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2.12: Chapter 13 - The Warrant Requirement- Exceptions (Part 5)

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    Exigent Circumstance: Drunk Driving

    Questions concerning the scope of the “exigent circumstances” exception to the warrant requirement have arisen repeatedly in the context of drunk driving cases. These cases commonly involve a special kind of evidence—alcohol in the blood of a driver—at risk of being destroyed by the body’s metabolism.

    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.

    McNeely was charged with driving while intoxicated (DWI). He moved to suppress the results of the blood test, arguing in relevant part that, under the circumstances, taking his blood for chemical testing without first obtaining a search warrant violated his rights under the Fourth Amendment. The trial court agreed. It concluded that the exigency exception to the warrant requirement did not apply because, apart from the fact that “[a]s in all cases involving intoxication, [McNeely’s] blood alcohol was being metabolized by his liver,” there were no circumstances suggesting the officer faced an emergency in which he could not practicably obtain a warrant. On appeal, the Missouri Court of Appeals stated an intention to reverse but transferred the case directly to the Missouri Supreme Court.

    The Missouri Supreme Court affirmed. We granted certiorari to resolve a split of authority on the question whether the natural dissipation of alcohol in the bloodstream establishes a per se exigency that suffices on its own to justify an exception to the warrant requirement for nonconsensual blood testing in drunk-driving investigations. We now affirm.


    [T]he warrant requirement is subject to exceptions. “One well-recognized exception,” and the one at issue in this case, “applies when the exigencies of the situation make the needs of law enforcement so compelling that a warrantless search is objectively reasonable under the Fourth Amendment.” A variety of circumstances may give rise to an exigency sufficient to justify a warrantless search, including law enforcement’s need to provide emergency assistance to an occupant of a home, engage in “hot pursuit” of a fleeing suspect, or enter a burning building to put out a fire and investigate its cause. As is relevant here, we have also recognized that in some circumstances law enforcement officers may conduct a search without a warrant to prevent the imminent destruction of evidence. While these contexts do not necessarily involve equivalent dangers, in each a warrantless search is potentially reasonable because “there is compelling need for official action and no time to secure a warrant.”

    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.”

    Our decision in Schmerber applied this totality of the circumstances approach. In that case, the petitioner had suffered injuries in an automobile accident and was taken to the hospital. While he was there receiving treatment, a police officer arrested the petitioner for driving while under the influence of alcohol and ordered a blood test over his objection. After explaining that the warrant requirement applied generally to searches that intrude into the human body, we concluded that the warrantless blood test “in the present case” was nonetheless permissible 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.’”

    In support of that conclusion, we observed that evidence could have been lost because “the percentage of alcohol in the blood begins to diminish shortly after drinking stops, as the body functions to eliminate it from the system.” We added that “[p]articularly in a case such as this, where time had to be taken to bring the accused to a hospital and to investigate the scene of the accident, there was no time to seek out a magistrate and secure a warrant.” “Given these special facts,” we found that it was appropriate for the police to act without a warrant. We further held that the blood test at issue was a reasonable way to recover the evidence because it was highly effective, “involve[d] virtually no risk, trauma, or pain,” and was conducted in a reasonable fashion “by a physician in a hospital environment according to accepted medical practices.” And in conclusion, we noted that our judgment that there had been no Fourth Amendment violation was strictly based “on the facts of the present record.”

    Thus, our analysis in Schmerber fits comfortably within our case law applying the exigent circumstances exception. In finding the warrantless blood test reasonable in Schmerber, we considered all of the facts and circumstances of the particular case and carefully based our holding on those specific facts.


    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.

    The context of blood testing is different in critical respects from other destruction-of-evidence cases in which the police are truly confronted with a “‘now or never’” situation. In contrast to, for example, circumstances in which the suspect has control over easily disposable evidence, BAC evidence from a drunk-driving suspect naturally dissipates over time in a gradual and relatively predictable manner. Moreover, because a police officer must typically transport a drunk-driving suspect to a medical facility and obtain the assistance of someone with appropriate medical training before conducting a blood test, some delay between the time of the arrest or accident and the time of the test is inevitable regardless of whether police officers are required to obtain a warrant. This reality undermines the force of the State’s contention that we should recognize a categorical exception to the warrant requirement because BAC evidence “is actively being destroyed with every minute that passes.” Consider, for example, a situation in which the warrant process will not significantly increase the delay before the blood test is conducted because an officer can take steps to secure a warrant while the suspect is being transported to a medical facility by another officer. In such a circumstance, there would be no plausible justification for an exception to the warrant requirement.

    The State’s proposed per se rule also fails to account for advances in the 47 years since Schmerber was decided that allow for the more expeditious processing of warrant applications, particularly in contexts like drunk-driving investigations where the evidence offered to establish probable cause is simple. We by no means claim that telecommunications innovations have, will, or should eliminate all delay from the warrant-application process. But technological developments that enable police officers to secure warrants more quickly, and do so without undermining the neutral magistrate judge’s essential role as a check on police discretion, are relevant to an assessment of exigency. That is particularly so in this context, where BAC evidence is lost gradually and relatively predictably.

    Of course, there are important countervailing concerns. While experts can work backwards from the BAC at the time the sample was taken to determine the BAC at the time of the alleged offense, longer intervals may raise questions about the accuracy of the calculation. For that reason, exigent circumstances justifying a warrantless blood sample may arise in the regular course of law enforcement due to delays from the warrant application process. But adopting the State’s per se approach would improperly ignore the current and future technological developments in warrant procedures, and might well diminish the incentive for jurisdictions “to pursue progressive approaches to warrant acquisition that preserve the protections afforded by the warrant while meeting the legitimate interests of law enforcement.”

    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.


    The remaining arguments advanced in support of a per se exigency rule are unpersuasive. The State and several of its amici, including the United States, express concern that a case-by-case approach to exigency will not provide adequate guidance to law enforcement officers deciding whether to conduct a blood test of a drunk-driving suspect without a warrant. While the desire for a bright-line rule is understandable, the Fourth Amendment will not tolerate adoption of an overly broad categorical approach that would dilute the warrant requirement in a context where significant privacy interests are at stake. Moreover, a case-by-case approach is hardly unique within our Fourth Amendment jurisprudence. Numerous police actions are judged based on fact-intensive, totality of the circumstances analyses rather than according to categorical rules, including in situations that are more likely to require police officers to make difficult split-second judgments.

    Next, the State and the United States contend that the privacy interest implicated by blood draws of drunk-driving suspects is relatively minimal. That is so, they claim, both because motorists have a diminished expectation of privacy and because our cases have repeatedly indicated that blood testing is commonplace in society and typically involves “virtually no risk, trauma, or pain.”

    But the fact that people are “accorded less privacy in … automobiles because of th[e] compelling governmental need for regulation,” does not diminish a motorist’s privacy interest in preventing an agent of the government from piercing his skin. As to the nature of a blood test conducted in a medical setting by trained personnel, it is concededly less intrusive than other bodily invasions we have found unreasonable. For that reason, we have held that medically drawn blood tests are reasonable in appropriate circumstances. We have never retreated, however, from our recognition that any compelled intrusion into the human body implicates significant, constitutionally protected privacy interests.

    Finally, the State and its amici point to the compelling governmental interest in combating drunk driving and contend that prompt BAC testing, including through blood testing, is vital to pursuit of that interest. They argue that is particularly so because, in addition to laws that make it illegal to operate a motor vehicle under the influence of alcohol, all 50 States and the District of Columbia have enacted laws that make it per se unlawful to operate a motor vehicle with a BAC of over 0.08 percent. “No one can seriously dispute the magnitude of the drunken driving problem or the States’ interest in eradicating it.” Certainly we do not. While some progress has been made, drunk driving continues to exact a terrible toll on our society.

    But the general importance of the government’s interest in this area does not justify departing from the warrant requirement without showing exigent circumstances that make securing a warrant impractical in a particular case. To the extent that the State and its amici contend that applying the traditional Fourth Amendment totality-of-the-circumstances analysis to determine whether an exigency justified a warrantless search will undermine the governmental interest in preventing and prosecuting drunk-driving offenses, we are not convinced.

    States have a broad range of legal tools to enforce their drunk-driving laws and to secure BAC evidence without undertaking warrantless nonconsensual blood draws. For example, all 50 States have adopted implied consent laws that require motorists, as a condition of operating a motor vehicle within the State, to consent to BAC testing if they are arrested or otherwise detained on suspicion of a drunk-driving offense. Such laws impose significant consequences when a motorist withdraws consent; typically the motorist’s driver’s license is immediately suspended or revoked, and most States allow the motorist’s refusal to take a BAC test to be used as evidence against him in a subsequent criminal prosecution.


    The State argued before this Court that the fact that alcohol is naturally metabolized by the human body creates an exigent circumstance in every case. The State did not argue that there were exigent circumstances in this particular case because a warrant could not have been obtained within a reasonable amount of time. In his testimony before the trial court, the arresting officer did not identify any other factors that would suggest he faced an emergency or unusual delay in securing a warrant. He testified that he made no effort to obtain a search warrant before conducting the blood draw even though he was “sure” a prosecuting attorney was on call and even though he had no reason to believe that a magistrate judge would have been unavailable. The officer also acknowledged that he had obtained search warrants before taking blood samples in the past without difficulty. He explained that he elected to forgo a warrant application in this case only because he believed it was not legally necessary to obtain a warrant. Based on this testimony, the trial court concluded that there was no exigency and specifically found that, although the arrest took place in the middle of the night, “a prosecutor was readily available to apply for a search warrant and a judge was readily available to issue a warrant.”

    The Missouri Supreme Court in turn affirmed that judgment, holding first that the dissipation of alcohol did not establish a per se exigency, and second that the State could not otherwise satisfy its burden of establishing exigent circumstances. In petitioning for certiorari to this Court, the State challenged only the first holding; it did not separately contend that the warrantless blood test was reasonable regardless of whether the natural dissipation of alcohol in a suspect’s blood categorically justifies dispensing with the warrant requirement.

    Here and in its own courts the State based its case on an insistence that a driver who declines to submit to testing after being arrested for driving under the influence of alcohol is always subject to a nonconsensual blood test without any precondition for a warrant. That is incorrect.

    Although the Missouri Supreme Court referred to this case as “unquestionably a routine DWI case,” the fact that a particular drunk-driving stop is “routine” in the sense that it does not involve “‘special facts,’” such as the need for the police to attend to a car accident, does not mean a warrant is required. Other factors present in an ordinary traffic stop, such as the procedures in place for obtaining a warrant or the availability of a magistrate judge, may affect whether the police can obtain a warrant in an expeditious way and therefore may establish an exigency that permits a warrantless search. The relevant factors in determining whether a warrantless search is reasonable, including the practical problems of obtaining a warrant within a timeframe that still preserves the opportunity to obtain reliable evidence, will no doubt vary depending upon the circumstances in the case.

    Because this case was argued on the broad proposition that drunk-driving cases present a per se exigency, the arguments and the record do not provide the Court with an adequate analytic framework for a detailed discussion of all the relevant factors that can be taken into account in determining the reasonableness of acting without a warrant. It suffices to say that the metabolization of alcohol in the bloodstream and the ensuing loss of evidence are among the factors that must be considered in deciding whether a warrant is required. No doubt, given the large number of arrests for this offense in different jurisdictions nationwide, cases will arise when anticipated delays in obtaining a warrant will justify a blood test without judicial authorization, for in every case the law must be concerned that evidence is being destroyed. But that inquiry ought not to be pursued here where the question is not properly before this Court. Having rejected the sole argument presented to us challenging the Missouri Supreme Court’s decision, we affirm its judgment.

    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.”1]

    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.” He offered an evocative hypothetical:

    “Officers are watching a warehouse and observe a worker carrying bundles from the warehouse to a large bonfire and throwing them into the blaze. The officers have probable cause to believe the bundles contain marijuana. Because there is only one person carrying the bundles, the officers believe it will take hours to completely destroy the drugs. During that time the officers likely could obtain a warrant. But it is clear that the officers need not sit idly by and watch the destruction of evidence while they wait for a warrant.”]

    * * *

    The McNeely Court noted that to help enforce laws against drunk driving, states have enacted laws requiring drivers to submit to blood-alcohol tests in certain situations. Failure to submit to the test can lead to revocation of a driver’s license even if the driver is never proven in court to have driven under the influence. In Birchfield v. North Dakota, the Court considered a particularly punitive state law that—had it survived constitutional scrutiny—could have undermined the Court’s holding in McNeely.

    Supreme Court of the United States

    Danny Birchfield v. North Dakota

    Decided June 23, 2016 – 136 S. Ct. 2160

    Justice ALITO delivered the opinion of the Court.

    Drunk drivers take a grisly toll on the Nation’s roads, claiming thousands of lives, injuring many more victims, and inflicting billions of dollars in property damage every year. To fight this problem, all States have laws that prohibit motorists from driving with a blood alcohol concentration (BAC) that exceeds a specified level. But determining whether a driver’s BAC is over the legal limit requires a test, and many drivers stopped on suspicion of drunk driving would not submit to testing if given the option. So every State also has long had what are termed “implied consent laws.” These laws impose penalties on motorists who refuse to undergo testing when there is sufficient reason to believe they are violating the State’s drunk-driving laws.

    In the past, the typical penalty for noncompliance was suspension or revocation of the motorist’s license. The cases now before us involve laws that go beyond that and make it a crime for a motorist to refuse to be tested after being lawfully arrested for driving while impaired. The question presented is whether such laws violate the Fourth Amendment’s prohibition against unreasonable searches.


    Because the cooperation of the test subject is necessary when a breath test is administered and highly preferable when a blood sample is taken, the enactment of laws defining intoxication based on BAC made it necessary for States to find a way of securing such cooperation. So-called “implied consent” laws were enacted to achieve this result. They provided that cooperation with BAC testing was a condition of the privilege of driving on state roads and that the privilege would be rescinded if a suspected drunk driver refused to honor that condition. The first such law was enacted by New York in 1953, and many other States followed suit not long thereafter. In 1962, the Uniform Vehicle Code also included such a provision. Today, “all 50 States have adopted implied consent laws that require motorists, as a condition of operating a motor vehicle within the State, to consent to BAC testing if they are arrested or otherwise detained on suspicion of a drunk-driving offense.” Suspension or revocation of the motorist’s driver’s license remains the standard legal consequence of refusal. In addition, evidence of the motorist’s refusal is admitted as evidence of likely intoxication in a drunk-driving prosecution.

    In recent decades, the States and the Federal Government have toughened drunk-driving laws, and those efforts have corresponded to a dramatic decrease in alcohol-related fatalities. As of the early 1980’s, the number of annual fatalities averaged 25,000; by 2014, the most recent year for which statistics are available, the number had fallen to below 10,000. One legal change has been further lowering the BAC standard from 0.10% to 0.08%. In addition, many States now impose increased penalties for recidivists and for drivers with a BAC level that exceeds a higher threshold. In North Dakota, for example, the standard penalty for first-time drunk-driving offenders is license suspension and a fine. But an offender with a BAC of 0.16% or higher must spend at least two days in jail. In addition, the State imposes increased mandatory minimum sentences for drunk-driving recidivists.

    Many other States have taken a similar approach, but this new structure threatened to undermine the effectiveness of implied consent laws. If the penalty for driving with a greatly elevated BAC or for repeat violations exceeds the penalty for refusing to submit to testing, motorists who fear conviction for the more severely punished offenses have an incentive to reject testing. And in some States, the refusal rate is high. On average, over one-fifth of all drivers asked to submit to BAC testing in 2011 refused to do so. In North Dakota, the refusal rate for 2011 was a representative 21%.

    To combat the problem of test refusal, some States have begun to enact laws making it a crime to refuse to undergo testing. North Dakota adopted a similar law, in 2013, after a pair of drunk-driving accidents claimed the lives of an entire young family and another family’s 5- and 9-year-old boys. The Federal Government also encourages this approach as a means for overcoming the incentive that drunk drivers have to refuse a test.


    Petitioner Danny Birchfield accidentally drove his car off a North Dakota highway on October 10, 2013. A state trooper arrived and watched as Birchfield unsuccessfully tried to drive back out of the ditch in which his car was stuck. The trooper approached, caught a strong whiff of alcohol, and saw that Birchfield’s eyes were bloodshot and watery. Birchfield spoke in slurred speech and struggled to stay steady on his feet. At the trooper’s request, Birchfield agreed to take several field sobriety tests and performed poorly on each. He had trouble reciting sections of the alphabet and counting backwards in compliance with the trooper’s directions.

    Believing that Birchfield was intoxicated, the trooper informed him of his obligation under state law to agree to a BAC test. Birchfield consented to a roadside breath test. The device used for this sort of test often differs from the machines used for breath tests administered in a police station and is intended to provide a preliminary assessment of the driver’s BAC. Because the reliability of these preliminary or screening breath tests varies, many jurisdictions do not permit their numerical results to be admitted in a drunk-driving trial as evidence of a driver’s BAC. In North Dakota, results from this type of test are “used only for determining whether or not a further test shall be given.” In Birchfield’s case, the screening test estimated that his BAC was 0.254%, more than three times the legal limit of 0.08%.

    The state trooper arrested Birchfield for driving while impaired, gave the usual Miranda warnings, again advised him of his obligation under North Dakota law to undergo BAC testing, and informed him, as state law requires that refusing to take the test would expose him to criminal penalties. In addition to mandatory addiction treatment, sentences range from a mandatory fine of $500 (for first-time offenders) to fines of at least $2,000 and imprisonment of at least one year and one day (for serial offenders). These criminal penalties apply to blood, breath, and urine test refusals alike.

    Although faced with the prospect of prosecution under this law, Birchfield refused to let his blood be drawn. Just three months before, Birchfield had received a citation for driving under the influence, and he ultimately pleaded guilty to that offense. This time he also pleaded guilty—to a misdemeanor violation of the refusal statute—but his plea was a conditional one: while Birchfield admitted refusing the blood test, he argued that the Fourth Amendment prohibited criminalizing his refusal to submit to the test. The State District Court rejected this argument and imposed a sentence that accounted for his prior conviction. The sentence included 30 days in jail (20 of which were suspended and 10 of which had already been served), 1 year of unsupervised probation, $1,750 in fine and fees, and mandatory participation in a sobriety program and in a substance abuse evaluation.

    On appeal, the North Dakota Supreme Court affirmed. The court found support for the test refusal statute in this Court’s McNeely plurality opinion, which had spoken favorably about “acceptable ‘legal tools’ with ‘significant consequences’ for refusing to submit to testing.”

    We granted certiorari in order to decide whether motorists lawfully arrested for drunk driving may be convicted of a crime or otherwise penalized for refusing to take a warrantless test measuring the alcohol in their bloodstream.


    [S]uccess for [] petitioner[] depends on the proposition that the criminal law ordinarily may not compel a motorist to submit to the taking of a blood sample or to a breath test unless a warrant authorizing such testing is issued by a magistrate. If, on the other hand, such warrantless searches comport with the Fourth Amendment, it follows that a State may criminalize the refusal to comply with a demand to submit to the required testing, just as a State may make it a crime for a person to obstruct the execution of a valid search warrant. And by the same token, if such warrantless searches are constitutional, there is no obstacle under federal law to the admission of the results that they yield in either a criminal prosecution or a civil or administrative proceeding. We therefore begin by considering whether the searches demanded in these cases were consistent with the Fourth Amendment.


    The [Fourth] Amendment [] prohibits “unreasonable searches,” and our cases establish that the taking of a blood sample or the administration of a breath test is a search. The question, then, is whether the warrantless searches at issue here were reasonable. “[T]he text of the Fourth Amendment does not specify when a search warrant must be obtained.” But “this Court has inferred that a warrant must [usually] be secured.” This usual requirement, however, is subject to a number of exceptions.

    We have previously had occasion to examine whether one such exception—for “exigent circumstances”—applies in drunk-driving investigations. In Schmerber v. California, we held that drunk driving may present such an exigency. More recently, though, we have held that the natural dissipation of alcohol from the bloodstream does not always constitute an exigency justifying the warrantless taking of a blood sample. While emphasizing that the exigent-circumstances exception must be applied on a case-by-case basis, the [Missouri v.] McNeely Court noted that other exceptions to the warrant requirement “apply categorically” rather than in a “case-specific” fashion. One of these, as the McNeely opinion recognized, is the long-established rule that a warrantless search may be conducted incident to a lawful arrest. But the Court pointedly did not address any potential justification for warrantless testing of drunk-driving suspects except for the exception “at issue in th[e] case,” namely, the exception for exigent circumstances.

    In the [] case[] now before us, the driver[] w[as] [] told that [he was] required to submit to a search after being placed under arrest for drunk driving. We therefore consider how the search-incident-to-arrest doctrine applies to breath and blood tests incident to such arrests.


    Blood and breath tests to measure blood alcohol concentration are not as new as searches of cell phones, but here, as in Riley [v. California], the founding era does not provide any definitive guidance as to whether they should be allowed incident to arrest. Lacking such guidance, we engage in the same mode of analysis as in Riley: we examine “the degree to which [they] intrud[e] upon an individual’s privacy and … the degree to which [they are] needed for the promotion of legitimate governmental interests.’” We begin by considering the impact of breath and blood tests on individual privacy interests, and we will discuss each type of test in turn.

    Years ago we said that breath tests do not “implicat[e] significant privacy concerns.” That remains so today. First, the physical intrusion is almost negligible. Breath tests “do not require piercing the skin” and entail “a minimum of inconvenience.” The effort is no more demanding than blowing up a party balloon.

    In prior cases, we have upheld warrantless searches involving physical intrusions that were at least as significant as that entailed in the administration of a breath test. Just recently we described the process of collecting a DNA sample by rubbing a swab on the inside of a person’s cheek as a “negligible” intrusion. We have also upheld scraping underneath a suspect’s fingernails to find evidence of a crime, calling that a “very limited intrusion.” A breath test is no more intrusive than either of these procedures.

    Second, breath tests are capable of revealing only one bit of information, the amount of alcohol in the subject’s breath. In this respect, they contrast sharply with the sample of cells collected by the swab in Maryland v. King [, 569 U.S. 435 (2013)]. Although the DNA obtained under the law at issue in that case could lawfully be used only for identification purposes, the process put into the possession of law enforcement authorities a sample from which a wealth of additional, highly personal information could potentially be obtained. A breath test, by contrast, results in a BAC reading on a machine, nothing more. No sample of anything is left in the possession of the police.

    Finally, participation in a breath test is not an experience that is likely to cause any great enhancement in the embarrassment that is inherent in any arrest. The act of blowing into a straw is not inherently embarrassing, nor are evidentiary breath tests administered in a manner that causes embarrassment. Again, such tests are normally administered in private at a police station, in a patrol car, or in a mobile testing facility, out of public view. Moreover, once placed under arrest, the individual’s expectation of privacy is necessarily diminished. For all these reasons, “[a] breath test does not “implicat[e] significant privacy concerns.”

    Blood tests are a different matter. They “require piercing the skin” and extract a part of the subject’s body. And while humans exhale air from their lungs many times per minute, humans do not continually shed blood. It is true, of course, that people voluntarily submit to the taking of blood samples as part of a physical examination, and the process involves little pain or risk. Nevertheless, for many, the process is not one they relish. It is significantly more intrusive than blowing into a tube. Perhaps that is why many States’ implied consent laws specifically prescribe that breath tests be administered in the usual drunk-driving case instead of blood tests or give motorists a measure of choice over which test to take.

    In addition, a blood test, unlike a breath test, places in the hands of law enforcement authorities a sample that can be preserved and from which it is possible to extract information beyond a simple BAC reading. Even if the law enforcement agency is precluded from testing the blood for any purpose other than to measure BAC, the potential remains and may result in anxiety for the person tested.

    Having assessed the impact of breath and blood testing on privacy interests, we now look to the States’ asserted need to obtain BAC readings for persons arrested for drunk driving.

    The States and the Federal Government have a “paramount interest … in preserving the safety of … public highways.” Although the number of deaths and injuries caused by motor vehicle accidents has declined over the years, the statistics are still staggering.

    Alcohol consumption is a leading cause of traffic fatalities and injuries. During the past decade, annual fatalities in drunk-driving accidents ranged from 13,582 deaths in 2005 to 9,865 deaths in 2011. The most recent data report a total of 9,967 such fatalities in 2014—on average, one death every 53 minutes. Our cases have long recognized the “carnage” and “slaughter” caused by drunk drivers.

    To deter potential drunk drivers and thereby reduce alcohol-related injuries, the States and the Federal Government have taken the series of steps that we recounted earlier. The law[] at issue in the present cases—which make it a crime to refuse to submit to a BAC test—are designed to provide an incentive to cooperate in such cases, and we conclude that they serve a very important function.

    Petitioner[] contend[s] that the States and the Federal Government could combat drunk driving in other ways that do not have the same impact on personal privacy. [His] argument[] [is] unconvincing.

    The chief argument on this score is that an officer making an arrest for drunk driving should not be allowed to administer a BAC test unless the officer procures a search warrant or could not do so in time to obtain usable test results.

    This argument contravenes our decisions holding that the legality of a search incident to arrest must be judged on the basis of categorical rules.

    Petitioners next suggest[s] that requiring a warrant for BAC testing in every case in which a motorist is arrested for drunk driving would not impose any great burden on the police or the courts. But of course the same argument could be made about searching through objects found on the arrestee’s possession, which our cases permit even in the absence of a warrant. What about the cigarette package in [United States v.] Robinson? What if a motorist arrested for drunk driving has a flask in his pocket? What if a motorist arrested for driving while under the influence of marijuana has what appears to be a marijuana cigarette on his person? What about an unmarked bottle of pills?

    If a search warrant were required for every search incident to arrest that does not involve exigent circumstances, the courts would be swamped. And even if we arbitrarily singled out BAC tests incident to arrest for this special treatment, the impact on the courts would be considerable. The number of arrests every year for driving under the influence is enormous—more than 1.1 million in 2014. Particularly in sparsely populated areas, it would be no small task for courts to field a large new influx of warrant applications that could come on any day of the year and at any hour. In many jurisdictions, judicial officers have the authority to issue warrants only within their own districts, and in rural areas, some districts may have only a small number of judicial officers.

    North Dakota, for instance, has only 51 state district judges spread across eight judicial districts. Those judges are assisted by 31 magistrates, and there are no magistrates in 20 of the State’s 53 counties. At any given location in the State, then, relatively few state officials have authority to issue search warrants. Yet the State, with a population of roughly 740,000, sees nearly 7,000 drunk-driving arrests each year. With a small number of judicial officers authorized to issue warrants in some parts of the State, the burden of fielding BAC warrant applications 24 hours per day, 365 days of the year would not be the light burden that petitioner[] suggest[s].

    In light of this burden and our prior search-incident-to-arrest precedents, petitioner[] would at a minimum have to show some special need for warrants for BAC testing. It is therefore appropriate to consider the benefits that such applications would provide. Search warrants protect privacy in two main ways. First, they ensure that a search is not carried out unless a neutral magistrate makes an independent determination that there is probable cause to believe that evidence will be found. Second, if the magistrate finds probable cause, the warrant limits the intrusion on privacy by specifying the scope of the search—that is, the area that can be searched and the items that can be sought.

    How well would these functions be performed by the warrant applications that petitioners propose? In order to persuade a magistrate that there is probable cause for a search warrant, the officer would typically recite the same facts that led the officer to find that there was probable cause for arrest, namely, that there is probable cause to believe that a BAC test will reveal that the motorist’s blood alcohol level is over the limit. [T]he facts that establish probable cause are largely the same from one drunk-driving stop to the next and consist largely of the officer’s own characterization of his or her observations—for example, that there was a strong odor of alcohol, that the motorist wobbled when attempting to stand, that the motorist paused when reciting the alphabet or counting backwards, and so on. A magistrate would be in a poor position to challenge such characterizations.

    As for the second function served by search warrants—delineating the scope of a search—the warrants in question here would not serve that function at all. In every case the scope of the warrant would simply be a BAC test of the arrestee. For these reasons, requiring the police to obtain a warrant in every case would impose a substantial burden but no commensurate benefit.

    Having assessed the effect of BAC tests on privacy interests and the need for such tests, we conclude that the Fourth Amendment permits warrantless breath tests incident to arrests for drunk driving. The impact of breath tests on privacy is slight, and the need for BAC testing is great.

    We reach a different conclusion with respect to blood tests. Blood tests are significantly more intrusive, and their reasonableness must be judged in light of the availability of the less invasive alternative of a breath test. Respondents have offered no satisfactory justification for demanding the more intrusive alternative without a warrant.

    Neither respondents nor their amici dispute the effectiveness of breath tests in measuring BAC. Breath tests have been in common use for many years. Their results are admissible in court and are widely credited by juries, and respondents do not dispute their accuracy or utility. What, then, is the justification for warrantless blood tests?

    One advantage of blood tests is their ability to detect not just alcohol but also other substances that can impair a driver’s ability to operate a car safely. A breath test cannot do this, but police have other measures at their disposal when they have reason to believe that a motorist may be under the influence of some other substance (for example, if a breath test indicates that a clearly impaired motorist has little if any alcohol in his blood). Nothing prevents the police from seeking a warrant for a blood test when there is sufficient time to do so in the particular circumstances or from relying on the exigent circumstances exception to the warrant requirement when there is not.

    A blood test also requires less driver participation than a breath test. In order for a technician to take a blood sample, all that is needed is for the subject to remain still, either voluntarily or by being immobilized. Thus, it is possible to extract a blood sample from a subject who forcibly resists, but many States reasonably prefer not to take this step. North Dakota, for example, tells us that it generally opposes this practice because of the risk of dangerous altercations between police officers and arrestees in rural areas where the arresting officer may not have backup. Under current North Dakota law, only in cases involving an accident that results in death or serious injury may blood be taken from arrestees who resist.

    It is true that a blood test, unlike a breath test, may be administered to a person who is unconscious (perhaps as a result of a crash) or who is unable to do what is needed to take a breath test due to profound intoxication or injuries. But we have no reason to believe that such situations are common in drunk-driving arrests, and when they arise, the police may apply for a warrant if need be.

    A breath test may also be ineffective if an arrestee deliberately attempts to prevent an accurate reading by failing to blow into the tube for the requisite length of time or with the necessary force. But courts have held that such conduct qualifies as a refusal to undergo testing and it may be prosecuted as such. And again, a warrant for a blood test may be sought.

    Because breath tests are significantly less intrusive than blood tests and in most cases amply serve law enforcement interests, we conclude that a breath test, but not a blood test, may be administered as a search incident to a lawful arrest for drunk driving. As in all cases involving reasonable searches incident to arrest, a warrant is not needed in this situation.


    Having concluded that the search incident to arrest doctrine does not justify the warrantless taking of a blood sample, we must address respondents’ alternative argument that such tests are justified based on the driver’s legally implied consent to submit to them. It is well established that a search is reasonable when the subject consents, and that sometimes consent to a search need not be express but may be fairly inferred from context. Our prior opinions have referred approvingly to the general concept of implied-consent laws that impose civil penalties and evidentiary consequences on motorists who refuse to comply. Petitioner[] do[es] not question the constitutionality of those laws, and nothing we say here should be read to cast doubt on them.

    It is another matter, however, for a State not only to insist upon an intrusive blood test, but also to impose criminal penalties on the refusal to submit to such a test. There must be a limit to the consequences to which motorists may be deemed to have consented by virtue of a decision to drive on public roads.

    Respondents and their amici all but concede this point. North Dakota emphasizes that its law makes refusal a misdemeanor and suggests that laws punishing refusal more severely would present a different issue. Borrowing from our Fifth Amendment jurisprudence, the United States suggests that motorists could be deemed to have consented to only those conditions that are “reasonable” in that they have a “nexus” to the privilege of driving and entail penalties that are proportional to severity of the violation. But in the Fourth Amendment setting, this standard does not differ in substance from the one that we apply, since reasonableness is always the touchstone of Fourth Amendment analysis. And applying this standard, we conclude that motorists cannot be deemed to have consented to submit to a blood test on pain of committing a criminal offense.


    Our remaining task is to apply our legal conclusions to the [] case[] before us.

    Petitioner Birchfield was criminally prosecuted for refusing a warrantless blood draw, and therefore the search he refused cannot be justified as a search incident to his arrest or on the basis of implied consent. There is no indication in the record or briefing that a breath test would have failed to satisfy the State’s interests in acquiring evidence to enforce its drunk-driving laws against Birchfield. And North Dakota has not presented any case-specific information to suggest that the exigent circumstances exception would have justified a warrantless search. Unable to see any other basis on which to justify a warrantless test of Birchfield’s blood, we conclude that Birchfield was threatened with an unlawful search and that the judgment affirming his conviction must be reversed.

    We accordingly reverse the judgment of the North Dakota Supreme Court and remand the case for further proceedings not inconsistent with this opinion.

    Justice THOMAS, concurring in judgment in part and dissenting in part.

    The compromise the Court reaches today is not a good one. By deciding that some (but not all) warrantless tests revealing the blood alcohol concentration (BAC) of an arrested driver are constitutional, the Court contorts the search-incident-to-arrest exception to the Fourth Amendment’s warrant requirement. The far simpler answer to the question presented is the one rejected in Missouri v. McNeely. Here, the tests revealing the BAC of a driver suspected of driving drunk are constitutional under the exigent-circumstances exception to the warrant requirement.


    Today’s decision chips away at a well-established exception to the warrant requirement. Until recently, we have admonished that “[a] police officer’s determination as to how and where to search the person of a suspect whom he has arrested is necessarily a quick ad hoc judgment which the Fourth Amendment does not require to be broken down in each instance into an analysis of each step in the search.” Under our precedents, a search incident to lawful arrest “require[d] no additional justification.” Not until the recent decision in Riley v. California, did the Court begin to retreat from this categorical approach because it feared that the search at issue, the “search of the information on a cell phone,” bore “little resemblance to the type of brief physical search” contemplated by this Court’s past search-incident-to-arrest decisions. I joined Riley, however, because the Court resisted the temptation to permit searches of some kinds of cellphone data and not others and instead asked more generally whether that entire “category of effects” was searchable without a warrant.

    Today’s decision begins where Riley left off. The Court purports to apply Robinson but further departs from its categorical approach by holding that warrantless breath tests to prevent the destruction of BAC evidence are constitutional searches incident to arrest, but warrantless blood tests are not. That hairsplitting makes little sense. Either the search-incident-to-arrest exception permits bodily searches to prevent the destruction of BAC evidence, or it does not.

    The Court justifies its result—an arbitrary line in the sand between blood and breath tests—by balancing the invasiveness of the particular type of search against the government’s reasons for the search. Such case-by-case balancing is bad for the People, who “through ratification, have already weighed the policy tradeoffs that constitutional rights entail.” It is also bad for law enforcement officers, who depend on predictable rules to do their job, as Members of this Court have exhorted in the past.

    Today’s application of the search-incident-to-arrest exception is bound to cause confusion in the lower courts. The Court’s choice to allow some (but not all) BAC searches is undeniably appealing, for it both reins in the pernicious problem of drunk driving and also purports to preserve some Fourth Amendment protections. But that compromise has little support under this Court’s existing precedents.


    The better (and far simpler) way to resolve these cases is by applying the per se rule that I proposed in McNeely. Under that approach, both warrantless breath and blood tests are constitutional because “the natural metabolization of [BAC] creates an exigency once police have probable cause to believe the driver is drunk. It naturally follows that police may conduct a search in these circumstances.”

    Today’s decision rejects McNeely’s arbitrary distinction between the destruction of evidence generally and the destruction of BAC evidence. But only for searches incident to arrest. The Court declares that such a distinction “between an arrestee’s active destruction of evidence and the loss of evidence due to a natural process makes little sense.” I agree. But it also “makes little sense” for the Court to reject McNeely’s arbitrary distinction only for searches incident to arrest and not also for exigent-circumstances searches when both are justified by identical concerns about the destruction of the same evidence. McNeely’s distinction is no less arbitrary for searches justified by exigent circumstances than those justified by search incident to arrest.

    The Court was wrong in McNeely, and today’s compromise is perhaps an inevitable consequence of that error. Both searches contemplated by the state laws at issue in these cases would be constitutional under the exigent-circumstances exception to the warrant requirement. I respectfully concur in the judgment in part and dissent in part.

    Notes, Comments, and Questions

    The Court in Birchfield 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 for 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.

    Like the preceding cases, Welsh v. Wisconsin involves police investigation of drunk driving and an argument about whether the exigent circumstances exception justifies certain police activity. The key difference here is that instead of seeking to take a suspect’s blood, the police in Welsh sought to enter his home to arrest him. In addition, this case illustrates the far more relaxed attitude toward drunk driving that was common among judges and legislators in the 1980s.

    Supreme Court of the United States

    Edward G. Welsh v. Wisconsin

    Decided May 15, 1984 – 466 U.S. 740

    Justice BRENNAN delivered the opinion of the Court.

    Payton v. New York, 445 U.S. 573 (1980), held that, absent probable cause and exigent circumstances, warrantless arrests in the home are prohibited by the Fourth Amendment. But the Court in that case explicitly refused “to consider the sort of emergency or dangerous situation, described in our cases as ‘exigent circumstances,’ that would justify a warrantless entry into a home for the purpose of either arrest or search.” Certiorari was granted in this case to decide at least one aspect of the unresolved question: whether, and if so under what circumstances, the Fourth Amendment prohibits the police from making a warrantless night entry of a person’s home in order to arrest him for a nonjailable traffic offense.


    Shortly before 9 o’clock on the rainy night of April 24, 1978, a lone witness, Randy Jablonic, observed a car being driven erratically. After changing speeds and veering from side to side, the car eventually swerved off the road and came to a stop in an open field. No damage to any person or property occurred. Concerned about the driver and fearing that the car would get back on the highway, Jablonic drove his truck up behind the car so as to block it from returning to the road. Another passerby also stopped at the scene, and Jablonic asked her to call the police. Before the police arrived, however, the driver of the car emerged from his vehicle, approached Jablonic’s truck, and asked Jablonic for a ride home. Jablonic instead suggested that they wait for assistance in removing or repairing the car. Ignoring Jablonic’s suggestion, the driver walked away from the scene.

    A few minutes later, the police arrived and questioned Jablonic. He told one officer what he had seen, specifically noting that the driver was either very inebriated or very sick. The officer checked the motor vehicle registration of the abandoned car and learned that it was registered to the petitioner, Edward G. Welsh. In addition, the officer noted that the petitioner’s residence was a short distance from the scene, and therefore easily within walking distance.

    Without securing any type of warrant, the police proceeded to the petitioner’s home, arriving about 9 p.m. When the petitioner’s stepdaughter answered the door, the police gained entry into the house.2 Proceeding upstairs to the petitioner’s bedroom, they found him lying naked in bed. At this point, the petitioner was placed under arrest for driving or operating a motor vehicle while under the influence of an intoxicant. The petitioner was taken to the police station, where he refused to submit to a breath-analysis test.


    As a result of these events, the petitioner was subjected to two separate but related proceedings: one concerning his refusal to submit to a breath test and the other involving the alleged code violation for driving while intoxicated. Under the Wisconsin Vehicle Code in effect in April 1978, one arrested for driving while intoxicated [] could be requested by a law enforcement officer to provide breath, blood, or urine samples for the purpose of determining the presence or quantity of alcohol. If such a request was made, the arrestee was required to submit to the appropriate testing or risk a revocation of operating privileges … for 60 days.


    [T]he State filed a criminal complaint against the petitioner for driving while intoxicated. The petitioner responded by filing a motion to dismiss the complaint, relying on his contention that the underlying arrest was invalid. After receiving evidence at a hearing on this motion in July 1980, the trial court concluded that the criminal complaint would not be dismissed because the existence of both probable cause and exigent circumstances justified the warrantless arrest. [T]he appellate court concluded that the warrantless arrest of the petitioner in his home violated the Fourth Amendment because the State, although demonstrating probable cause to arrest, had not established the existence of exigent circumstances. The Supreme Court of Wisconsin in turn reversed the Court of Appeals. Because of the important Fourth Amendment implications of the decision below, we granted certiorari.


    [T]he Court decided in Payton v. New York that warrantless felony arrests in the home are prohibited by the Fourth Amendment, absent probable cause and exigent circumstances. At the same time, the Court declined to consider the scope of any exception for exigent circumstances that might justify warrantless home arrests, thereby leaving to the lower courts the initial application of the exigent-circumstances exception. Prior decisions of this Court, however, have emphasized that exceptions to the warrant requirement are “few in number and carefully delineated” and that the police bear a heavy burden when attempting to demonstrate an urgent need that might justify warrantless searches or arrests. Indeed, the Court has recognized only a few such emergency conditions.

    Our hesitation in finding exigent circumstances, especially when warrantless arrests in the home are at issue, is particularly appropriate when the underlying offense for which there is probable cause to arrest is relatively minor. Before agents of the government may invade the sanctity of the home, the burden is on the government to demonstrate exigent circumstances that overcome the presumption of unreasonableness that attaches to all warrantless home entries. When the government’s interest is only to arrest for a minor offense, that presumption of unreasonableness is difficult to rebut, and the government usually should be allowed to make such arrests only with a warrant issued upon probable cause by a neutral and detached magistrate.

    We [] conclude that the common-sense approach utilized by most lower courts is required by the Fourth Amendment prohibition on “unreasonable searches and seizures,” and hold that an important factor to be considered when determining whether any exigency exists is the gravity of the underlying offense for which the arrest is being made. Moreover, although no exigency is created simply because there is probable cause to believe that a serious crime has been committed, application of the exigent-circumstances exception in the context of a home entry should rarely be sanctioned when there is probable cause to believe that only a minor offense, such as the kind at issue in this case, has been committed.

    Application of this principle to the facts of the present case is relatively straightforward. The petitioner was arrested in the privacy of his own bedroom for a noncriminal, traffic offense. The State attempts to justify the arrest by relying on the hot-pursuit doctrine, on the threat to public safety, and on the need to preserve evidence of the petitioner’s blood-alcohol level. On the facts of this case, however, the claim of hot pursuit is unconvincing because there was no immediate or continuous pursuit of the petitioner from the scene of a crime. Moreover, because the petitioner had already arrived home, and had abandoned his car at the scene of the accident, there was little remaining threat to the public safety. Hence, the only potential emergency claimed by the State was the need to ascertain the petitioner’s blood-alcohol level.

    Even assuming, however, that the underlying facts would support a finding of this exigent circumstance, mere similarity to other cases involving the imminent destruction of evidence is not sufficient. The State of Wisconsin has chosen to classify the first offense for driving while intoxicated as a noncriminal, civil forfeiture offense for which no imprisonment is possible. This is the best indication of the State’s interest in precipitating an arrest, and is one that can be easily identified both by the courts and by officers faced with a decision to arrest. Given this expression of the State’s interest, a warrantless home arrest cannot be upheld simply because evidence of the petitioner’s blood-alcohol level might have dissipated while the police obtained a warrant. To allow a warrantless home entry on these facts would be to approve unreasonable police behavior that the principles of the Fourth Amendment will not sanction.


    The Supreme Court of Wisconsin let stand a warrantless, nighttime entry into the petitioner’s home to arrest him for a civil traffic offense. Such an arrest, however, is clearly prohibited by the special protection afforded the individual in his home by the Fourth Amendment. The petitioner’s arrest was therefore invalid, the judgment of the Supreme Court of Wisconsin is vacated, and the case is remanded for further proceedings not inconsistent with this opinion.

    Justice BLACKMUN, concurring.

    I join the Court’s opinion but add a personal observation.

    I yield to no one in my profound personal concern about the unwillingness of our national consciousness to face up to—and to do something about—the continuing slaughter upon our Nation’s highways, a good percentage of which is due to drivers who are drunk or semi-incapacitated because of alcohol or drug ingestion. I have spoken in these Reports to this point before. And it is amazing to me that one of our great States—one which, by its highway signs, proclaims to be diligent and emphatic in its prosecution of the drunken driver—still classifies driving while intoxicated as a civil violation that allows only a money forfeiture of not more than $300 so long as it is a first offense. The State, like the indulgent parent, hesitates to discipline the spoiled child very much, even though the child is engaging in an act that is dangerous to others who are law abiding and helpless in the face of the child’s act. Our personal convenience still weighs heavily in the balance, and the highway deaths and injuries continue. But if Wisconsin and other States choose by legislation thus to regulate their penalty structure, there is, unfortunately, nothing in the United States Constitution that says they may not do so.

    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.”

    Perhaps the results can be explained by Fourth Amendment doctrine that has remained constant since 1791. 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. The position articulated by Justice Blackmun in his dissent in Welsh, in which he chastised Wisconsin for its lax treatment of drunken drivers, has won widespread appeal among lawmakers, both those on the bench and those in legislatures. 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.3