes from People v Lambert, 395 Mich 296 (1975), in which the Supreme Court explained that operating under the influence is committed when a defendant drove with the "ability to drive [that] was substantially and materially affected by consumption of intoxicating liquor." As the Court of Appeals later summarized in Oxendine v Secretary of State, 237 Mich App 346, 353-354 (1999), "the threshold for [impaired driving] is much lower" than for the older OUIL offense, and an OWVI is committed when the defendant's "ability to drive was so weakened or reduced . . . that [the] defendant drove with less ability than would an ordinary, careful and prudent driver." That weakening "must be visible to an ordinary, observant person." Oxendine, 237 Mich App at 354 (quoting Lambert).
I explain this to clients carefully because non-lawyers often assume that a positive blood test for a drug is itself the offense. For a Schedule III substance like ketamine, the positive test is only one piece of the puzzle. The prosecution must still prove that the driver's ability to operate the vehicle was either substantially and materially affected (for OWI) or visibly impaired in a manner observable to others (for OWVI). The "evidentiary mandate compels a prosecutor to proffer evidence of a visual or observational nature, i.e., evidence describing or depicting actions, conduct, characteristics, or movements of the person during the pertinent time period, revealing an impaired ability relevant to operating a vehicle." Oxendine, 237 Mich App at 354 n 3 (paraphrasing). Without that observational proof, a ketamine case is much weaker than it may first appear.
The Michigan State Police Toxicology Unit and the Quantification Problem
When a Michigan officer obtains a blood draw, either with consent under MCL 257.625c or by warrant consistent with Missouri v McNeely, 569 US 141 (2013), and Birchfield v North Dakota, 579 US 438 (2016), the sample is sent to the Michigan State Police Toxicology Unit. For ketamine, the laboratory uses liquid chromatography-tandem mass spectrometry (LC/MS/MS) to identify the molecule. The MSP toxicology unit does not currently report a validated quantitative result for ketamine. The laboratory reports only that ketamine was detected. There is no number attached to the result that would allow a fact finder to assess how much ketamine was in the driver's blood.
This is a serious problem for the prosecution and an even more serious problem for an uninformed defendant. The peer-reviewed literature makes clear that the relationship between ketamine and impairment is dose-dependent and concentration-dependent. In a controlled simulator study, Hayley and colleagues observed that whole blood ketamine concentrations rose from a mean of 0.34 mg/L following a low-range analgesic dose to a peak of 0.82 mg/L following the highest infusion step, and that there was only a "weak positive linear association" between whole blood ketamine concentrations and standard deviation of lateral position, with an R² of 0.11. Hayley, et al., The acute and residual effects of escalating, analgesic-range doses of ketamine on driving performance: A simulator study (2018). In a Hong Kong field-impairment study, the authors found that when salivary ketamine concentrations exceeded 300 ng/mL, the field impairment test detected impairment in roughly nine out of ten subjects, while at lower concentrations, only about half were identified as impaired. Cheng, et al., Roadside detection of impairment under the influence of ketamine, 170 Forensic Sci Int'l 51 (2007). The same study reported that chronic ketamine users with measurable ketamine in the body still passed the test, consistent with tolerance.
What this scientific literature tells me, and what I explain to clients, is that the presence of ketamine in blood does not automatically translate into impaired driving. Concentration matters. Time of dosing matters. Tolerance matters. Co-administered drugs matter. When the laboratory reports only that ketamine is present, without a quantitative result, the fact finder is left to assume the worst. A jury hears the word "ketamine," and the substance does the work that scientific evidence ought to do.
Relevance, Unfair Prejudice, and the Bowden Problem
When I evaluate a ketamine case, the evidentiary rules in MRE 401, MRE 402, and MRE 403 are central. Evidence is relevant if it "has any tendency to make a fact more or less probable than it would be without the evidence" and if "the fact is of consequence in determining the action." MRE 401. Even relevant evidence may be excluded under MRE 403 "if its probative value is substantially outweighed by a danger of one or more of the following: unfair prejudice, confusing the issues, misleading the jury, undue delay, wasting time, or needlessly presenting cumulative evidence." Michigan courts recognize that "[u]nfair prejudice exists when there is a tendency that evidence with little probative value will be given too much weight by the jury." People v McGhee, 268 Mich App 600 (2005). The probative value of a non-quantified ketamine result is significantly lower than the probative value of a quantitative blood-drug result, while the prejudicial impact of the word "ketamine" on a jury is not in serious dispute. In my view, that imbalance deserves a serious MRE 403 challenge in the right case.
Expert testimony presents another set of issues. MRE 702 codifies the gatekeeping function adopted from Daubert v Merrell Dow Pharmaceuticals, Inc, 509 US 579 (1993), and recognized in Michigan in Gilbert v DaimlerChrysler Corp, 470 Mich 749 (2004). The trial court's role under MRE 702 "imposes a fundamental duty to ensure that the proffered expert testimony is both relevant and reliable." People v Muniz, 343 Mich App 437 (2022). In the drug recognition context, the Court of Appeals in People v Bowden, 334 Mich App 171 (2022), held that the prosecution failed to show that the drug recognition expert protocol had been validated as a reliable method for demonstrating a person's level of impairment due to marijuana, or the degree to which a driver's abilities could be diminished by any given level of marijuana. The same critique applies with at least equal force to ketamine, which the DRE program treats within the dissociative anesthetic category along with PCP. A DRE may be able to describe observations, but the leap from observation to a reliable opinion about ketamine-induced driving impairment is one the proponent must justify under MRE 702 and Daubert.
Investigative Stages and the Fourth Amendment
Every ketamine case begins with an investigative encounter, and the stages of that encounter must be analyzed separately. The traffic stop itself is a seizure that requires reasonable suspicion. The expansion of the stop into a drug investigation must be supported by additional, articulable observations. An arrest requires probable cause. A search of the blood is itself a Fourth Amendment event. People v Perlos, 436 Mich 305, 313 (1990) ("[A] blood test conducted under the direction of police falls within the ambit of the Fourth Amendment."). Although Michigan's implied consent statute, MCL 257.625c, applies once a qualifying arrest is made, the United States Supreme Court has held that a warrant is generally required for a blood draw absent valid consent or exigent circumstances. Missouri v McNeely, 569 US 141 (2013); Birchfield v North Dakota, 579 US 438 (2016). I do not blur these categories when I review a file. Each stage gets its own analysis.
What Facts Typically Matter in Litigation
When I assess a Michigan ketamine OWI charge, I look at what the officer actually observed before the stop, what the officer said the driver did during the encounter, how field sobriety tests were administered, whether a drug recognition evaluation was performed, what the DRE concluded and how the conclusion was documented, the lawfulness of the blood draw, the chain of custody, the laboratory's qualitative report, the validation and scope of the LC/MS/MS method, and whether there are any quantitative observations at all. I also consider whether the driver has a legitimate prescription, what the dose and route of administration were, when the last administration occurred, and whether other substances were present. Polypharmacy is common in the ketamine literature; the Arango study reported that the most common drug classes detected with ketamine in DUID cases were cannabinoids, ethanol, benzodiazepines, cocaine, and amphetamines.
NOTE: A valid ketamine prescription is not dispositive. You are not required to prove that you had a prescription or that you legally ingested ketamine as a defense to a Michigan OWI charge.
None of these inquiries guarantees a particular outcome. A motion to suppress or to exclude the blood result, a Daubert challenge under MRE 702, an MRE 403 motion, or a thorough cross-examination of an MSP analyst may preserve issues, frame legal disputes, narrow the evidence the jury will hear, or position the case for a favorable resolution. Motion practice does not promise a result. It does, however, ensure that the prosecution is required to prove what the statute requires.
Conclusion
Ketamine cases in Michigan deserve more careful handling than they often receive. Because ketamine is a Schedule III controlled substance, the zero-tolerance provision of MCL 257.625(8) does not apply. The prosecution must therefore prove actual influence or visible impairment under MCL 257.625(1) or MCL 257.625(3). When the Michigan State Police Toxicology Unit reports only the presence of ketamine without a validated quantitative measurement, the gap between "detected" and "impaired" becomes very large, and the scientific literature shows that the gap is real. I have seen people accept pleas to ketamine OWI charges without understanding that the laboratory could not say how much ketamine was in their body, and without their counsel raising the evidentiary, scientific, and constitutional issues that the case presents. Every Michigan OWI charge involving ketamine should be evaluated on its own facts, with attention to the statutory framework, the toxicology, and the rules of evidence. That kind of case-by-case review is what these prosecutions require.
