Kentucky v. King (2011)

Supreme Court of the United States

Missouri v. Tyler G. McNeely

Decided April 17, 2013 – 569 U.S. 141


Justice SOTOMAYOR announced the judgment of the Court and delivered the opinion of the Court with respect to Parts I, II–A, II–B, and IV, and an opinion with respect to Part[] III, in which Justice SCALIA, Justice GINSBURG, and Justice KAGAN join.

In Schmerber v. California, 384 U.S. 757 (1966), this Court upheld a warrantless blood test of an individual arrested for driving under the influence of alcohol because the officer “might reasonably have believed that he was confronted with an emergency, in which the delay necessary to obtain a warrant, under the circumstances, threatened the destruction of evidence.” The question presented here is whether the natural metabolization of alcohol in the bloodstream presents a per se exigency that justifies an exception to the Fourth Amendment’s warrant requirement for nonconsensual blood testing in all drunk-driving cases. We conclude that it does not, and we hold, consistent with general Fourth Amendment principles, that exigency in this context must be determined case by case based on the totality of the circumstances.


While on highway patrol at approximately 2:08 a.m., a Missouri police officer stopped Tyler McNeely’s truck after observing it exceed the posted speed limit and repeatedly cross the centerline. The officer noticed several signs that McNeely was intoxicated, including McNeely’s bloodshot eyes, his slurred speech, and the smell of alcohol on his breath. McNeely acknowledged to the officer that he had consumed “a couple of beers” at a bar and he appeared unsteady on his feet when he exited the truck. After McNeely performed poorly on a battery of field-sobriety tests and declined to use a portable breath-test device to measure his blood alcohol concentration (BAC), the officer placed him under arrest.

The officer began to transport McNeely to the station house. But when McNeely indicated that he would again refuse to provide a breath sample, the officer changed course and took McNeely to a nearby hospital for blood testing. The officer did not attempt to secure a warrant. Upon arrival at the hospital, the officer asked McNeely whether he would consent to a blood test. Reading from a standard implied consent form, the officer explained to McNeely that under state law refusal to submit voluntarily to the test would lead to the immediate revocation of his driver’s license for one year and could be used against him in a future prosecution. McNeely nonetheless refused. The officer then directed a hospital lab technician to take a blood sample, and the sample was secured at approximately 2:35 a.m. Subsequent laboratory testing measured McNeely’s BAC at 0.154 percent, which was well above the legal limit of 0.08 percent. 


To determine whether a law enforcement officer faced an emergency that justified acting without a warrant, this Court looks to the totality of circumstances. We apply this “finely tuned approach” to Fourth Amendment reasonableness in this context because the police action at issue lacks “the traditional justification that … a warrant … provides.” Absent that established justification, “the fact-specific nature of the reasonableness inquiry” demands that we evaluate each case of alleged exigency based “on its own facts and circumstances.” 

The State properly recognizes that the reasonableness of a warrantless search under the exigency exception to the warrant requirement must be evaluated based on the totality of the circumstances. But the State nevertheless seeks a per se rule for blood testing in drunk-driving cases. The State contends that whenever an officer has probable cause to believe an individual has been driving under the influence of alcohol, exigent circumstances will necessarily exist because BAC evidence is inherently evanescent. As a result, the State claims that so long as the officer has probable cause and the blood test is conducted in a reasonable manner, it is categorically reasonable for law enforcement to obtain the blood sample without a warrant.

It is true that as a result of the human body’s natural metabolic processes, the alcohol level in a person’s blood begins to dissipate once the alcohol is fully absorbed and continues to decline until the alcohol is eliminated. This fact was essential to our holding in Schmerber, as we recognized that, under the circumstances, further delay in order to secure a warrant after the time spent investigating the scene of the accident and transporting the injured suspect to the hospital to receive treatment would have threatened the destruction of evidence. 

But it does not follow that we should depart from careful case-by-case assessment of exigency and adopt the categorical rule proposed by the State and its amici. In those drunk-driving investigations where police officers can reasonably obtain a warrant before a blood sample can be drawn without significantly undermining the efficacy of the search, the Fourth Amendment mandates that they do so. We do not doubt that some circumstances will make obtaining a warrant impractical such that the dissipation of alcohol from the bloodstream will support an exigency justifying a properly conducted warrantless blood test. That, however, is a reason to decide each case on its facts, as we did in Schmerber, not to accept the “considerable overgeneralization” that a per se rule would reflect. 


In short, while the natural dissipation of alcohol in the blood may support a finding of exigency in a specific case, as it did in Schmerber, it does not do so categorically. Whether a warrantless blood test of a drunk-driving suspect is reasonable must be determined case by case based on the totality of the circumstances.


We hold that in drunk-driving investigations, the natural dissipation of alcohol in the bloodstream does not constitute an exigency in every case sufficient to justify conducting a blood test without a warrant.

The judgment of the Missouri Supreme Court is affirmed.

Chief Justice ROBERTS, with whom Justice BREYER and Justice ALITO join, concurring in part and dissenting in part

[Chief Justice Roberts would have provided more robust guidance to law enforcement about precisely when warrantless nonconsensual blood draws are allowed. He wrote:

“A police officer reading this Court’s opinion would have no idea—no idea—what the Fourth Amendment requires of him, once he decides to obtain a blood sample from a drunk driving suspect who has refused a breathalyzer test. I have no quarrel with the Court’s ‘totality of the circumstances’ approach as a general matter; that is what our cases require. But the circumstances in drunk driving cases are often typical, and the Court should be able to offer guidance on how police should handle cases like the one before us.”

“In my view, the proper rule is straightforward. Our cases establish that there is an exigent circumstances exception to the warrant requirement. That exception applies when there is a compelling need to prevent the imminent destruction of important evidence, and there is no time to obtain a warrant. The natural dissipation of alcohol in the bloodstream constitutes not only the imminent but ongoing destruction of critical evidence. That would qualify as an exigent circumstance, except that there may be time to secure a warrant before blood can be drawn. If there is, an officer must seek a warrant. If an officer could reasonably conclude that there is not, the exigent circumstances exception applies by its terms, and the blood may be drawn without a warrant.”47]

Justice THOMAS, dissenting.

[Justice Thomas argued, “Because the body’s natural metabolization of alcohol inevitably destroys evidence of the crime, it constitutes an exigent circumstance. As a result, I would hold that a warrantless blood draw does not violate the Fourth Amendment.” He noted that all parties agreed about the “rapid destruction of evidence” that “occurs in every  situation where police have probable cause to arrest a drunk driver.” 

* * *

Notes, Comments, and Questions 

The Court in Birchfield v. North Dakota (2016)holds implied blood-draw consent laws that result in criminal prosecution unconstitutional.  What result if the implied consent law results in an administrative (rather than criminal) penalty?  For example, suppose a state’s implied consent law requires drivers arrested or drunk driving to consent to a breathalyzer, blood draw, saliva or urine analysis or have their license administratively revoked for one year.  See, e.g., 577.020, RSMo (2016).

In Mitchell v. Wisconsin, 139 S. Ct 2525 (2019), the Court issued a plurality opinion affirming the legality of a warrantless blood draw conducted by police after a suspect became unconscious. The plurality opinion—approved by four Justices—stated that when a driver is unconscious and cannot submit to a breath test, police may perform a blood draw under the exigent circumstances exception to the warrant requirement. The opinion relied upon Schmerber v. California, Missouri v. McNeely, and Birchfield. Justice Thomas, concurring in the judgment, would have held that the natural metabolism of alcohol by the human body always creates a per se exigency “once police have probable cause to believe the driver is drunk.” Four Justices dissented, in two separate opinions.

Notes, Comments, and Questions 

In 1984, the Court prohibited police from entering a house to arrest an apparently intoxicated man who had recently driven his car off the road and stumbled home. In 2016, the Court allowed states to demand—under threat of criminal prosecution—that motorists arrested for drunk driving submit to breath tests. The home entry was “unreasonable,” and demanding the breath test is “reasonable.”

Students might also consider, however, that the decisions could result in part on changing attitudes toward drunk driving. What was a noncriminal violation in Wisconsin in the 1980s is now punished far more severely across the nation. Mothers Against Drunk Driving, founded in 1980 after the founder’s daughter was killed in a crash involving a drunk driver, won important legislative victories beginning in 1984, when Congress acted to force states to raise their drinking ages to 21 years.48 


Icon for the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License

Criminal Procedure: Undergraduate Edition Copyright © 2022 by Christopher E. Smith is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

Share This Book