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2.14: Chapter 15 - The Warrant Requirement- Exceptions (Part 7)

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    Warrant Exception: Checkpoints

    In this chapter, we consider two situations in which the Court has authorized warrantless searches: (1) checkpoints, generally aimed at protecting the public from intoxicated drivers, and (2) “protective sweeps” that police may conduct in association with an arrest. Note that sweeps are distinct from searches incident to lawful arrest and are governed by different rules.

    We begin with vehicle checkpoints. Checkpoints involve stopping cars randomly—or otherwise selecting cars to stop without any specific reason to believe that the drivers are intoxicated or otherwise breaking the law or transporting items subject to seizure. Accordingly, vehicle checkpoints can be permissible only if the Court allows police seizures of persons and property without even reasonable suspicion, much less probable cause. The question is whether such seizures are “reasonable” under the Fourth Amendment.

    Supreme Court of the United States

    Michigan State Police v. Rick Sitz

    Decided June 14, 1990 – 496 U.S. 444

    Chief Justice REHNQUIST delivered the opinion of the Court.

    This case poses the question whether a State’s use of highway sobriety checkpoints violates the Fourth and Fourteenth Amendments to the United States Constitution. We hold that it does not and therefore reverse the contrary holding of the Court of Appeals of Michigan.

    Petitioners, the Michigan Department of State Police and its director, established a sobriety checkpoint pilot program in early 1986. The director appointed a Sobriety Checkpoint Advisory Committee comprising representatives of the State Police force, local police forces, state prosecutors, and the University of Michigan Transportation Research Institute. Pursuant to its charge, the advisory committee created guidelines setting forth procedures governing checkpoint operations, site selection, and publicity.

    Under the guidelines, checkpoints would be set up at selected sites along state roads. All vehicles passing through a checkpoint would be stopped and their drivers briefly examined for signs of intoxication. In cases where a checkpoint officer detected signs of intoxication, the motorist would be directed to a location out of the traffic flow where an officer would check the motorist’s driver’s license and car registration and, if warranted, conduct further sobriety tests. Should the field tests and the officer’s observations suggest that the driver was intoxicated, an arrest would be made. All other drivers would be permitted to resume their journey immediately.

    The first—and to date the only—sobriety checkpoint operated under the program was conducted in Saginaw County with the assistance of the Saginaw County Sheriff’s Department. During the 75-minute duration of the checkpoint’s operation, 126 vehicles passed through the checkpoint. The average delay for each vehicle was approximately 25 seconds. Two drivers were detained for field sobriety testing, and one of the two was arrested for driving under the influence of alcohol. A third driver who drove through without stopping was pulled over by an officer in an observation vehicle and arrested for driving under the influence.

    On the day before the operation of the Saginaw County checkpoint, respondents filed a complaint in the Circuit Court of Wayne County seeking declaratory and injunctive relief from potential subjection to the checkpoints. Each of the respondents “is a licensed driver in the State of Michigan … who regularly travels throughout the State in his automobile.” During pretrial proceedings, petitioners agreed to delay further implementation of the checkpoint program pending the outcome of this litigation.

    After the trial, at which the court heard extensive testimony concerning, inter alia, the “effectiveness” of highway sobriety checkpoint programs, the court ruled that the Michigan program violated the Fourth Amendment. On appeal, the Michigan Court of Appeals affirmed the holding. After the Michigan Supreme Court denied petitioners’ application for leave to appeal, we granted certiorari.

    Petitioners concede, correctly in our view, that a Fourth Amendment “seizure” occurs when a vehicle is stopped at a checkpoint. The question thus becomes whether such seizures are “reasonable” under the Fourth Amendment.

    It is important to recognize what our inquiry is not about. No allegations are before us of unreasonable treatment of any person after an actual detention at a particular checkpoint. As pursued in the lower courts, the instant action challenges only the use of sobriety checkpoints generally. We address only the initial stop of each motorist passing through a checkpoint and the associated preliminary questioning and observation by checkpoint officers. Detention of particular motorists for more extensive field sobriety testing may require satisfaction of an individualized suspicion standard.

    No one can seriously dispute the magnitude of the drunken driving problem or the States’ interest in eradicating it. Media reports of alcohol-related death and mutilation on the Nation’s roads are legion. The anecdotal is confirmed by the statistical. “Drunk drivers cause an annual death toll of over 25,000 and in the same time span cause nearly one million personal injuries and more than five billion dollars in property damage.”

    Conversely, the weight bearing on the other scale—the measure of the intrusion on motorists stopped briefly at sobriety checkpoints—is slight. We reached a similar conclusion as to the intrusion on motorists subjected to a brief stop at a highway checkpoint for detecting illegal aliens. We see virtually no difference between the levels of intrusion on law-abiding motorists from the brief stops necessary to the effectuation of these two types of checkpoints, which to the average motorist would seem identical save for the nature of the questions the checkpoint officers might ask. The trial court and the Court of Appeals, thus, accurately gauged the “objective” intrusion, measured by the duration of the seizure and the intensity of the investigation, as minimal.

    With respect to what it perceived to be the “subjective” intrusion on motorists, however, the Court of Appeals found such intrusion substantial. The court first affirmed the trial court’s finding that the guidelines governing checkpoint operation minimize the discretion of the officers on the scene. But the court also agreed with the trial court’s conclusion that the checkpoints have the potential to generate fear and surprise in motorists. This was so because the record failed to demonstrate that approaching motorists would be aware of their option to make U-turns or turnoffs to avoid the checkpoints. On that basis, the court deemed the subjective intrusion from the checkpoints unreasonable.

    We believe the Michigan courts misread our cases concerning the degree of “subjective intrusion” and the potential for generating fear and surprise. The “fear and surprise” to be considered are not the natural fear of one who has been drinking over the prospect of being stopped at a sobriety checkpoint but, rather, the fear and surprise engendered in law-abiding motorists by the nature of the stop. This was made clear in Martinez-Fuerte.

    Here, checkpoints are selected pursuant to the guidelines, and uniformed police officers stop every approaching vehicle. The intrusion resulting from the brief stop at the sobriety checkpoint is for constitutional purposes indistinguishable from the checkpoint stops we upheld in Martinez-Fuerte.

    In sum, the balance of the State’s interest in preventing drunken driving, the extent to which this system can reasonably be said to advance that interest, and the degree of intrusion upon individual motorists who are briefly stopped, weighs in favor of the state program. We therefore hold that it is consistent with the Fourth Amendment. The judgment of the Michigan Court of Appeals is accordingly reversed, and the cause is remanded for further proceedings not inconsistent with this opinion.

    Justice BRENNAN, with whom Justice MARSHALL joins, dissenting.

    Today, the Court rejects a Fourth Amendment challenge to a sobriety checkpoint policy in which police stop all cars and inspect all drivers for signs of intoxication without any individualized suspicion that a specific driver is intoxicated. The Court does so by balancing “the State’s interest in preventing drunken driving, the extent to which this system can reasonably be said to advance that interest, and the degree of intrusion upon individual motorists who are briefly stopped.” [T]he Court misapplies that test by undervaluing the nature of the intrusion and exaggerating the law enforcement need to use the roadblocks to prevent drunken driving.

    I do not dispute the immense social cost caused by drunken drivers, nor do I slight the government’s efforts to prevent such tragic losses. Indeed, I would hazard a guess that today’s opinion will be received favorably by a majority of our society, who would willingly suffer the minimal intrusion of a sobriety checkpoint stop in order to prevent drunken driving. But consensus that a particular law enforcement technique serves a laudable purpose has never been the touchstone of constitutional analysis.

    “The Fourth Amendment was designed not merely to protect against official intrusions whose social utility was less as measured by some ‘balancing test’ than its intrusion on individual privacy; it was designed in addition to grant the individual a zone of privacy whose protections could be breached only where the ‘reasonable’ requirements of the probable-cause standard were met. Moved by whatever momentary evil has aroused their fears, officials—perhaps even supported by a majority of citizens—may be tempted to conduct searches that sacrifice the liberty of each citizen to assuage the perceived evil. But the Fourth Amendment rests on the principle that a true balance between the individual and society depends on the recognition of ‘the right to be let alone—the most comprehensive of rights and the right most valued by civilized men.’”

    In the face of the “momentary evil” of drunken driving, the Court today abdicates its role as the protector of that fundamental right. I respectfully dissent.

    Justice STEVENS, with whom Justice BRENNAN and Justice MARSHALL join as to Parts I and II, dissenting.

    A sobriety checkpoint is usually operated at night at an unannounced location. Surprise is crucial to its method. The test operation conducted by the Michigan State Police and the Saginaw County Sheriff’s Department began shortly after midnight and lasted until about 1 a.m. During that period, the 19 officers participating in the operation made two arrests and stopped and questioned 124 other unsuspecting and innocent drivers. It is, of course, not known how many arrests would have been made during that period if those officers had been engaged in normal patrol activities. However, the findings of the trial court, based on an extensive record and affirmed by the Michigan Court of Appeals, indicate that the net effect of sobriety checkpoints on traffic safety is infinitesimal and possibly negative.

    Indeed, the record in this case makes clear that a decision holding these suspicionless seizures unconstitutional would not impede the law enforcement community’s remarkable progress in reducing the death toll on our highways. Because the Michigan program was patterned after an older program in Maryland, the trial judge gave special attention to that State’s experience. Over a period of several years, Maryland operated 125 checkpoints; of the 41,000 motorists passing through those checkpoints, only 143 persons (0.3%) were arrested. The number of man-hours devoted to these operations is not in the record, but it seems inconceivable that a higher arrest rate could not have been achieved by more conventional means. Yet, even if the 143 checkpoint arrests were assumed to involve a net increase in the number of drunken driving arrests per year, the figure would still be insignificant by comparison to the 71,000 such arrests made by Michigan State Police without checkpoints in 1984 alone.

    Any relationship between sobriety checkpoints and an actual reduction in highway fatalities is even less substantial than the minimal impact on arrest rates. In light of these considerations, it seems evident that the Court today misapplies the balancing test. The Court overvalues the law enforcement interest in using sobriety checkpoints, undervalues the citizen’s interest in freedom from random, unannounced investigatory seizures, and mistakenly assumes that there is “virtually no difference” between a routine stop at a permanent, fixed checkpoint and a surprise stop at a sobriety checkpoint.

    This is a case that is driven by nothing more than symbolic state action—an insufficient justification for an otherwise unreasonable program of random seizures. Unfortunately, the Court is transfixed by the wrong symbol—the illusory prospect of punishing countless intoxicated motorists—when it should keep its eyes on the road plainly marked by the Constitution.

    I respectfully dissent.

    * * *

    In the next case, the Court considered whether the holding of Michigan v. Sitz allows police to conduct random (suspicionless) stops of vehicles to check whether they contain illegal drugs. While a checkpoint for “drugged” drivers would almost surely have been permissible for the same reasons that the Court permitted drunk driving checkpoints, the question of a checkpoint for contraband or other evidence of crime proved more controversial.

    Supreme Court of the United States

    City of Indianapolis v. James Edmond

    Decided Nov. 28, 2000 – 531 U.S. 32

    Justice O’CONNOR delivered the opinion of the Court.

    In Michigan Dept. of State Police v. Sitz and United States v. Martinez-Fuerte, we held that brief, suspicionless seizures at highway checkpoints for the purposes of combating drunk driving and intercepting illegal immigrants were constitutional. We now consider the constitutionality of a highway checkpoint program whose primary purpose is the discovery and interdiction of illegal narcotics.


    In August 1998, the city of Indianapolis began to operate vehicle checkpoints on Indianapolis roads in an effort to interdict unlawful drugs. The city conducted six such roadblocks between August and November that year, stopping 1,161 vehicles and arresting 104 motorists. Fifty-five arrests were for drug-related crimes, while 49 were for offenses unrelated to drugs. The overall “hit rate” of the program was thus approximately nine percent.

    The parties stipulated to the facts concerning the operation of the checkpoints by the Indianapolis Police Department (IPD) for purposes of the preliminary injunction proceedings instituted below. At each checkpoint location, the police stop a predetermined number of vehicles. Approximately 30 officers are stationed at the checkpoint. Pursuant to written directives issued by the chief of police, at least one officer approaches the vehicle, advises the driver that he or she is being stopped briefly at a drug checkpoint, and asks the driver to produce a license and registration. The officer also looks for signs of impairment and conducts an open-view examination of the vehicle from the outside. A narcotics-detection dog walks around the outside of each stopped vehicle.

    The directives instruct the officers that they may conduct a search only by consent or based on the appropriate quantum of particularized suspicion. The officers must conduct each stop in the same manner until particularized suspicion develops, and the officers have no discretion to stop any vehicle out of sequence. The city agreed in the stipulation to operate the checkpoints in such a way as to ensure that the total duration of each stop, absent reasonable suspicion or probable cause, would be five minutes or less.

    Respondents James Edmond and Joell Palmer were each stopped at a narcotics checkpoint in late September 1998. Respondents then filed a lawsuit on behalf of themselves and the class of all motorists who had been stopped or were subject to being stopped in the future at the Indianapolis drug checkpoints. Respondents claimed that the roadblocks violated the Fourth Amendment of the United States Constitution and the search and seizure provision of the Indiana Constitution. Respondents requested declaratory and injunctive relief for the class, as well as damages and attorney’s fees for themselves.

    Respondents then moved for a preliminary injunction. Although respondents alleged that the officers who stopped them did not follow the written directives, they agreed to the stipulation concerning the operation of the checkpoints for purposes of the preliminary injunction proceedings. The parties also stipulated to certification of the plaintiff class. The United States District Court for the Southern District of Indiana agreed to class certification and denied the motion for a preliminary injunction, holding that the checkpoint program did not violate the Fourth Amendment. A divided panel of the United States Court of Appeals for the Seventh Circuit reversed, holding that the checkpoints contravened the Fourth Amendment. The panel denied rehearing. We granted certiorari and now affirm.


    The Fourth Amendment requires that searches and seizures be reasonable. A search or seizure is ordinarily unreasonable in the absence of individualized suspicion of wrongdoing. While such suspicion is not an “irreducible” component of reasonableness, we have recognized only limited circumstances in which the usual rule does not apply. We have [] upheld brief, suspicionless seizures of motorists at a fixed Border Patrol checkpoint designed to intercept illegal aliens and at a sobriety checkpoint aimed at removing drunk drivers from the road. In addition we [have] suggested that a similar type of roadblock with the purpose of verifying drivers’ licenses and vehicle registrations would be permissible. In none of these cases, however, did we indicate approval of a checkpoint program whose primary purpose was to detect evidence of ordinary criminal wrongdoing.


    It is well established that a vehicle stop at a highway checkpoint effectuates a seizure within the meaning of the Fourth Amendment. The fact that officers walk a narcotics-detection dog around the exterior of each car at the Indianapolis checkpoints does not transform the seizure into a search. Just as in Place,1 an exterior sniff of an automobile does not require entry into the car and is not designed to disclose any information other than the presence or absence of narcotics. Like the dog sniff in Place, a sniff by a dog that simply walks around a car is “much less intrusive than a typical search.” Rather, what principally distinguishes these checkpoints from those we have previously approved is their primary purpose.

    As petitioners concede, the Indianapolis checkpoint program unquestionably has the primary purpose of interdicting illegal narcotics. In their stipulation of facts, the parties repeatedly refer to the checkpoints as “drug checkpoints” and describe them as “being operated by the City of Indianapolis in an effort to interdict unlawful drugs in Indianapolis.” In addition, the first document attached to the parties’ stipulation is entitled “DRUG CHECKPOINT CONTACT OFFICER DIRECTIVES BY ORDER OF THE CHIEF OF POLICE.” These directives instruct officers to “[a]dvise the citizen that they are being stopped briefly at a drug checkpoint.” The second document attached to the stipulation is entitled “1998 Drug Road Blocks” and contains a statistical breakdown of information relating to the checkpoints conducted. Further, according to Sergeant DePew, the checkpoints are identified with lighted signs reading, “‘NARCOTICS CHECKPOINT ___ MILE AHEAD, NARCOTICS K–9 IN USE, BE PREPARED TO STOP.’” Finally, both the District Court and the Court of Appeals recognized that the primary purpose of the roadblocks is the interdiction of narcotics.

    We have never approved a checkpoint program whose primary purpose was to detect evidence of ordinary criminal wrongdoing. Rather, our checkpoint cases have recognized only limited exceptions to the general rule that a seizure must be accompanied by some measure of individualized suspicion. [E]ach of the checkpoint programs that we have approved was designed primarily to serve purposes closely related to the problems of policing the border or the necessity of ensuring roadway safety. Because the primary purpose of the Indianapolis narcotics checkpoint program is to uncover evidence of ordinary criminal wrongdoing, the program contravenes the Fourth Amendment.

    Petitioners propose several ways in which the narcotics-detection purpose of the instant checkpoint program may instead resemble the primary purposes of the checkpoints in Sitz and Martinez-Fuerte. Petitioners state that the checkpoints in those cases had the same ultimate purpose of arresting those suspected of committing crimes. Securing the border and apprehending drunk drivers are, of course, law enforcement activities, and law enforcement officers employ arrests and criminal prosecutions in pursuit of these goals. If we were to rest the case at this high level of generality, there would be little check on the ability of the authorities to construct roadblocks for almost any conceivable law enforcement purpose. Without drawing the line at roadblocks designed primarily to serve the general interest in crime control, the Fourth Amendment would do little to prevent such intrusions from becoming a routine part of American life.

    Petitioners also emphasize the severe and intractable nature of the drug problem as justification for the checkpoint program. There is no doubt that traffic in illegal narcotics creates social harms of the first magnitude. The law enforcement problems that the drug trade creates likewise remain daunting and complex, particularly in light of the myriad forms of spin-off crime that it spawns. The same can be said of various other illegal activities, if only to a lesser degree. But the gravity of the threat alone cannot be dispositive of questions concerning what means law enforcement officers may employ to pursue a given purpose. Rather, in determining whether individualized suspicion is required, we must consider the nature of the interests threatened and their connection to the particular law enforcement practices at issue. We are particularly reluctant to recognize exceptions to the general rule of individualized suspicion where governmental authorities primarily pursue their general crime control ends.

    Nor can the narcotics-interdiction purpose of the checkpoints be rationalized in terms of a highway safety concern similar to that present in Sitz. The detection and punishment of almost any criminal offense serves broadly the safety of the community, and our streets would no doubt be safer but for the scourge of illegal drugs. Only with respect to a smaller class of offenses, however, is society confronted with the type of immediate, vehicle-bound threat to life and limb that the sobriety checkpoint in Sitz was designed to eliminate.

    The primary purpose of the Indianapolis narcotics checkpoints is in the end to advance “the general interest in crime control.” We decline to suspend the usual requirement of individualized suspicion where the police seek to employ a checkpoint primarily for the ordinary enterprise of investigating crimes. We cannot sanction stops justified only by the generalized and ever-present possibility that interrogation and inspection may reveal that any given motorist has committed some crime.

    Of course, there are circumstances that may justify a law enforcement checkpoint where the primary purpose would otherwise, but for some emergency, relate to ordinary crime control. For example, as the Court of Appeals noted, the Fourth Amendment would almost certainly permit an appropriately tailored roadblock set up to thwart an imminent terrorist attack or to catch a dangerous criminal who is likely to flee by way of a particular route. The exigencies created by these scenarios are far removed from the circumstances under which authorities might simply stop cars as a matter of course to see if there just happens to be a felon leaving the jurisdiction. While we do not limit the purposes that may justify a checkpoint program to any rigid set of categories, we decline to approve a program whose primary purpose is ultimately indistinguishable from the general interest in crime control.

    Petitioners argue that the Indianapolis checkpoint program is justified by its lawful secondary purposes of keeping impaired motorists off the road and verifying licenses and registrations. If this were the case, however, law enforcement authorities would be able to establish checkpoints for virtually any purpose so long as they also included a license or sobriety check. For this reason, we examine the available evidence to determine the primary purpose of the checkpoint program. While we recognize the challenges inherent in a purpose inquiry, courts routinely engage in this enterprise in many areas of constitutional jurisprudence as a means of sifting abusive governmental conduct from that which is lawful. As a result, a program driven by an impermissible purpose may be proscribed while a program impelled by licit purposes is permitted, even though the challenged conduct may be outwardly similar. While reasonableness under the Fourth Amendment is predominantly an objective inquiry, our special needs and administrative search cases demonstrate that purpose is often relevant when suspicionless intrusions pursuant to a general scheme are at issue.

    It goes without saying that our holding today does nothing to alter the constitutional status of the sobriety and border checkpoints that we approved in Sitz and Martinez-Fuerte. The constitutionality of such checkpoint programs still depends on a balancing of the competing interests at stake and the effectiveness of the program. When law enforcement authorities pursue primarily general crime control purposes at checkpoints such as here, however, stops can only be justified by some quantum of individualized suspicion.

    Our holding also does not affect the validity of border searches or searches at places like airports and government buildings, where the need for such measures to ensure public safety can be particularly acute. Nor does our opinion speak to other intrusions aimed primarily at purposes beyond the general interest in crime control. Our holding also does not impair the ability of police officers to act appropriately upon information that they properly learn during a checkpoint stop justified by a lawful primary purpose, even where such action may result in the arrest of a motorist for an offense unrelated to that purpose. Finally, we caution that the purpose inquiry in this context is to be conducted only at the programmatic level and is not an invitation to probe the minds of individual officers acting at the scene.

    Because the primary purpose of the Indianapolis checkpoint program is ultimately indistinguishable from the general interest in crime control, the checkpoints violate the Fourth Amendment. The judgment of the Court of Appeals is, accordingly, affirmed.

    Chief Justice REHNQUIST, with whom Justice THOMAS joins, and with whom Justice SCALIA joins as to Part I, dissenting.

    The State’s use of a drug-sniffing dog, according to the Court’s holding, annuls what is otherwise plainly constitutional under our Fourth Amendment jurisprudence: brief, standardized, discretionless, roadblock seizures of automobiles, seizures which effectively serve a weighty state interest with only minimal intrusion on the privacy of their occupants. Because these seizures serve the State’s accepted and significant interests of preventing drunken driving and checking for driver’s licenses and vehicle registrations, and because there is nothing in the record to indicate that the addition of the dog sniff lengthens these otherwise legitimate seizures, I dissent.

    As it is nowhere to be found in the Court’s opinion, I begin with blackletter roadblock seizure law. “The principal protection of Fourth Amendment rights at checkpoints lies in appropriate limitations on the scope of the stop.” Roadblock seizures are consistent with the Fourth Amendment if they are “carried out pursuant to a plan embodying explicit, neutral limitations on the conduct of individual officers.” Specifically, the constitutionality of a seizure turns upon “a weighing of the gravity of the public concerns served by the seizure, the degree to which the seizure advances the public interest, and the severity of the interference with individual liberty.”

    We first applied these principles in Martinez-Fuerte, which approved highway checkpoints for detecting illegal aliens. In Michigan Dept. of State Police v. Sitz, we upheld the State’s use of a highway sobriety checkpoint after applying the framework set out in Martinez-Fuerte. This case follows naturally from Martinez-Fuerte and Sitz. Petitioners acknowledge that the “primary purpose” of these roadblocks is to interdict illegal drugs, but this fact should not be controlling. Even accepting the Court’s conclusion that the checkpoints at issue in Martinez-Fuerte and Sitz were not primarily related to criminal law enforcement, the question whether a law enforcement purpose could support a roadblock seizure is not presented in this case. The District Court found that another “purpose of the checkpoints is to check driver’s licenses and vehicle registrations,” and the written directives state that the police officers are to “[l]ook for signs of impairment.” The use of roadblocks to look for signs of impairment was validated by Sitz, and the use of roadblocks to check for driver’s licenses and vehicle registrations was expressly recognized in Delaware v. Prouse, 440 U.S.648 (1979). That the roadblocks serve these legitimate state interests cannot be seriously disputed, as the 49 people arrested for offenses unrelated to drugs can attest. And it would be speculative to conclude—given the District Court’s findings, the written directives, and the actual arrests—that petitioners would not have operated these roadblocks but for the State’s interest in interdicting drugs.

    Because of the valid reasons for conducting these roadblock seizures, it is constitutionally irrelevant that petitioners also hoped to interdict drugs. Once the constitutional requirements for a particular seizure are satisfied, the subjective expectations of those responsible for it, be it police officers or members of a city council, are irrelevant. It is the objective effect of the State’s actions on the privacy of the individual that animates the Fourth Amendment. Because the objective intrusion of a valid seizure does not turn upon anyone’s subjective thoughts, neither should our constitutional analysis.

    With these checkpoints serving two important state interests, the remaining prongs of the balancing test are easily met. The seizure is objectively reasonable as it lasts, on average, two to three minutes and does not involve a search. The subjective intrusion is likewise limited as the checkpoints are clearly marked and operated by uniformed officers who are directed to stop every vehicle in the same manner. The only difference between this case and Sitz is the presence of the dog. We have already held, however, that a “sniff test” by a trained narcotics dog is not a “search” within the meaning of the Fourth Amendment because it does not require physical intrusion of the object being sniffed and it does not expose anything other than the contraband items. And there is nothing in the record to indicate that the dog sniff lengthens the stop. Finally, the checkpoints’ success rate—49 arrests for offenses unrelated to drugs—only confirms the State’s legitimate interests in preventing drunken driving and ensuring the proper licensing of drivers and registration of their vehicles.

    These stops effectively serve the State’s legitimate interests; they are executed in a regularized and neutral manner; and they only minimally intrude upon the privacy of the motorists. They should therefore be constitutional.

    * * *

    In the next case, the Court considered a police checkpoint designed to find witnesses of a recent crime—a hit-and-run crash. Like Indianapolis v. Edmond, and unlike Michigan v. Sitz, the case involved stopping vehicles without any purpose of protecting the public from immediate hazards presented by their drivers. However, unlike Edmond, police did not hope to find evidence of wrongdoing by the drivers; instead, they hoped to learn whether the drivers had seen wrongdoing by someone else.

    Supreme Court of the United States

    Illinois v. Robert S. Lidster

    Decided Jan. 13, 2004 – 540 U.S. 419

    Justice BREYER delivered the opinion of the Court.

    This Fourth Amendment case focuses upon a highway checkpoint where police stopped motorists to ask them for information about a recent hit-and-run accident. We hold that the police stops were reasonable, hence, constitutional.


    The relevant background is as follows: On Saturday, August 23, 1997, just after midnight, an unknown motorist traveling eastbound on a highway in Lombard, Illinois, struck and killed a 70–year–old bicyclist. The motorist drove off without identifying himself. About one week later at about the same time of night and at about the same place, local police set up a highway checkpoint designed to obtain more information about the accident from the motoring public.

    Police cars with flashing lights partially blocked the eastbound lanes of the highway. The blockage forced traffic to slow down, leading to lines of up to 15 cars in each lane. As each vehicle drew up to the checkpoint, an officer would stop it for 10 to 15 seconds, ask the occupants whether they had seen anything happen there the previous weekend, and hand each driver a flyer. The flyer said “ALERT … FATAL HIT & RUN ACCIDENT” and requested “ASSISTANCE IN IDENTIFYING THE VEHICLE AND DRIVER INVOLVED IN THIS ACCIDENT WHICH KILLED A 70 YEAR OLD BICYCLIST.”

    Robert Lidster, the respondent, drove a minivan toward the checkpoint. As he approached the checkpoint, his van swerved, nearly hitting one of the officers. The officer smelled alcohol on Lidster’s breath. He directed Lidster to a side street where another officer administered a sobriety test and then arrested Lidster. Lidster was tried and convicted in Illinois state court of driving under the influence of alcohol.

    Lidster challenged the lawfulness of his arrest and conviction on the ground that the government had obtained much of the relevant evidence through use of a checkpoint stop that violated the Fourth Amendment. The trial court rejected that challenge. But an Illinois appellate court reached the opposite conclusion. The Illinois Supreme Court agreed with the appellate court.

    [W]e granted certiorari. We now reverse the Illinois Supreme Court’s determination.


    The Illinois Supreme Court basically held that our decision in Edmond governs the outcome of this case. We do not agree. Edmond involved a checkpoint at which police stopped vehicles to look for evidence of drug crimes committed by occupants of those vehicles.

    The checkpoint stop here differs significantly from that in Edmond. The stop’s primary law enforcement purpose was not to determine whether a vehicle’s occupants were committing a crime, but to ask vehicle occupants, as members of the public, for their help in providing information about a crime in all likelihood committed by others. The police expected the information elicited to help them apprehend, not the vehicle’s occupants, but other individuals.

    Edmond’s language, as well as its context, makes clear that the constitutionality of this latter, information-seeking kind of stop was not then before the Court. Neither do we believe, Edmond aside, that the Fourth Amendment would have us apply an Edmond-type rule of automatic unconstitutionality to brief, information-seeking highway stops of the kind now before us. For one thing, the fact that such stops normally lack individualized suspicion cannot by itself determine the constitutional outcome. As in Edmond, the stop here at issue involves a motorist. The Fourth Amendment does not treat a motorist’s car as his castle. And special law enforcement concerns will sometimes justify highway stops without individualized suspicion. Moreover, unlike Edmond, the context here (seeking information from the public) is one in which, by definition, the concept of individualized suspicion has little role to play. Like certain other forms of police activity, say, crowd control or public safety, an information-seeking stop is not the kind of event that involves suspicion, or lack of suspicion, of the relevant individual.

    For another thing, information-seeking highway stops are less likely to provoke anxiety or to prove intrusive. The stops are likely brief. The police are not likely to ask questions designed to elicit self-incriminating information. And citizens will often react positively when police simply ask for their help as “responsible citizen[s]” to “give whatever information they may have to aid in law enforcement.

    Further, the law ordinarily permits police to seek the voluntary cooperation of members of the public in the investigation of a crime. “[L]aw enforcement officers do not violate the Fourth Amendment by merely approaching an individual on the street or in another public place, by asking him if he is willing to answer some questions, [or] by putting questions to him if the person is willing to listen.” That, in part, is because voluntary requests play a vital role in police investigatory work.

    The importance of soliciting the public’s assistance is offset to some degree by the need to stop a motorist to obtain that help—a need less likely present where a pedestrian, not a motorist, is involved. The difference is significant in light of our determinations that such an involuntary stop amounts to a “seizure” in Fourth Amendment terms. That difference, however, is not important enough to justify an Edmond-type rule here. After all, as we have said, the motorist stop will likely be brief. Any accompanying traffic delay should prove no more onerous than many that typically accompany normal traffic congestion. And the resulting voluntary questioning of a motorist is as likely to prove important for police investigation as is the questioning of a pedestrian. Given these considerations, it would seem anomalous were the law (1) ordinarily to allow police freely to seek the voluntary cooperation of pedestrians but (2) ordinarily to forbid police to seek similar voluntary cooperation from motorists.

    Finally, we do not believe that an Edmond-type rule is needed to prevent an unreasonable proliferation of police checkpoints. Practical considerations—namely, limited police resources and community hostility to related traffic tieups—seem likely to inhibit any such proliferation. And, of course, the Fourth Amendment’s normal insistence that the stop be reasonable in context will still provide an important legal limitation on police use of this kind of information-seeking checkpoint.

    These considerations, taken together, convince us that an Edmond-type presumptive rule of unconstitutionality does not apply here. That does not mean the stop is automatically, or even presumptively, constitutional. It simply means that we must judge its reasonableness, hence, its constitutionality, on the basis of the individual circumstances. And as this Court said in Brown v. Texas, 443 U.S.47 (1979), in judging reasonableness, we look to “the gravity of the public concerns served by the seizure, the degree to which the seizure advances the public interest, and the severity of the interference with individual liberty.”


    We now consider the reasonableness of the checkpoint stop before us in light of the factors just mentioned, an issue that, in our view, has been fully argued here. We hold that the stop was constitutional.

    The relevant public concern was grave. Police were investigating a crime that had resulted in a human death. No one denies the police’s need to obtain more information at that time. And the stop’s objective was to help find the perpetrator of a specific and known crime, not of unknown crimes of a general sort.

    The stop advanced this grave public concern to a significant degree. The police appropriately tailored their checkpoint stops to fit important criminal investigatory needs. The stops took place about one week after the hit-and-run accident, on the same highway near the location of the accident, and at about the same time of night. And police used the stops to obtain information from drivers, some of whom might well have been in the vicinity of the crime at the time it occurred.

    Most importantly, the stops interfered only minimally with liberty of the sort the Fourth Amendment seeks to protect. Viewed objectively, each stop required only a brief wait in line—a very few minutes at most. Contact with the police lasted only a few seconds. Police contact consisted simply of a request for information and the distribution of a flyer. Viewed subjectively, the contact provided little reason for anxiety or alarm. The police stopped all vehicles systematically. And there is no allegation here that the police acted in a discriminatory or otherwise unlawful manner while questioning motorists during stops.

    For these reasons we conclude that the checkpoint stop was constitutional.

    The judgment of the Illinois Supreme Court is [r]eversed.

    Notes, Comments, and Questions

    The Court made clear in Indianapolis v. Edmond that police may not establish checkpoints to investigate whether drivers are transporting illegal drugs. Consider a department that responds as follows:

    Police post signs with text like “Drug Checkpoint Ahead” on public highways. Then, after observing drivers who promptly exit the highway after passing the sign, officers investigate the drivers for drug activity. Lawful? Why or why not?

    See, e.g., United States v. Williams, 359 F.3d 1019 (8th Cir. 2004) (holding that because “there was no checkpoint,” Edmond did not apply); United States v. Neff, 681 F.3d 1134 (10th Cir. 2012) (holding that the fake-checkpoint ruse was lawful but that “standing alone,” a driver’s choice to exit after seeing the sign “is insufficient to justify even a brief investigatory detention of a vehicle”); compare State v. Mack, 66 S.W.3d 706 (Mo. 2002) (finding that “it is reasonable to conclude that drivers with drugs would ‘take the bait’ and exit” and holding that stop was reasonable in part because “the checkpoint was set up in an isolated and sparsely populated area offering no services to motorists and was conducted on an evening that would otherwise have little traffic”); with id. at 710 (Stith, J., dissenting) (arguing that seizure was unreasonable under Edmond).

    If a driver exiting the highway immediately after passing a “drug checkpoint ahead” sign is not sufficient to provide reasonable suspicion to justify a vehicle stop (as the Tenth Circuit held), what else should be necessary to justify the stop? In other words, what else must an officer observe after the car exits?

    This tactic has attracted attention from the surveilled community. See, e.g., Steve Elliot, “Cops Set Up Fake ‘Drug Checkpoint’ Signs; Detain and Search Drivers Who React,” Toke Signals (Jan. 28, 2014); TJ Green, “Fake Drug Checkpoints Are Becoming More Devious,” Weed Blog (May 3, 2012).

    Warrant Exception: Protective Sweeps

    Our final case for this chapter concerns “protective sweeps,” which police may conduct along with an arrest to protect themselves and others from potential attackers who may be lying in wait. Students should carefully note how the protective sweeps doctrine differs from that regulating searches incident to lawful arrests.

    Supreme Court of the United States

    Maryland v. Jerome Edward Buie

    Decided Feb. 28, 1990 – 494 U.S. 325

    Justice WHITE delivered the opinion of the Court.

    A “protective sweep” is a quick and limited search of premises, incident to an arrest and conducted to protect the safety of police officers or others. It is narrowly confined to a cursory visual inspection of those places in which a person might be hiding. In this case we must decide what level of justification is required by the Fourth and Fourteenth Amendments before police officers, while effecting the arrest of a suspect in his home pursuant to an arrest warrant, may conduct a warrantless protective sweep of all or part of the premises. The Court of Appeals of Maryland held that a running suit seized in plain view during such a protective sweep should have been suppressed at respondent’s armed robbery trial because the officer who conducted the sweep did not have probable cause to believe that a serious and demonstrable potentiality for danger existed. We conclude that the Fourth Amendment would permit the protective sweep undertaken here if the searching officer “possesse[d] a reasonable belief based on ‘specific and articulable facts which, taken together with the rational inferences from those facts, reasonably warrant[ed]’ the officer in believing” that the area swept harbored an individual posing a danger to the officer or others. We accordingly vacate the judgment below and remand for application of this standard.


    On February 3, 1986, two men committed an armed robbery of a Godfather’s Pizza restaurant in Prince George’s County, Maryland. One of the robbers was wearing a red running suit. That same day, Prince George’s County police obtained arrest warrants for respondent Jerome Edward Buie and his suspected accomplice in the robbery, Lloyd Allen. Buie’s house was placed under police surveillance.

    On February 5, the police executed the arrest warrant for Buie. They first had a police department secretary telephone Buie’s house to verify that he was home. The secretary spoke to a female first, then to Buie himself. Six or seven officers proceeded to Buie’s house. Once inside, the officers fanned out through the first and second floors. Corporal James Rozar announced that he would “freeze” the basement so that no one could come up and surprise the officers. With his service revolver drawn, Rozar twice shouted into the basement, ordering anyone down there to come out. When a voice asked who was calling, Rozar announced three times: “this is the police, show me your hands.” Eventually, a pair of hands appeared around the bottom of the stairwell and Buie emerged from the basement. He was arrested, searched, and handcuffed by Rozar. Thereafter, Detective Joseph Frolich entered the basement “in case there was someone else” down there. He noticed a red running suit lying in plain view on a stack of clothing and seized it.

    The trial court denied Buie’s motion to suppress the running suit, stating in part: “The man comes out from a basement, the police don’t know how many other people are down there. He is charged with a serious offense.” The State introduced the running suit into evidence at Buie’s trial. A jury convicted Buie of robbery with a deadly weapon and using a handgun in the commission of a felony.

    The Court of Special Appeals of Maryland affirmed the trial court’s denial of the suppression motion. The court stated that Detective Frolich did not go into the basement to search for evidence, but to look for the suspected accomplice or anyone else who might pose a threat to the officers on the scene.

    The Court of Appeals of Maryland reversed by a 4-to-3 vote. The court acknowledged that “when the intrusion is slight, as in the case of a brief stop and frisk on a public street, and the public interest in prevention of crime is substantial, reasonable articulable suspicion may be enough to pass constitutional muster.” The court, however, stated that when the sanctity of the home is involved, the exceptions to the warrant requirement are few, and held: “[T]o justify a protective sweep of a home, the government must show that there is probable cause to believe that ‘“a serious and demonstrable potentiality for danger”’ exists.” The court went on to find that the State had not satisfied that probable-cause requirement.


    It is not disputed that until the point of Buie’s arrest the police had the right, based on the authority of the arrest warrant, to search anywhere in the house that Buie might have been found, including the basement. “If there is sufficient evidence of a citizen’s participation in a felony to persuade a judicial officer that his arrest is justified, it is constitutionally reasonable to require him to open his doors to the officers of the law.” There is also no dispute that if Detective Frolich’s entry into the basement was lawful, the seizure of the red running suit, which was in plain view and which the officer had probable cause to believe was evidence of a crime, was also lawful under the Fourth Amendment. The issue in this case is what level of justification the Fourth Amendment required before Detective Frolich could legally enter the basement to see if someone else was there.

    Petitioner, the State of Maryland, argues that, under a general reasonableness balancing test, police should be permitted to conduct a protective sweep whenever they make an in-home arrest for a violent crime.


    It goes without saying that the Fourth Amendment bars only unreasonable searches and seizures. Our cases show that in determining reasonableness, we have balanced the intrusion on the individual’s Fourth Amendment interests against its promotion of legitimate governmental interests. Under this test, a search of the house or office is generally not reasonable without a warrant issued on probable cause. There are other contexts, however, where the public interest is such that neither a warrant nor probable cause is required.

    Possessing an arrest warrant and probable cause to believe Buie was in his home, the officers were entitled to enter and to search anywhere in the house in which Buie might be found. Once he was found, however, the search for him was over, and there was no longer that particular justification for entering any rooms that had not yet been searched.

    That Buie had an expectation of privacy in those remaining areas of his house, however, does not mean such rooms were immune from entry. In the instant case, there is an [] interest of the officers in taking steps to assure themselves that the house in which a suspect is being, or has just been, arrested is not harboring other persons who are dangerous and who could unexpectedly launch an attack. The risk of danger in the context of an arrest in the home is as great as, if not greater than, it is in an on-the-street or roadside investigatory encounter. A protective sweep, in contrast, occurs as an adjunct to the serious step of taking a person into custody for the purpose of prosecuting him for a crime. Moreover, unlike an encounter on the street or along a highway, an in-home arrest puts the officer at the disadvantage of being on his adversary’s “turf.” An ambush in a confined setting of unknown configuration is more to be feared than it is in open, more familiar surroundings.

    We agree with the State, as did the court below, that a warrant was not required. We also hold that as an incident to the arrest the officers could, as a precautionary matter and without probable cause or reasonable suspicion, look in closets and other spaces immediately adjoining the place of arrest from which an attack could be immediately launched. Beyond that, however, we hold that there must be articulable facts which, taken together with the rational inferences from those facts, would warrant a reasonably prudent officer in believing that the area to be swept harbors an individual posing a danger to those on the arrest scene. This is no more and no less than was required in Terry and Long, and as in those cases, we think this balance is the proper one.2

    We should emphasize that such a protective sweep, aimed at protecting the arresting officers, if justified by the circumstances, is nevertheless not a full search of the premises, but may extend only to a cursory inspection of those spaces where a person may be found. The sweep lasts no longer than is necessary to dispel the reasonable suspicion of danger and in any event no longer than it takes to complete the arrest and depart the premises.


    The type of search we authorize today is far removed from the “top-to-bottom” search involved in Chimel; moreover, it is decidedly not “automati[c],” but may be conducted only when justified by a reasonable, articulable suspicion that the house is harboring a person posing a danger to those on the arrest scene.


    We conclude that by requiring a protective sweep to be justified by probable cause to believe that a serious and demonstrable potentiality for danger existed, the Court of Appeals of Maryland applied an unnecessarily strict Fourth Amendment standard. The Fourth Amendment permits a properly limited protective sweep in conjunction with an in-home arrest when the searching officer possesses a reasonable belief based on specific and articulable facts that the area to be swept harbors an individual posing a danger to those on the arrest scene. We therefore vacate the judgment below and remand this case to the Court of Appeals of Maryland for further proceedings not inconsistent with this opinion.

    Justice STEVENS, concurring.

    Today the Court holds that reasonable suspicion, rather than probable cause, is necessary to support a protective sweep while an arrest is in progress. I agree with that holding and with the Court’s opinion, but I believe it is important to emphasize that the standard applies only to protective sweeps. Officers conducting such a sweep must have a reasonable basis for believing that their search will reduce the danger of harm to themselves or of violent interference with their mission; in short, the search must be protective.

    In this case, to justify Officer Frolich’s entry into the basement, it is the State’s burden to demonstrate that the officers had a reasonable basis for believing not only that someone in the basement might attack them or otherwise try to interfere with the arrest, but also that it would be safer to go down the stairs instead of simply guarding them from above until respondent had been removed from the house. The fact that respondent offered no resistance when he emerged from the basement is somewhat inconsistent with the hypothesis that the danger of an attack by a hidden confederate persisted after the arrest. Moreover, Officer Rozar testified that he was not worried about any possible danger when he arrested Buie.

    Indeed, were the officers concerned about safety, one would expect them to do what Officer Rozar did before the arrest: guard the basement door to prevent surprise attacks. As the Court indicates, Officer Frolich might, at the time of the arrest, reasonably have “look[ed] in” the already open basement door to ensure that no accomplice had followed Buie to the stairwell. But Officer Frolich did not merely “look in” the basement; he entered it. That strategy is sensible if one wishes to search the basement. It is a surprising choice for an officer, worried about safety, who need not risk entering the stairwell at all.

    The State may thus face a formidable task on remand. However, the Maryland courts are better equipped than are we to review the record.

    Justice KENNEDY, concurring.

    The Court adopts the prudent course of explaining the general rule and permitting the state court to apply it in the first instance. The concurrence by JUSTICE STEVENS, however, makes the gratuitous observation that the State has a formidable task on remand. My view is quite to the contrary. Based on my present understanding of the record, I should think the officers’ conduct here was in full accord with standard police safety procedure, and that the officers would have been remiss if they had not taken these precautions. This comment is necessary, lest by acquiescence the impression be left that JUSTICE STEVENS’ views can be interpreted as authoritative guidance for application of our ruling to the facts of the case.

    Justice BRENNAN, with whom Justice MARSHALL joins, dissenting.

    While the Fourth Amendment protects a person’s privacy interests in a variety of settings, “physical entry of the home is the chief evil against which the wording of the Fourth Amendment is directed.” The Court discounts the nature of the intrusion because it believes that the scope of the intrusion is limited. The Court explains that a protective sweep’s scope is “narrowly confined to a cursory visual inspection of those places in which a person might be hiding” and confined in duration to a period “no longer than is necessary to dispel the reasonable suspicion of danger and in any event no longer than it takes to complete the arrest and depart the premises.” But these spatial and temporal restrictions are not particularly limiting. A protective sweep would bring within police purview virtually all personal possessions within the house not hidden from view in a small enclosed space. Police officers searching for potential ambushers might enter every room including basements and attics; open up closets, lockers, chests, wardrobes, and cars; and peer under beds and behind furniture. The officers will view letters, documents, and personal effects that are on tables or desks or are visible inside open drawers; books, records, tapes, and pictures on shelves; and clothing, medicines, toiletries and other paraphernalia not carefully stored in dresser drawers or bathroom cupboards. While perhaps not a “full-blown” or “top-to-bottom” search, a protective sweep is much closer to it than to a “limited patdown for weapons” or a “‘frisk’ of an automobile.”

    In light of the special sanctity of a private residence and the highly intrusive nature of a protective sweep, I firmly believe that police officers must have probable cause to fear that their personal safety is threatened by a hidden confederate of an arrestee before they may sweep through the entire home. Given the state-court determination that the officers searching Buie’s home lacked probable cause to perceive such a danger and therefore were not lawfully present in the basement, I would affirm the state court’s decision to suppress the incriminating evidence. I respectfully dissent.

    Notes, Comments, and Questions

    When comparing lawful “protective sweeps” with searches incident to lawful arrest, students should note (1) the physical scope of a protective sweep will often extend beyond the area in which a SILA is permissible, (2) because sweeps are permitted only to protect against dangers to those present during the arrest, police may search only areas in which an officer may reasonably suspect a person could be found, and (3) the searches must be “cursory inspections” of those spaces.

    An open question related to prospective sweeps concerns whether police may conduct them upon entering a house with consent—or in other contexts unrelated to arrests.3 Federal courts have reached divergent results.

    Imagine police are investigating a brutal murder of a gang member and suspect that a rival gang is responsible. They obtain consent to enter the home of a witness in a “high-crime” neighborhood. May they “sweep” the house upon entry? Why or why not?

    Consider a slightly modified version of the problem presented above. Here, police are investigating an allegation of insider trading that violates federal securities law. They obtain consent to enter the home of a witness in an exclusive gated community. May they “sweep” the house upon entry? Why or why not?

    For courts permitting sweeps absent arrests, see, e.g., United States v. Fadual, 16 F. Supp. 3d 270 (S.D.N.Y. 2014) (holding that “under certain circumstances, law enforcement officers may engage in a protective sweep where they gained entry through consent in the first instance” but that the sweep at issue was not lawful); United States v. Miller, 430 F.3d 93, 95 (2d Cir. 2005) (allowing sweeps made by the police pursuant to “lawful process, such as an order permitting or directing the officer to enter for the purpose of protecting a third party”); United States v. Gould, 364 F.3d 578 (5th Cir. 2004) (allowing sweep of mobile home entered by police with consent). For courts holding sweeps unlawful absent an arrest, see, e.g., United States v. Torres-Castro, 470 F.3d 992 (10th Cir. 2006) (“Following Buie, we held that such ‘protective sweeps’ are only permitted incident to an arrest.”); United States v. Waldner, 425 F.3d 514, 517 (8th Cir. 2005) (declining the invitation to “extend Buie further”); United States v. Reid, 226 F.3d 1020, 1027 (9th Cir. 2000) (holding search cannot be justified as protective sweep because when it occurred suspect “was not under arrest”).