Mr. Justice Powell
delivered the opinion of the Court.
These cases involve criminal prosecutions for offenses relating to the transportation of illegal Mexican aliens. Each defendant was arrested at a permanent checkpoint operated by the Border Patrol' away from the international border with Mexico, and each sought the exclusion of certain evidence on the ground that the operation of the checkpoint was incompatible with the Fourth Amendment. In each instance whether the Fourth Amendment was violated turns primarily on whether a vehicle may be stopped at a fixed checkpoint for brief questioning of its occupants even though there is no reason, to believe the particular vehicle contains illegal aliens. We reserved this question last Term in United States v. Ortiz, 422 U. S. 891, 897 n. 3 (1975). We hold today that such stops are consistent with the Fourth Amendment. We also hold that the operation of a fixed checkpoint need not be authorized in advance by a judicial warrant.
I
A
The respondents in No. 74 — 1560 are defendants in three separate prosecutions resulting from arrests made on three different occasions at the permanent immigration checkpoint on Interstate 5 near San Clemente, Cal. Interstate 5 is the principal highway between San Diego and Los Angeles, and the San Clemente checkpoint is 66 road miles north of the Mexican border. We previously have described the checkpoint as follows:
“ 'Approximately one mile south of the checkpoint is a large black on yellow sign with flashing yellow lights over the highway stating “ALL VEHICLES, STOP AHEAD, 1 MILE.” Three-quarters of a mile further north are two black on yellow signs suspended over the highway with flashing lights stating “WATCH FOR BRAKE LIGHTS.” At the checkpoint, which is also the location of a State of California weighing station, are two large signs with flashing red lights suspended over the highway. These signs each state “STOP HERE — U. S. OFFICERS.” Placed on the highway are a number of orange traffic cones funneling traffic into two lanes where a Border Patrol agent in full dress uniform, standing behind a white on red “STOP” sign checks traffic. Blocking traffic in the unused lanes are official U. S. Border Patrol vehicles with flashing red lights. In addition, there is a permanent building which houses the Border Patrol office and temporary detention facilities. There are also floodlights for nighttime operation.’ ” United States v. Ortiz, supra, at 893, quoting United States v. Baca, 368 F. Supp. 398, 410-411 (SD Cal. 1973).
The “point” agent standing between the two lanes of traffic visually screens all northbound vehicles, which the checkpoint brings to a virtual, if not a complete, halt. Most motorists are allowed to resume their progress without any oral inquiry or close visual examination. In a relatively small number of cases the “point” agent will conclude that further inquiry is in order. He directs these cars to a secondary inspection area, where their occupants are asked about their citizenship and immigration status. The Government informs us that at San Clemente the average length of an investigation in the secondary inspection area is three to five minutes. Brief for United States 53. A direction to stop in the secondary inspection area could be based on something suspicious about a particular car passing through the checkpoint, but the Government concedes that none of the three stops at issue in No. 74-1560 was based on any articulable suspicion. During the period when these stops were made, the checkpoint was operating under a magistrate’s “warrant of inspection,” which authorized the Border Patrol to conduct a routine-stop operation at the San Clemente location.
We turn now to the particulars of the stops involved in No. 74-1560, and the procedural history of the case. Respondent Amado Martinez-Fuerte approached the checkpoint driving a vehicle containing two female passengers. The women were illegal Mexican aliens who had entered the United States at the San Ysidro port of entry by using false papers and rendezvoused with Martinez-Fuerte in San Diego to be transported northward. At the checkpoint their car was directed to the secondary inspection area. Martinez-Fuerte produced documents showing him to be a lawful resident alien, but his passengers admitted being present in the country unlawfully. He was charged, inter alia, with two counts of illegally transporting aliens in violation of 8 U. S. C. § 1324 (a)(2). He moved before trial to suppress all evidence stemming from the stop on the ground that the operation of the checkpoint was in violation of the Fourth Amendment. The motion to suppress was denied, and he was convicted on both counts after a jury trial.
Respondent Jose Jiminez-Garcia attempted to pass through the checkpoint while driving a car containing one passenger. He had picked the passenger up- by prearrangement in San Ysidro after the latter had been smuggled across the border. Questioning at the secondary inspection area revealed the illegal status of the passenger, and Jiminez-Garcia was charged in two counts with illegally transporting an alien, 8 U. S. C. § 1324 (a) (2), and conspiring to commit that offense, 18 U. S. C. § 371. His motion to suppress the evidence derived from the stop- was granted.
Respondents Raymond Guillen and Fernando Me-drano-Barragan approached the checkpoint with Guillen driving and Medrano-Barragan and his wife as passengers. Questioning at the secondary inspection area revealed that Medrano-Barragan and his wife were illegal aliens. A subsequent search of the car uncovered three other illegal aliens in the trunk. Medrano-Barragan had led the other aliens across the border at the beach near Tijuana, Mexico, where they rendezvoused with Guillen, a United States citizen. Guillen and Medrano-Barragan were jointly indicted on four counts of illegally transporting aliens, 8 U. S. C. § 1324 (a)(2), four counts of inducing the illegal entry of aliens, § 1324 (a)(4), and one conspiracy count, 18 U. S. C. § 371. The District Court granted the defendants' motion to suppress.
Martinez-Fuerte appealed his conviction, and the Government appealed the granting of the motions to suppress in the respective prosecutions of Jiminez-Garcia and of Guillen and Medrano-Barragan. The Court of Appeals for the Ninth Circuit consolidated the three appeals, which presented the common question whether routine stops and interrogations at checkpoints are consistent with the Fourth Amendment. The Court of Appeals held, with one judge dissenting, that these stops violated the Fourth Amendment, concluding that a stop for inquiry is constitutional only if the Border Patrol reasonably suspects the presence of illegal aliens on the basis of articulable facts. It reversed Martinez-Fuerte’s conviction, and affirmed the orders to suppress in the other cases. 514 F. 2d 308 (1975). We reverse and remand.
B
Petitioner in No. 75-5387, Rodolfo Sifuentes, was arrested at the permanent immigration checkpoint on U. S. Highway 77 near Sarita, Tex. Highway 77 originates in Brownsville, and it is one of the two major highways running north from the lower Rio Grande valley. The Sarita checkpoint is about 90 miles north of Brownsville, and 65-90 miles from the nearest points of the Mexican border. The physical arrangement of the checkpoint resembles generally that at San Clemente, but the checkpoint is operated differently in that the officers customarily stop all northbound motorists for a brief inquiry. Motorists whom the officers recognize as local inhabitants, however, are waved through the checkpoint without inquiry. Unlike the San Clemente checkpoint the Sarita operation was conducted without a judicial warrant.
Sifuentes drove up to the checkpoint without any visible passengers. When an agent approached the vehicle, however, he observed four passengers, one in the front seat and the other three in the rear, slumped down in the seats. Questioning revealed that each passenger was an illegal alien, although Sifuentes was a United States citizen. The aliens had met Sifuentes in the United States, by prearrangement, after swimming across the Rio Grande.
Sifuentes was indicted on four counts of illegally transporting aliens. 8 U. S. C. § 1324 (a)(2). He moved on Fourth Amendment grounds to suppress the evidence derived from the stop. The motion was denied and he was convicted after a jury trial. Sifuentes renewed his Fourth Amendment argument on appeal, contending primarily that stops made without reason to believe a car is transporting aliens illegally are unconstitutional. The United States Court of Appeals for the Fifth Circuit affirmed the conviction, 517 F. 2d 1402 (1975), relying on its opinion in United States v. Santibanez, 517 F. 2d 922 (1975). There the Court of Appeals had ruled that routine checkpoint stops are consistent with the Fourth- Amendment. We affirm.
II
The Courts of Appeals for the Ninth and the Fifth Circuits are in conflict on the constitutionality of a law enforcement technique considered, important by those charged with policing the Nation’s borders. Before turning to the constitutional question, we examine the context in which it arises.
A
It has been national policy for many years to limit immigration into the United States. Since July 1, 1968, the annual quota for immigrants from all independent countries of the Western Hemisphere, including Mexico, has been 120,000 persons. Act of Oct. 3, 1965, § 21 (e), 79 Stat. 921. Many more aliens than can be accommodated under the quota want to live and work in the United States. Consequently, large numbers of aliens seek illegally to enter or to remain in the United States. We noted last Term that “ [estimates of the number of illegal immigrants [already] in the United States vary widely. A conservative estimate in 1972 produced a figure of about one million, but the Immigration and Naturalization Service now suggests there may be as many as 10 or 12 million aliens illegally in the country.” United States v. Brignoni-Ponce, 422 U. S. 873, 878 (1975) (footnote omitted). It is estimated that 85% of the illegal immigrants are from Mexico, drawn by the fact that economic opportunities are significantly greater in the United States than they are in Mexico. United States v. Baca, 368 F. Supp., at 402.
Interdicting the flow of illegal entrants from Mexico poses formidable law enforcement problems. The principal problem arises from surreptitious entries. Id,., at 405. The United States shares a border with Mexico that is almost 2,000 miles long, and much of the border area is uninhabited desert or thinly populated arid land. Although the Border Patrol maintains personnel, electronic equipment, and fences along portions of the border, it remains relatively easy for individuals to enter the United States without detection. It also is possible for an alien to enter unlawfully at a port of entry by the use of falsified papers or to enter lawfully but violate restrictions of entry in an effort to remain in the country unlawfully. Once within the country, the aliens seek to travel inland to areas where employment is believed to be available, frequently meeting by prearrangement with friends or professional smugglers who transport them in private vehicles. United States v. Brignoni-Ponce, supra, at 879.
The Border Patrol conducts three kinds of inland traffic-checking operations in an effort to minimize illegal immigration. Permanent checkpoints, such as those at San Clemente and Sarita, are maintained at or near intersections of important roads leading away from the border. They operate on a coordinated basis designed to avoid circumvention by smugglers and others who transport the illegal aliens. Temporary checkpoints, which operate like permanent ones, occasionally are established in other strategic locations. Finally, roving patrols are maintained to supplement the checkpoint system. See Almeida-Sanchez v. United States, 413 U. S. 266, 268 (1973). In fiscal 1973, 175,-511 deportable aliens were apprehended throughout the Nation by “line watch” agents stationed at the border itself. Traffic-checking operations in the interior apprehended approximately 55,300 more deportable aliens. Most of the traffic-checking apprehensions were at checkpoints, though precise figures are not available. United States v. Baca, supra, at 405, 407, and n. 2.
B
We are concerned here with permanent checkpoints, the locations of which are chosen on the basis of a number of factors. The Border Patrol believes that to assure effectiveness, a checkpoint must be (i) distant enough from the border to avoid interference with traffic in populated areas near the border, (ii) close to the confluence of two or more significant roads leading away from the border, (iii) situated in terrain that restricts vehicle passage around the checkpoint, (iv) on a stretch of highway compatible with safe operation, and (v) beyond the 25-mile zone in which “border passes,” see n. 7, supra, are valid. United States v. Baca, supra, at 406.
The record in No. 74-1560 provides a rather complete picture of the effectiveness of the San Clemente checkpoint. Approximately 10 million cars pass the checkpoint location each year, although the checkpoint actually is in operation only about 70% of the time. In calendar year 1973, approximately 17,000 illegal aliens were apprehended there. During an eight-day period in 1974 that included the arrests involved in No. 74^1560, roughly 146,000 vehicles passed through the checkpoint during 124% hours of operation. Of these, 820 vehicles were referred to the secondary inspection area, where Border Patrol agents found 725 deportable aliens in 171 vehicles. In all but two cases, the aliens were discovered without a conventional search of the vehicle. A similar rate of apprehensions throughout the year would have resulted in an annual total of over 33,000, although the Government contends that many illegal aliens pass through the checkpoint undetected. The record in No. 75-5387 does not provide comparable statistical information regarding the Sarita checkpoint. While it appears that fewer illegal aliens are apprehended there, it may be assumed that fewer pass by undetected, as every motorist is questioned.
Ill
The Fourth Amendment imposes limits on search-and-seizure powers in order to prevent arbitrary and oppressive interference by enforcement officials with the privacy and personal security of individuals. See United States v. Brignoni-Ponce, 422 U. S., at 878; United States v. Ortiz, 422 U. S., at 895; Camara v. Municipal Court, 387 U. S. 523, 528 (1967). In delineating the constitutional safeguards applicable in particular contexts, the Court has weighed the public interest against the Fourth Amendment interest of the individual, United States v. Brignoni-Ponce, supra, at 878; Terry v. Ohio, 392 U. S. 1, 20-21 (1968), a process evident in our previous cases dealing with Border Patrol traffic-checking operations.
In Almeida-Sanchez v. United States, supra, the question was whether a roving-patrol unit constitutionally could search a vehicle for illegal aliens simply because it was in the general vicinity of the border. We recognized that important law enforcement interests were at stake but held that searches by roving patrols impinged so significantly on Fourth Amendment privacy interests that a search could be conducted without consent only if there was probable cause to believe that a car contained illegal aliens, at least in the absence of a judicial warrant authorizing random searches by roving patrols in a given area. Compare 413 U. S., at 273, with id., at 283-285 (Powell, J., concurring), and id., at 288 (White, J., dissenting). We held in United States v. Ortiz, supra, that the same limitations applied to vehicle searches conducted at a permanent checkpoint.
In United States v. Brignoni-Ponce, supra, however, we recognized that other traffic-checking practices involve a different balance of public and private interests and appropriately are subject to less stringent constitutional safeguards. The question was under what circumstances a roving patrol could stop motorists in the general area of the border for brief inquiry into their residence status. We found that the interference with Fourth Amendment interests involved in such a stop was “modest,” 422 U. S., at 880, while the inquiry served significant law enforcement needs. We therefore held that a roving-patrol stop need not be justified by probable cause and may be undertaken if the stopping officer is “aware of specific articulable facts, together with rational inferences from those facts, that reasonably warrant suspicion” that a vehicle contains illegal aliens. Id., at 884.
IY
It is agreed that checkpoint stops are “seizures” within the meaning of the Fourth Amendment. The defendants contend primarily that the routine stopping of vehicles at a checkpoint is invalid because Brignoni-Ponce must be read as proscribing any stops in the absence of reasonable suspicion. Sifuentes alternatively contends in No. 75-5387 that routine checkpoint stops are permissible only when the practice has the advance judicial authorization of a warrant. There was a warrant authorizing the stops at San Clemente but none at Sarita. As we reach the issue of a warrant requirement only if reasonable suspicion is not required, we turn first to whether reasonable suspicion is a prerequisite to a valid stop, a question to be resolved by balancing the interests at stake.
A
Our previous cases have recognized that maintenance of a traffic-checking program in the interior is necessary because the flow of illegal aliens cannot be controlled effectively at the border. We note here only the sub-stantiality of the public interest in the practice of routine stops for inquiry at permanent checkpoints, a practice which the Government identifies as the most important of the traffic-checking operations. Brief for United States in No. 74-1560, pp. 19-20. These checkpoints are located on important highways; in their absence such highways would offer illegal aliens a quick and safe route into the interior. Routine checkpoint inquiries apprehend many smugglers and illegal aliens who succumb to the lure of such highways. And the prospect of such inquiries forces others onto less efficient roads that are less heavily traveled, slowing their movement and making them more vulnerable to detection by roving patrols. Cf. United States v. Brignoni-Ponce, 422 U. S., at 883-885.
A requirement that stops on major routes inland always be based on reasonable suspicion would be impractical because the flow of trafile tends to be too heavy to allow the particularized study of a given car that would enable it to be identified as a possible carrier of illegal aliens. In particular, such a requirement would largely eliminate any deterrent to the conduct of well-disguised smuggling operations, even though smugglers are known to use these highways regularly.
B
While the need to make routine checkpoint stops is great, the consequent intrusion on Fourth Amendment interests is quite limited. The stop does intrude to a limited extent on motorists’ right to “free passage without interruption,’' Carroll v. United States, 267 U. S. 132, 154 (1925), and arguably on their right to personal security. But it involves only a brief detention of travelers during which
“ ‘[a] 11 that is required of the vehicle’s occupants is a response to a brief question or two and possibly the production of a document evidencing a right to be in the United States.’ ” United States v. Brignoni-Ponce, supra, at 880.
Neither the vehicle nor its occupants are searched, and visual inspection of the vehicle is limited to what can be seen without a search. This objective intrusion — the stop itself, the questioning, and the visual inspection— also existed in roving-patrol stops. But we view checkpoint stops in a different light because the subjective intrusion — the generating of concern or even fright on the part of lawful travelers — is appreciably less in the case of a checkpoint stop. In Ortiz, we noted:
“[T]he circumstances surrounding a checkpoint stop and search are far less intrusive than those attending a roving-patrol' stop. Roving patrols often operate at night on seldom-traveled roads, and their approach may frighten motorists. At traffic checkpoints the motorist can see that other vehicles are being stopped, he can see visible signs of the officers’ authority, and he is much less likely to be frightened or annoyed by the intrusion.” 422 U. S., at 894-895.
In Brignoni-Ponce, we recognized that Fourth Amendment analysis in this context also must take into account the overall degree of interference with legitimate traffic. 422 U. S., at 882-883. We concluded there that random roving-patrol stops could not be tolerated because they “would subject the residents of . . . [border] areas to potentially unlimited interference with their use of the highways, solely at the discretion of Border Patrol officers. . . . [They] could stop motorists at random for questioning, day or night, anywhere within 100 air miles of the 2,000-mile border, on a city street, a busy highway, or a desert road . . . Ibid. There also was a grave danger that such unreviewable discretion would be abused by some officers in the field. Ibid.
Routine checkpoint stops do not intrude similarly on the motoring public. First, the potential interference with legitimate traffic is minimal. Motorists using these highways are not taken by surprise as they know, or may obtain knowledge of, the location of the checkpoints and will not be stopped elsewhere. Second, checkpoint operations both appear to and actually involve less discretionary enforcement activity. The regularized manner in which established checkpoints are operated is visible evidence, reassuring to law-abiding motorists, that the stops are duly authorized and believed to serve the public interest. The location of a fixed checkpoint is not chosen by officers in the field, but by officials responsible for making overall decisions as to the most effective allocation of limited enforcement resources. We may assumg that such officials will be unlikely to locate a checkpoint where it bears arbitrarily or oppressively on motorists as a class. And since field officers may stop only those cars passing the checkpoint, there is less room for abusive or harassing stops of individuals than there was in the case of roving-patrol stops. Moreover, a claim that a particular exercise of discretion in locating or operating a checkpoint is unreasonable is subject to post-stop judicial review.
The defendants arrested at the San Clemente checkpoint suggest that its operation involves a significant extra element of intrusiveness in that only a small percentage of cars are referred to the secondary inspection area, thereby “stigmatizing” those diverted and reducing the assurances provided by equal treatment of all motorists. We think defendants overstate the consequences. Referrals are made for the sole purpose of conducting a routine and limited inquiry into residence status that cannot feasibly be made of every motorist where the traffic is heavy. The objective intrusion of the stop and inquiry thus remains minimal. Selective referral may involve some annoyance, but it remains true that the stops should not be frightening or offensive because of their public and relatively routine nature. Moreover, selective referrals — rather than questioning the occupants of every car — tend to advance some Fourth Amendment interests by minimizing the intrusion on the general motoring public.
C
The defendants note correctly that to accommodate public and private interests some quantum of individualized suspicion is usually a prerequisite to a constitutional search or seizure. See Terry v. Ohio, 392 U. S., at 21, and n. 18. But the Fourth Amendment imposes no irreducible requirement of such suspicion. This is clear from Camara v. Municipal Court, 387 U. S. 523 (1967). See also Almeida-Sanchez v. United States, 413 U. S., at 283-285 (Powell, J., concurring); id., at 288 (White, J., dissenting); Colonnade Catering Corp. v. United States, 397 U. S. 72 (1970); United States v. Biswell, 406 U. S. 311 (1972); Carroll v. United States, 267 U. S., at 154. In Camara the Court required an “area” warrant to support the reasonableness of inspecting private residences within a particular area for building code violations, but recognized that “specific knowledge of the condition of the particular dwelling” was not required to enter any given residence. 387 U. S., at 538. In so holding, the Court examined the government interests advanced to justify such routine intrusions “upon the constitutionally protected interests of the private citizen,” id., at 534—535, and concluded that under the circumstances the government interests outweighed those of the private citizen.
We think the same conclusion is appropriate here, where we deal neither with searches nor with the sanctity ' of private dwellings, ordinarily afforded the most stringent Fourth Amendment protection. See, e. g., McDonald v. United States, 335 U. S. 451 (1948). As we have noted earlier, one’s expectation of privacy in an automobile and of freedom in its operation are significantly different from the traditional expectation of privacy and freedom in one’s residence. United States v. Ortiz, 422 U. S., at 896 n. 2; see Cardwell v. Lewis, 417 U. S. 583, 590-591 (1974) (plurality opinion). And the reasonableness of the procedures followed in making these checkpoint stops makes the resulting intrusion on the interests of motorists minimal. On the other hand, the purpose of the stops is legitimate and in the public interest, and the need for this enforcement technique is demonstrated by the records in the cases before us. Accordingly, we hold that the stops and questioning at issue may be made in the absence of any individualized suspicion at reasonably located checkpoints.
We further believe that it is constitutional to refer motorists selectively to the secondary inspection area at the San Clemente checkpoint on the basis of criteria that would not sustain a roving-patrol stop. Thus, even if it be assumed that such referrals are made largely on the basis of apparent Mexican ancestry, we perceive no constitutional violation. Cf. United States v. Brignoni-Ponce, 422 U. S., at 885-887. As the intrusion here is sufficiently minimal that no particularized reason need exist to justify it, we think it follows that the Border Patrol officers must have wide discretion in selecting the motorists to be diverted for the brief questioning involved.
y
Sifuentes’ alternative argument is that routine stops at a checkpoint are permissible only if a warrant has given judicial authorization to the particular checkpoint location and the practice of routine stops. A warrant requirement in these circumstances draws some support from Camara, where the Court held that, absent consent, an “area” warrant was required to make a building code inspection, even though the search could be conducted absent cause to believe that there were violations in the building searched.
We do not think, however, that Camara is an apt model. It involved the search of private residences, for which a warrant traditionally has been required. See, e. g., McDonald v. United States, 335 U. S. 451 (1948). As developed more fully above, the strong Fourth Amendment interests that justify the warrant requirement in that context are absent here. The degree of intrusion upon privacy that may be occasioned by a search of a house hardly can be compared with the minor interference with privacy resulting from the mere stop for questioning as to residence. Moreover, the warrant requirement in Camara served specific Fourth Amendment interests to which a warrant requirement here would make little contribution. The Court there said:
“[W]hen [an] inspector [without a warrant] demands entry, the occupant has no way of knowing whether enforcement of the municipal code involved requires inspection of his premises, no way of knowing the lawful limits of the inspector’s power to search, and no way of knowing whether the inspector himself is acting under proper authorization.” 387 U. S., at 532.
A warrant provided assurance to the occupant on these scores. We believe that the visible manifestations of the field officers’ authority at a checkpoint provide substantially the same assurances in this case.
Other purposes served by the requirement of a warrant also are inapplicable here. One such purpose is to prevent hindsight from coloring the evaluation of the reasonableness of a search or seizure. Cf. United States v. Watson, 423 U. S. 411, 455-456, n. 22 (1976) (Marshall, J., dissenting). The reasonableness of checkpoint stops, however, turns on factors such as the location and method of operation of the checkpoint, factors that are not susceptible to the distortion of hindsight, and therefore will be open to post-stop review notwithstanding the absence of a warrant. Another purpose for a warrant requirement is to substitute the judgment of the magistrate for that of the searching or seizing officer. United States v. United States District Court, 407 U. S. 297, 316-318 (1972). But the need for this is reduced when the decision to “seize” is not entirely in the hands of the officer in the field, and deference is to be given to the administrative decisions of higher ranking officials.
VI
In summary, we hold that stops for brief questioning routinely conducted at permanent checkpoints are consistent with the Fourth Amendment and need not be authorized by warrant. The principal protection of Fourth Amendment rights at checkpoints lies in appropriate limitations on the scope of the stop. See Terry v. Ohio, 392 U. S., at 24—27; United States v. Brignoni-Ponce, 422 U. S., at 881-882. We have held that checkpoint searches are constitutional only if justified by consent or probable cause to search. United States v. Ortiz, 422 U. S. 891 (1975). And our holding today is limited to the type of stops described in this opinion. “[A]ny further detention . . . must be based on consent or probable cause.” United States v. Brignoni-Ponce, supra, at 882. None of the defendants in these cases argues that the stopping officers exceeded these limitations. Consequently, we affirm the judgment of the Court of Appeals for the Fifth Circuit, which had affirmed the conviction of Sifuentes. We reverse the judgment of the Court of Appeals for the Ninth Circuit and remand the case with directions to affirm the conviction of Martinez-Fuerte and to remand the other cases to the District Court for further proceedings.
It is so ordered.
The parties disagree as to whether vehicles not referred to the secondary inspection area are brought to a complete halt or merely “roll” slowly through the checkpoint. Resolution of this dispute is not necessary here, as we may assume, arguendo, that all motorists passing through the checkpoint are so slowed as to have been “seized.”
The record does not reveal explicitly why a warrant was sought. Shortly before the warrant application, however, the Court of Appeals for the Ninth Circuit had held unconstitutional a routine stop and search conducted at a permanent checkpoint without such a warrant. See United States v. Bowen, 500 F. 2d 960 (1974), aff'd on other grounds, 422 U. S. 916 (1975); United States v. Juarez-Rodriguez, 498 F. 2d 7 (1974). Soon after the warrant issued, the Court of Appeals also held unconstitutional routine checkpoint stops conducted without a warrant. See United States v. Esquer-Rivera, 500 F. 2d 313 (1974). See also n. 15, infra.
Each of the defendants in No. 74-1560 and the defendant in No. 75-5387 sought to suppress, among other things, the testimony of one or more illegal aliens. We noted in United States v. Brignoni-Ponce, 422 U. S. 873, 876 n. 2 (1975), that “[t]here may be room to question whether voluntary testimony of a witness at trial, as opposed to a Government agent’s testimony about objects seized or statements overheard, is subject to suppression . . . .” The question again is not before us.
The prosecution of Martinez-Fuerte was before a different District Judge than were the other cases.
The principal question before the Court of Appeals was the constitutional significance of the “warrant of inspection” under which the checkpoint was operating when the defendants were stopped. See n. 15, infra. The Government, however, preserved the question whether routine checkpoint stops could be made absent a warrant.
We initially granted the Government’s petition for a writ of certiorari in No. 74-1560, 423 U. S. 822, and later granted Sifuentes’ petition in No. 75-5387 and directed that the cases be argued in tandem. 423 U. S. 945. Subsequently we granted the motion of the Solicitor General to consolidate the cases for oral argument. 425 U. S. 931.
The latter occurs particularly where “border passes” are issued to simplify passage between interrelated American and Mexican communities along the border. These passes authorize travel within 25 miles of the border for a 72-hour period. See 8 CFR §212.6 (1976).
All these operations are conducted pursuant to statutory authorizations empowering Border Patrol agents to interrogate those believed to be aliens as to their right to be in the United States and to inspect vehicles for aliens. 8 U. S. C. §§ 1357 (a) (1), (a)(3). Under current regulations the authority conferred by § 1357 (a) (3) may be exercised anywhere within 100 air miles of the border. 8 CFR §287.1 (a) (1976).
As used in these statistics, the term “deportable alien” means “a person who has been found to be deportable by an immigration judge, or who admits his deportability upon questioning by official agents.” United States v. Baca, 368 F. Supp. 398, 404 (SD Cal. 1973). Most illegal aliens are simply deported without prosecution. The Government routinely prosecutes persons thought to be smugglers, many of whom are lawfully in the United States.
The Sarita checkpoint is operated a comparable proportion of the time. “Down” periods are caused by personnel shortages, weather conditions, and — at San Clemente — peak traffic loads.
On the facts of the case, we concluded that the stop was impermissible because reasonable suspicion was lacking.
The defendants argue at length that the public interest in maintaining checkpoints is l^ss than is asserted by the Government because the flow of illegal immigrants could be reduced by means other than checkpoint operations. As one alternative they suggest legislation prohibiting the knowing employment of illegal aliens. The logic of such elaborate less-restrietive-altemative arguments could raise insuperable barriers to the exercise of virtually all search-and-seizure powers. In any event, these arguments tend to go to the general proposition that all traffic-checking procedures are impermissible, a premise our previous cases reject. The defendants do not suggest persuasively that the particular law enforcement needs served by checkpoints could be met without reliance on routine checkpoint stops. Compare United States v. Brignoni-Ponce, 422 U. S., at 883 (effectiveness of roving patrols not defeated by reasonable suspicion requirement), with infra, this page.
The choice of checkpoint locations must be left largely to the discretion of Border Patrol officials, to be exercised in accordance with statutes and regulations that may be applicable. See n. 15, infra. Many incidents of checkpoint operation also must be committed to the discretion of such officials. But see infra, at 565-566.
Stops for questioning,, not dissimilar to. those involved here, are used widely at state and local levels to enforce laws regarding drivers’ licenses, safety requirements, weight limits, and similar matters. The fact that the purpose of such laws is said to be administrative is of limited relevance in weighing their intrusiveness on one’s right to travel; and the logic of the defendants’ position, if realistically pursued, might prevent enforcement officials from stopping motorists for questioning on these matters in the absence of reasonable suspicion that a law was being violated. As such laws are not before us, we intimate no view respecting them other than to note that this practice of stopping automobiles briefly for questioning has a long history evidencing its utility and is accepted by motorists as incident to highway use.
As a judicial warrant authorized the Border Patrol to malee routine stops at the San Clemente checkpoint, the principal question addressed by the Court of Appeals for the Ninth Circuit in No. 74r-1560 was whether routine checkpoint stops were constitutional when authorized by warrant. Cf. n. 5, supra. The Court of Appeals held alternatively that a warrant never could authorize such stops, 514 F. 2d 308, 318 (1975), and that it was unreasonable to issue a warrant authorizing routine stops at the San Clemente location. Id., at 321-322. In reaching the latter conclusion, the Court of Appeals relied on (i) “the [low] frequency with which illegal aliens pass through the San Clemente checkpoint,” (ii) the distance of the checkpoint from the border, and (iii) the interference with legitimate traffic. Ibid. We need not address these holdings specifically, as we conclude that no warrant is needed. But we deem the argument by the defendants in No. 74-1560 in support of the latter holding to raise the question whether, even though a warrant is not required, it is unreasonable to locate a checkpoint at San Clemente.
We answer this question in the negative. As indicated above, the choice of checkpoint locations is an administrative decision that must be left largely within the discretion of the Border Patrol, see n. 13, supra; cf. Camara v. Municipal Court, 387 U. S. 523, 538 (1967). We think the decision to locate a checkpoint at San Cle-mente was reasonable. The location meets the criteria prescribed by the Border Patrol to assure effectiveness, see supra, at 553, and the evidence supports the view that the needs of law enforcement are furthered by this location. The absolute number of apprehensions at the checkpoint is high, see supra, at 554, confirming Border Patrol judgment that significant numbers of illegal aliens regularly use Interstate 5 at this point. Also, San Clemente was selected as the location where traffic is lightest between San Diego and Los Angeles, thereby minimizing interference with legitimate traffic.
No question has been raised about the reasonableness of the location of the Sarita checkpoint. -
The Government suggests that trained Border Patrol agents rely on factors in addition to apparent Mexican ancestry when selectively diverting motorists. Brief for United States in No. 75-5387, p. 9; see United States v. Brignoni-Ponce, 422 U. S., at 884-885. This assertion finds support in the record. Less than 1% of the motorists passing the checkpoint are stopped for questioning, whereas American citizens of Mexican ancestry and legally resident Mexican citizens constitute a significantly larger proportion of the population of southern California. The 1970 census figures, which may not fully reflect illegal aliens, show the population of California to be approximately 19,958,000 of whom some 3,302,000, or 16%, are Spanish-speaking or of Spanish surname. The equivalent percentages for metropolitan San Diego and Los Angeles are 13% and 18% respectively. U. S. Department of Commerce, 1970 Census of Population, vol. 1, pt. 6, Tables 48, 140. If the statewide population ratio is applied to the approximately 146,000 vehicles passing through the checkpoint during the eight days surrounding the arrests in No. 74M560, roughly 23,400 would be expected to contain persons of Spanish or Mexican ancestry, yet only 820 were referred to the secondary area. This appears to refute any suggestion that the Border Patrol relies extensively on apparent Mexican ancestry standing alone in referring motorists to the secondary area.
Of the 820 vehicles referred to the secondary inspection area during the eight days surrounding the arrests involved in No. 74M560, roughly 20% contained illegal aliens. Supra, at 554. Thus, to the extent that the Border Patrol relies on apparent Mexican ancestry at this checkpoint, see n. 16, supra, that reliance clearly is relevant to the law enforcement need to be served. Cf. United States v. Brignoni-Ponce, supra, at 886-887, where we noted that “[tjhe likelihood that any given person of Mexican ancestry is an alien is high enough to make Mexican appearance a relevant factor although we held that apparent Mexican ancestry by itself could not create the reasonable suspicion required for a roving-patrol stop. Different considerations would arise if, for example, reliance were put on apparent Mexican ancestry at a checkpoint operated near the Canadian border.
There also is some support for a warrant requirement in the concurring and dissenting opinions in Almeida-Sanchez v. United States, 413 U. S. 266 (1973), which commanded the votes of five Justices. See id., at 283-285 (Powell, J., concurring); id., at 288 (White, J., dissenting). The burden of these opinions, however, was that an “area” warrant could serve as a substitute for the individualized probable cause to search that otherwise was necessary to sustain roving-patrol searches. As particularized suspicion is not necessary here, the warrant function discussed in Almeida-Sanchez is not an issue in these cases.
Mr. Justice Brennan’s dissenting opinion reflects unwarranted concern in suggesting that today’s decision marks a radical new intrusion on citizens’ rights: It speaks of the “evisceration of Fourth Amendment protections,” and states that the Court “virtually empties the Amendment of its reasonableness requirement.” Post, at 567, 568. Since 1952, Act of June 27, 1952, 66 Stat. 233, Congress has expressly authorized persons believed to be aliens to be interrogated as to residence, and vehicles “within a reasonable distance” from the border to be searched for aliens. See n. 8, supra. The San Clemente checkpoint has been operating at or near its present location throughout the intervening 24 years. Our prior cases have limited significantly the reach of this congressional authorization, requiring probable cause for any vehicle search in the interior and reasonable suspicion for inquiry stops by roving patrols. See supra, at 555-556. Our holding today, approving routine stops for brief questioning (a type of stop familiar to all motorists) is confined to permanent checkpoints. We understand, of course, that neither longstanding congressional authorization nor widely prevailing practice justifies a constitutional violation. We do suggest, however, that against this background and in the context of our recent decisions, the rhetoric of the dissent reflects unjustified concern.
The dissenting opinion further warns:
“Every American citizen of Mexican ancestry and every Mexican alien lawfully in this country must know after today’s decision that he travels the fixed checkpoint highways at [his] risk . . . Post, at 572.
For the reason stated in n. 16, supra, this concern is misplaced. Moreover, upon a proper showing, courts would not be powerless to prevent the misuse of checkpoints to harass those of Mexican ancestry.
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