OWI Blood Test Cases
In Michigan OWI cases, blood testing is often treated as the strongest form of chemical evidence. Prosecutors like blood because it appears direct, scientific, and difficult to dispute. A breath test estimates blood alcohol through a biological conversion from breath alcohol to blood alcohol. A blood test, by contrast, measures alcohol or drugs in a sample of the person’s actual blood. That is why blood testing is often described as the “gold standard” in forensic alcohol testing.
But “gold standard” does not mean immune from challenge. In my practice, I look at blood test cases from two separate directions. The first is constitutional and statutory: was the blood lawfully obtained? The second is forensic: was the blood properly collected, preserved, transported, tested, and interpreted? A blood test may be powerful evidence, but it is still evidence. It must be obtained lawfully, handled properly, and explained accurately.
Blood Testing Is Direct, But It Is Also Intrusive
The principal advantage of blood testing is that it directly measures the contents of a blood sample. That makes it different from breath testing, which depends on assumptions about the relationship between alcohol in deep lung breath and alcohol in circulating blood. Blood testing avoids the breath-to-blood conversion problem. When the sample is collected, preserved, and tested properly, it can provide significant evidence of bodily alcohol content or the presence of drugs.
That advantage comes with a serious legal cost. A blood draw is a physical intrusion into the body. It requires a needle, trained medical personnel, and the removal of biological material for use in a criminal prosecution. For that reason, I do not treat a blood draw as a routine administrative step. It is a search. When the government obtains blood for an OWI prosecution, the question is not merely whether the blood result is high or low. The first question is whether the government had lawful authority to obtain the sample in the first place.
In most OWI investigations, blood is obtained in one of three ways. The officer may obtain a search warrant. The officer may claim that the driver voluntarily consented. Or the officer may invoke Michigan’s implied-consent law. Each route creates different issues. A warrant requires probable cause and judicial authorization. Consent requires proof that the consent was voluntary and not mere submission to police authority. Implied consent requires compliance with the statute that creates and limits that consent.
Michigan’s Implied-Consent Law Has Limits
Michigan’s implied-consent law appears in MCL 257.625c. In general terms, a person who operates a vehicle on a public highway or other place open to the general public or generally accessible to motor vehicles is considered to have consented to chemical testing under specified circumstances. Those tests may include blood, breath, or urine, depending on the situation. But the statute does not give police unlimited authority to demand blood from every arrested driver.
One limitation is particularly important in blood-draw cases. MCL 257.625c(2) provides: “A person who is afflicted with hemophilia, diabetes, or a condition requiring the use of an anticoagulant under the direction of a physician is not considered to have given consent to the withdrawal of blood.” That language matters. A person who falls within that subsection has not given implied consent to a blood withdrawal. The officer may still seek a warrant if probable cause exists, but the officer cannot simply rely on implied consent to obtain blood from a person the statute excludes.
This issue was addressed directly in People v Hyde, 285 Mich App 428 (2009). In Hyde, the officer knew that the defendant was diabetic, but the officer did not understand the statutory exception. The officer gave implied-consent warnings and told the defendant that refusal would carry the civil consequences associated with Michigan’s implied-consent law. The Court of Appeals held that the resulting blood evidence had to be suppressed. The Court explained that the officer was unaware of the diabetes exception, erroneously instructed the defendant that refusal consequences would apply, obtained consent on the basis of that incorrect information, and did not obtain a search warrant or take steps to do so. Hyde, 285 Mich App at 441.
Hyde is important because it did not turn on whether the police had a weak case. The Court recognized that there was substantial probable cause and that the same blood evidence might have been obtained by warrant. The problem was that the police were not pursuing a warrant when they obtained invalid consent. The Court refused to use inevitable discovery to excuse the officer’s statutory and constitutional mistake. Hyde, 285 Mich App at 444-445.
That principle has direct consequences for OWI blood cases involving diabetes, hemophilia, or prescribed anticoagulants. If the officer invokes implied consent, fails to provide accurate chemical-test rights, and demands blood from a person who is not considered to have impliedly consented to blood withdrawal, the prosecution should not be permitted to treat the blood draw as voluntary consent. The issue is not whether the person eventually extended an arm. The issue is whether the person made a free and voluntary choice, or merely submitted to an asserted claim of legal authority.
Consent Is Not the Same as Acquiescence
Consent is one of the most frequently litigated issues in blood-test cases. When the prosecution relies on consent to justify a warrantless search, it bears the burden of proving valid consent. The consent must be unequivocal, specific, free of coercion and duress, and intelligently given. People v Farrow, 461 Mich 202 (1999); People v Bolduc, 263 Mich App 430 (2004); People v Dagwan, 269 Mich App 338 (2005). The government cannot satisfy that burden merely by showing that a person submitted after being told that the law required compliance. Bumper v North Carolina, 391 US 543, 548 (1968).
That distinction is essential in OWI cases because implied-consent warnings carry significant consequences. A driver who refuses a chemical test may face driver’s license sanctions and other administrative consequences. Michigan courts have recognized the coercive character of that choice. People v Wurm, 158 Mich App 265, 271 (1987), described the decision as a “Hobson’s choice,” and People v Weaver, 74 Mich App 53, 62 (1977), recognized the coercive effect of implied-consent penalties.
That does not mean every implied-consent blood draw is unlawful. It means the statutory framework must be followed. If the officer has probable cause and obtains a valid search warrant, the case presents one set of issues. If the officer properly invokes implied consent in a case where the statute applies, the case presents another. But if the officer uses implied-consent warnings to obtain blood from a person the statute expressly excludes, the defense should examine whether the blood evidence is the product of an unlawful warrantless search.
Timing and Relevance of the Blood Draw
Blood testing also raises timing issues. The longer the delay between driving and the blood draw, the more complicated the interpretation becomes. A blood alcohol result measures the alcohol concentration at the time the blood was drawn, not necessarily at the time of driving. Depending on absorption, distribution, and elimination, the person’s alcohol level at the time of driving may have been higher, lower, or approximately the same as the later test result.
This does not mean Michigan courts automatically exclude delayed blood tests. They generally do not. But delay affects weight, interpretation, and expert analysis. In some cases, the prosecution may attempt retrograde extrapolation, working backward from the test result to estimate the person’s blood alcohol level at the time of driving. That kind of opinion depends on assumptions about drinking pattern, time of last drink, food consumption, absorption status, elimination rate, body weight, and other individual factors. If those assumptions are missing or unreliable, the extrapolation may be weaker than it first appears.
Delay also matters because blood is biological evidence. Blood samples must be collected in appropriate tubes, mixed with preservative and anticoagulant when required, sealed, labeled, stored, transported, and tested under laboratory conditions that minimize degradation or contamination. If glucose is present and preservation is inadequate, fermentation can become an issue. Fermentation can produce alcohol after the blood is drawn. That alcohol may be chemically indistinguishable from alcohol consumed before driving unless the laboratory method and surrounding facts allow a meaningful interpretation.
Hospital Blood Is Different From Forensic Blood
Some OWI cases involve hospital blood rather than blood drawn primarily for law enforcement purposes. This usually occurs after a crash, when medical personnel draw blood for diagnosis or treatment. Hospital blood can be important evidence, but it creates its own problems.
Hospitals draw blood to treat patients, not to build criminal cases. The testing method may be different from the method used by a forensic laboratory. Speed may matter more than forensic precision because doctors need information quickly. Hospital records may contain warnings or disclaimers indicating that the results are not intended for legal purposes. Those disclaimers do not automatically make the evidence inadmissible, but they are important in evaluating reliability, foundation, and weight.
Hospital blood also raises interpretation issues in trauma cases. Medical treatment, injury, shock, medications, and fluids may complicate the meaning of a hospital alcohol result. The defense must examine what was drawn, who drew it, what test was performed, what instrument was used, whether the result reflects serum or whole blood, whether any conversion was applied, and whether the medical record supports the conclusion the prosecutor wants the jury to draw.
Laboratory Blood Testing Requires Witnesses and Documentation
Forensic blood testing is document-heavy. A proper review requires more than the final laboratory report. I want to see the blood draw kit documentation, the officer’s request, the hospital or phlebotomy records, the chain of custody, the laboratory submission form, storage records, instrument data, calibration materials, quality-control records, chromatograms, batch data, analyst notes, and the laboratory’s relevant procedures.
The need for documentation is not a technicality. Blood testing depends on process. The final number is the product of collection, storage, transport, preparation, instrumentation, analysis, review, and reporting. If the prosecution wants the jury to rely on the number, the defense is entitled to examine how the number was produced.
Blood testing also requires witnesses. The person who drew the blood may be needed to establish the collection procedure. The officer may be needed to explain the arrest, implied-consent process, warrant, or request for testing. The laboratory analyst may be needed to explain the testing method, instrument, quality control, and result. A number printed on paper is not self-explanatory. It must be connected to a legally obtained sample and a reliable analytical process.
Drug Blood Cases Require Additional Caution
Blood cases involving drugs or prescription medications require especially careful review. Alcohol has a relatively well-developed relationship between concentration and impairment, although individual variation remains significant. Drug cases are more complicated. The mere presence of a drug does not always establish impairment at the time of driving. Different drugs have different pharmacology, active and inactive metabolites, therapeutic ranges, tolerance issues, and detection windows.
Prescription medications create further complications. A person may lawfully take a medication and still be charged with operating while intoxicated or visibly impaired if the prosecution claims that the medication affected driving ability. But the analytical result must be interpreted in context. The defense should examine dosage, prescription history, timing, tolerance, medical conditions, observed driving, field sobriety evidence, and whether the toxicology result actually supports impairment rather than mere exposure.
How I Approach OWI Blood Test Defense
When I evaluate an OWI blood case, I begin with the legal authority for the draw. Was there a warrant? If so, did the affidavit establish probable cause, and did the warrant identify the person and evidence with sufficient particularity? If there was no warrant, what exception does the prosecution claim? Was there actual consent, implied consent, exigency, or some other theory? If implied consent was used, did the officer properly comply with MCL 257.625c and MCL 257.625a? Did the person have diabetes, hemophilia, or a condition requiring prescribed anticoagulants? Did the officer know, or should the officer have known, that the statutory blood-draw exception applied?
Only after addressing the legality of the draw do I turn to the science. I compare the time of driving, time of arrest, time of blood draw, and time of analysis. I review the chain of custody. I examine whether the sample was properly preserved. I look at whether the laboratory result is alcohol, drug, or both. I separate whole-blood forensic results from hospital serum or plasma results. I evaluate whether the prosecution is using the result for a purpose the testing method supports.
The defense of a blood test case is rarely one single issue. Sometimes the issue is an unlawful warrantless draw. Sometimes it is a defective implied-consent advisement. Sometimes it is an anticoagulant, diabetes, or hemophilia issue under MCL 257.625c(2). Sometimes it is a hospital result being treated as a forensic result. Sometimes it is a delayed draw or an unsupported retrograde extrapolation. Sometimes it is a drug result that proves presence but not impairment. Often, the defense requires several of these issues to be considered together.
Conclusion
Blood testing can be powerful evidence in a Michigan OWI case, but it should not be accepted uncritically. The fact that blood was drawn does not answer whether the draw was lawful. The fact that a laboratory reported a number does not answer whether the sample was properly collected, preserved, tested, and interpreted. The fact that a person submitted to a blood draw does not answer whether that submission was voluntary consent or mere acquiescence to asserted legal authority.
In my practice, I treat OWI blood cases as both constitutional cases and forensic science cases. The government must have lawful authority to take the blood, and it must be able to prove that the reported result is reliable and relevant to the time of driving. When either part of that showing is weak, the blood evidence may be subject to suppression, limitation, or meaningful challenge before a jury.
