dissenting.
The respondent William Sharpe and his passenger were pulled over to the side of the highway, concededly without probable cause, and held for more than 30 minutes, much of that time in the back seat of a police cruiser, before they ultimately were arrested and informed of the charges against them. In the meantime, the respondent Donald Savage was stopped one-half mile down the road, also according to the Court without probable cause. He was ordered out of his pickup truck at gunpoint, spread-eagled and frisked, and *703questioned by the detaining patrolman, Kenneth Thrasher, about a suspected shipment of marihuana in his vehicle. Although Savage repeatedly asked to be released, Thrasher held him for almost 15 minutes until DEA Agent Luther Cooke, the officer who had stopped Sharpe back up the road, could arrive and sniff the vehicle’s windows to determine whether he could smell the suspected marihuana. As Thrasher later conceded, Savage “was under custodial arrest” the entire time. 4 Record 165.
The Court today concludes that these lengthy detentions constituted reasonable investigative stops within the meaning of Terry v. Ohio, 392 U. S. 1 (1968). It explains that, although the length of an investigative stop made without probable cause may at some point become so excessive as to violate the Fourth Amendment, the primary inquiry must nevertheless be whether the investigating officers acted “diligently” in pursuing a stop that was no longer than “necessary” to the “legitimate investigation of the law enforcement officers.” Ante, at 687. The Court reasons that Terry’s brevity requirement is in fact an accordion-like concept that may be expanded outward depending on “the law enforcement purposes to be served by the stop.” Ante, at 685. Applying this analysis to the instant case, the Court concludes that the lengthy detentions of Sharpe and Savage were reasonable because the delay was the fault of Savage, whom the Court contends “sought to elude the police” by speeding away when signaled to stop; had Savage not taken these “evasive actions,” Agent Cooke could have questioned Sharpe and Savage together and “only.a short and certainly permissible pre-arrest detention would likely have taken place.” Ante, at 688.
I dissent. I have previously expressed my views on the permissible scope and duration of Terry stops, and need not recount those views in detail today. See, e. g., United States v. Place, 462 U. S. 696, 710 (1983) (Brennan, J., concurring in result); Kolender v. Lawson, 461 U. S. 352, 362 (1983) (Brennan, J., concurring); Florida v. Royer, 460 *704U. S. 491, 509 (1983) (Brennan, J., concurring in result). I write at some length, however, because I believe the Court’s opinion illustrates several disturbing trends in our disposition of cases involving the rights of citizens who have been accused of crime. First, the Court increasingly tends to reach out and decide issues that are not before it. If the facts in this case are as the Court recounts them, for example, the propriety of these lengthy detentions would not appear to be governed by the Terry line of cases at all, and the Court’s opinion is therefore little more than 13 pages of ill-considered dicta. Second, the Court of late shows increasing eagerness to make purely factual findings in the first instance where convenient to support its desired result. For example, the Court’s conclusion in this case that Savage “sought to elude the police” is a de novo factual determination resting on a record that is ambiguous at best. Finally, the Court in criminal cases increasingly has evaded the plain requirements of our precedents where they would stand in the way of a judgment for the government. For a Terry stop to be upheld, for example, the government must show at a minimum that the “least intrusive means reasonably available” were used in carrying out the stop. Florida v. Royer, supra, at 500 (opinion of White, J.).1 The Government has made no such showing here, and the Court’s bald assertion that “[cjlearly this case does not involve any delay unnecessary” to “legitimate” law enforcement, ante, at 687, is completely undermined by the record before us.
The Court portrays the circumstances leading up to these detentions with a studied flourish. Before Sharpe and Sav*705age were stopped, we are told, they “took evasive actions and started speeding as soon as Officer Thrasher began following them in his marked car.” Ante, at 683, n. 3. When the two were signaled to stop, Savage’s “pickup truck cut between the Pontiac and Thrasher’s patrol car, nearly hitting the patrol car, and continued down the highway.” Ante, at 678. Savage, in other words, “sought to elude the police as Sharpe moved his Pontiac to the side of the road.” Ante, at 688. As a result of Savage’s “evasive actions” and “maneuvers,” Thrasher had to chase after him and leave Agent Cooke with Sharpe, thereby laying the groundwork for the challenged delay. Ibid.
If the facts are as the Court relates them, it is not readily apparent why the Court insists on using this case as a vehicle for expanding the outer bounds of Terry investigative stops. I had thought it rather well established that where police officers reasonably suspect that an individual may be engaged in criminal activity, and the individual deliberately takes flight when the'officers attempt to stop and question him, the officers generally no longer have mere reasonable suspicion, but probable cause to arrest. See, e. g., Peters v. New York, decided together with Sibron v. New York, 392 U. S. 40, 66-67 (1968) (companion case to Terry) (“[Deliberately furtive actions and flight at the approach of strangers or law officers are strong indicia of mens rea, and when coupled with specific knowledge on the part of the officer relating the suspect to the evidence of crime, they are proper factors to be considered in the decision to make an arrest”). See also Kolender v. Lawson, supra, at 366, n. 4 (Brennan, J., concurring) (“[S]ome reactions by individuals to a properly limited Terry encounter, . . . such as flight, may often provide the necessary information, in addition to that which the officers already possess, to constitute probable cause”); Henry v. United States, 361 U. S. 98, 103 (1959) (suspicious circumstances did not ripen into probable cause because defendants’ “movements in the car had no mark of fleeing men or men *706acting furtively”); Husty v. United States, 282 U. S. 694, 701 (1931) (“prompt attempt... to escape when hailed by the officers,” when coupled with other suspicious evidence, ripened into probable cause).2
Of course, flight alone cannot give rise to probable cause; it must be coupled with pre-existing reasonable and articulable suspicion. See 1 W. LaFave, Search and Seizure §3.6, p. 669 (1978).3 And the act of flight must reasonably appear to be in response to the presence of the authorities.4 Here, *707however, the Court accepts the questionable premise that the officers already had reasonable suspicion when they decided to stop the vehicles,5 and it boldly concludes that Sharpe and Savage “started speeding” at Thrasher’s approach, that Savage “sought to elude the police” when Thrasher attempted the stop, and that Savage took “evasive actions.” Ante, at 683, n. 3, 688.
Thus if the facts were as the Court describes them, I would be inclined to view this as a probable-cause detention, and the reasonableness of these stops under Terry would not appear to be before us. The Court’s failure even to consider this question of probable cause is baffling, but ultimately in keeping with its recent practice in Terry cases of reaching out far beyond what is required to resolve the cases at hand so as more immediately to impose its views without the bother of abiding by the necessarily gradual pace of case-by-case decisionmaking. See, e. g., United States v. Place, 462 U. S., at 711, 714-720 (Brennan, J., concurring in result); Florida v. Royer, 460 U. S., at 509, 511, n. (Brennan, J., concurring in result).
II
The Court’s opinion is flawed in another critical respect: its discussion of Savage’s purported attempt “to elude the police” amounts to nothing more than a de novo factual finding made on a record that is, at best, hopelessly ambiguous. Neither the District Court nor the Court of Appeals ever found that Savage’s actions constituted evasion or flight. If we are nevertheless to engage in de novo factfinding, I *708submit the Court has taken insufficient account of several factors.
First, Savage’s actions in continuing to drive down the highway could well have been entirely consistent with those of any driver who sees the police hail someone in front of him over to the side of the road. Sharpe’s Pontiac was at least several car lengths in front of Savage’s pickup truck; Thrasher thought there was a separation of “a car length or two,” while Cooke testified that the distance was anywhere from between 30-50 and 100-150 feet. 3 Record 65; 4 id., at 139. Approaching in the far-left lane, Thrasher pulled even with Sharpe’s lead vehicle, “turned the blue light on,” “blew the siren,” and “motioned for him to pull over.” Id., at 145 (emphasis added). Savage moved into the right lane so as to avoid hitting Thrasher, who was slowing along with Sharpe, and continued on his way. Neither Cooke nor Thrasher ever testified that Savage “sought to elude” them, and there is nothing here that is necessarily inconsistent with .the actions of any motorist who happens to be behind a vehicle that is being pulled over to the side of the road.
This view of the record is strongly reinforced by Thrasher’s inability on the stand to give a responsive answer to the question: “Would you say the pickup truck was attempting to allude [sic] you or just passed you by thinking you had stopped the car?” 3 id., at 84. Thrasher replied with the nonanswer that “[w]ell, I was across . . . partially in two lanes and he got by me in the other lane,” ibid. — an observation that could be made about any motorist driving by a stop-in-progress.
Finally, the “[f]ail[ure] to stop [a] motor vehicle when signaled by [a] law-enforcement vehicle” is an independent traffic violation in South Carolina.6 Thrasher testified that *709Savage was guilty of a number of traffic violations, and when asked to specify what these violations were he enumerated that (1) Savage had been speeding through the campground, and (2) the pickup truck had improper license tags. Id., at 94-95, 99. If Savage in fact had been signaled to stop his truck and had taken “evasive actions” and “sought to elude the police,” ante, at 688,1 find it curious that Thrasher did not include these actions in his litany of Savage’s traffic offenses.
None of these factors, singularly or together, show beyond a doubt that Savage proceeded innocently past the stop of Sharpe. But given that it is the Government’s burden to prove facts justifying the duration of the investigative detention, Florida v. Royer, supra, at 500 (opinion of White, J.), and given that the courts below never found that Savage “sought to elude” the authorities,7 the Court’s conclusion to the contrary is extremely disturbing. I do not believe that citizens should be deemed to have forfeited important Fourth Amendment safeguards on the basis of a cold record as ambiguous as the one before us. Today’s opinion unfortunately is representative of a growing number of instances in which the Court is willing to make de novo factual findings in criminal cases where convenient to support its decisions.8 Even if the Court had the time and inclination to engage in the “con*710scientious and detailed examination of the record” required in fairly making purely factual judgments of this sort, United States v. Hasting, 461 U. S. 499, 517 (1983) (Stevens, J., concurring in judgment), such exercises of our authority would nevertheless be improper. The Court’s institutional role in this context should be focused on resolving “important questions of federal law” and on “ensuring clarity and uniformity of legal doctrine,” United States v. Young, ante, at 34 (Brennan, J., concurring in part and dissenting in part), rather than on serving as the prosecution’s factfinder of last resort.9
*711t — I 1 — 1 1 — 1
A
Because it has not been shown that Savage “sought to elude” the police, I agree with the Court that the constitutional propriety of these detentions is governed by Terry and its progeny. These precedents lead inexorably to the conclusion that the investigative actions at issue here violated the Fourth Amendment. As the Fourth Circuit emphasized, the lengthy detentions of Sharpe and Savage did not accord with Terry’s threshold brevity requirement. 660 F. 2d 967, 970 (1981).10 But even if the length of these detentions did not alone compel affirmance of the Fourth Circuit’s judgment, the Court today has evaded a further requirement of our Terry precedents: that “the investigative methods employed should be the least intrusive means reasonably available to *712verify or dispel the officer’s suspicion in a short period of time,” and that the Government bears the burden of demonstrating that it was objectively infeasible to investigate “in a more expeditious way.” Florida v. Royer, 460 U. S., at 500, 505 (opinion of White, J.).11 The record before us demonstrates that, for at least four reasons, the Government has not carried this burden.
First. Assuming that Savage did not break away from the officers by taking “evasive actions” to “elude” them — in which instance this is not a Terry case at all — the Government has not demonstrated why two trained law enforcement officers driving in separate vehicles, both equipped with flashing lights,12 could not have carried out a stop of a Pontiac and a pickup truck in such a manner as to ensure that both vehicles would be stopped together. Reasonable methods for bringing about the proximate stop of two vehicles readily come to mind; such methods would have been particularly important if, as the Court assumes, both officers knew that only Cooke was capable of carrying out the investigation.
Second. If the officers believed that the suspected marihuana was in Savage’s pickup truck, and if only Cooke was capable of investigating for the presence of marihuana, I am at a loss why Cooke did not follow the truck and leave Thrasher with the Pontiac, rather than vice versa.13
*713Third. The Government has offered no plausible explanation why Thrasher, a trained South Carolina highway patrolman, could not have carried out the limited Terry investigation of Savage and the pickup truck. Here again, however, the Court makes a bold de novo factual finding to the contrary:
“It was appropriate for Officer Thrasher to hold Savage for the brief period pending Cooke’s arrival. Thrasher could not be certain that he was aware of all of the facts that had aroused Cooke’s suspicions; and, as a highway patrolman, he lacked Cooke’s training and experience in dealing with narcotics investigations.” Ante, at 687, n. 5.
The record wholly undermines the Court’s conclusion. Far from being unaware of what was going on, Thrasher had conversed with Cooke by radio while they were following the vehicles and had fully discussed the various factors that might justify an investigative stop.14 Cooke sought out Thrasher’s “professional opinion” on the situation, and it was Thrasher who ultimately made the determination that they properly could stop the vehicles.15 Thrasher’s “professional opinion” was that, based on what Cooke had told him and his own observations, the truck “might be loaded” with marihuana.16 Once he had stopped Savage, Thrasher *714not only “held” him, but carried out his own investigation of the situation. He pointed out that the truck had been riding low and asked Savage what was inside. He inspected the exterior and even jumped up on the bumper to test how loaded down the camper might be. 3 Record 87; 4 id., at 150. Moreover, although Cooke certainly had more drug enforcement experience than Thrasher, there is no reason why Thrasher could not have conducted the simple sniffing investigation that Cooke later did: Thrasher, like all South Carolina highway patrolmen, had received basic narcotics detection training and knew exactly what marihuana smells like. 3 id., at 86.17 He did not even attempt to smell the windows of the camper shell for two reasons: first, that was not his assigned “job”; and second, “[m]y sinuses were stopped up that morning.” 4 id., at 164, 178; see also 3 id., at 101.18 Thrasher’s sinuses apparently cleared up several hours later, however, because once the pickup was at the police station he decided, “[j]ust as a matter of curiosity,” to “get right up on the window” of the vehicle, and reported decisively that “I smelled some marijuana up around the windows.” Ibid. I would have thought that, before the Court chose to uphold a lengthy detention of a citizen without *715probable cause based on the “reasonable” ignorance of the detaining officer, it would have taken the time to get its facts straight.19
Finally. The record strongly suggests that the delay may have been attributable in large measure to the poor investigative coordination and botched communications on the part of the DEA. Drug enforcement agents were swarming throughout the immediate area on the morning that Savage and Sharpe were detained, conducting numerous roadblocks and “profile stops” of campers and recreational vehicles similar to Savage’s. See n. 9, supra. Even accepting the Court’s dubious premise that a highway patrolman is somehow incapable of carrying out a simple investigative stop, it is clear that Cooke had followed Sharpe and Savage for over 30 minutes and, knowing that a multiple-vehicle stop was in the offing, should have obtained assistance from other DEA agents. This was, in fact, precisely what he attempted to do. He repeatedly tried to contact the area DEA headquarters but complained over his police radio that “I can’t raise anybody else right now.” Defendant’s Ex. 1, p. 3 (police-*716band transcription). He asked the local police dispatcher to telephone the DEA office to “ask them if anybody there has any contact with me on my DEA frequency.” Id., at 4. The dispatcher reported that the line was busy; local police units had to be sent out to headquarters “to tell these people to get off the telephone.” Id., at 6. Once the units arrived, it was learned that “[tjhere’s no one there. They’re all down at the Mar Vista Motel.” Ibid. Additional units had to be sent to the motel to “get those people out of the sack.” Ibid. Agents apparently were eventually located at the motel and at Don’s Pancake House, ibid.,' for by the time that Cooke returned to the Pontiac to complete the arrests there were several other DEA agents waiting to assist him, 4 Record 171-172. In the meantime, of course, Cooke had had to request Thrasher as a local backup.
Far from demonstrating that these investigative stops were carried out in the most “expeditious way” using all “reasonably available” investigative methods, Florida v. Royer, 460 U. S., at 500, 505 (opinion of White, J.), the record in this case therefore strongly suggests custodial detentions more accurately characterized as resulting from hopelessly bungled communications and from Thrasher’s unwillingness to tread on Cooke’s investigative turf. I do not mean to suggest that Cooke and Thrasher bore the entire blame for these delays; it was not Cooke’s fault that his DEA backups apparently were sleeping or eating breakfast rather than monitoring their radios for his calls, and Thrasher might well have felt that it was not his place to carry out an investigation he apparently was fully capable of conducting. But constitutional rights should not so easily be balanced away simply because the individual officers may have subjectively been acting in good faith, especially where an objective evaluation of the facts suggests an unnecessarily intrusive exercise of police power.20
*717B
We must remember the Fourth Amendment values at stake here. The Framers understood that “[uncontrolled search and seizure is one of the first and most effective weapons in the arsenal of every arbitrary government,” and that “[a]mong deprivations of rights, none is so effective in cowing a population, crushing the spirit of the individual and putting terror in every heart.” Brinegar v. United States, 338 U. S. 160, 180 (1949) (Jackson, J., dissenting). The Framers accordingly provided that individuals shall be arrested and detained only on probable cause — a standard with “roots that are deep in our history,” Henry v. United States, 361 U. S., at 100, and grounded on “a practical, nontechnical conception affording the best compromise that has been found for accommodating” the “often opposing” interests of effective law enforcement and individual rights, Brinegar v. United States, supra, at 176. By requiring that arrests be made only on probable cause, the Framers sought to preclude custodial *718detentions resulting solely from “common rumor or report, suspicion, or even ‘strong reason to suspect.”’ Henry v. United States, supra, at 101. Terry and its progeny depart from the probable-cause safeguard, but only because the sorts of limited intrusions wrought by such encounters fall “far short of the kind of intrusion associated with an arrest.” Dunaway v. New York, 442 U. S. 200, 212 (1979). Detaining officers therefore may briefly question individuals and “ask them to explain suspicious circumstances, but any further detention or search must be based on consent or probable cause.” United States v. Brignoni-Ponce, 422 U. S. 873, 882 (1975) (emphasis added).
Terry’s brevity requirement thus functions as an important constitutional safeguard that prevents an investigative stop from being transformed into a custodial detention merely because “the law enforcement purposes to be served by the stop” are considered important. Ante, at 685. Absent a rigorously enforced brevity requirement, the Terry rationale “would threaten to swallow the general rule that Fourth Amendment seizures are ‘reasonable’ only if based on probable cause.” Dunaway v. New York, supra, at 212-213. As Justice Marshall cogently discusses today, the brevity requirement also serves to compel law enforcement agencies to “structure their Terry encounters” by employing the resources and methods necessary to “minimize the intrusions worked by these encounters.” Ante, at 693 (concurring in judgment). Similarly, Royer’s requirement that the prosecution demonstrate that the Terry stop was carried out in the most “expeditious way” using all “reasonably available” investigative methods, 460 U. S., at 500, 505 (opinion of White, J.), operates to ensure that law enforcement agencies commit the manpower, training, and resources necessary to guarantee that investigative detentions are carried out in the least intrusive manner possible. Some may protest that such requirements impede unduly on law enforcement, but surely these are reasonable tradeoffs for the authority to *719seize and detain citizens on less than probable cause. And while it may be tempting to relax these requirements when a defendant is believed to be guilty, the standards we prescribe for the guilty define the authority of the police in detaining the innocent as well. Cf. Brinegar v. United States, supra, at 181 (Jackson, J., dissenting) (“[A] search against Brinegar’s car must be regarded as a search of the car of Everyman”).
In this connection, I am particularly disturbed by the Court’s suggestion that it might be constitutionally reasonable for a highway patrolman to hold a motorist on Terry suspicion pending the arrival of an officer with more “training and experience.” Ante, at 687, n. 5. The Court is of course correct in emphasizing that Cooke was much more expert at drug detection than Thrasher. I can imagine a great many roadside stop situations in which it might make good police sense for the detaining officer to hold the motorist indefinitely without probable cause so that the officer could have an expert interrogator drive out from the city to conduct the “brief” questioning authorized by Terry, or so that his more experienced sergeant could be summoned to render a second opinion, or so that a trained narcotics dog owned by the adjacent county could be driven out to sniff around the windows. I can also imagine circumstances where, given the limited number of patrol cars in a community, an officer might prefer to handcuff a person stopped for investigative questioning to a lamppost while the officer responded to an emergency call.. All of these actions might be preferable from a law enforcement standpoint. The Framers did not enact the Fourth Amendment to further the investigative powers of the authorities, however, but to curtail them: Terry’s exception to the probable-cause safeguard must not be expanded to the point where the constitutionality of a citizen’s detention turns only on whether the individual officers were coping as best they could given inadequate training, .marginal resources, negligent supervision, or botched communications. *720Our precedents require more — the demonstration by the Government that it was infeasible to conduct the training, ensure the smooth communications, and commit the sort of resources that would have minimized the intrusions. United States v. Place, 462 U. S., at 709-710; Florida v. Royer, 460 U. S., at 505-606 (opinion of White, J.).
The Court today has evaded these requirements, failed even to acknowledge the evidence of bungling, miscommuni-cation, and reasonable investigative alternatives, and pronounced simply that the individual officers “acted diligently.” Ante, at 688. Thus the Court has moved a step or two further in what appears to be “an emerging tendency on the part of the Court to convert the Terry decision into a general statement that the Fourth Amendment requires only that any seizure be reasonable,” United States v. Place, supra, at 721 (Blackmun, J., concurring in judgment) — a balancing process in which the judicial thumb apparently will be planted firmly on the law enforcement side of the scales.21
>
Justice Douglas, the lone dissenter m Terry, warned that “[t]here have been powerful hydraulic pressures throughout our history that bear heavily on the Court to water down constitutional guarantees and give the police the upper hand.” 392 U. S., at 39. Those hydraulic pressures are readily apparent in the outcome of this case. The Court has eschewed narrow grounds of decision so as to expand the bounds of Terry; engaged in questionable de novo factfinding in violation of its proper mission; either ignored or misconstrued numerous factors in the record that call into question the reasonableness of these custodial detentions; and evaded the *721requirements of squarely governing precedents. This breed of decisionmaking breaches faith with our high constitutional duty “to prevent wholesale intrusions upon the personal security of our citizenry.” Davis v. Mississippi, 394 U. S. 721, 726 (1969). I dissent.
Concurring in the plurality’s result in Royer, I argued that the Fourth Amendment requires an even more stringent standard: “a lawful stop must be so strictly limited that it is difficult to conceive of a less intrusive means that would be effective to accomplish the purpose of the stop.” 460 U. S., at 511. n.
See generally 1 W. LaFave, Search and Seizure §3.6, p. 669 (1978) (“[I]f there already exists a significant degree of suspicion concerning a particular person, the flight of that individual upon the approach of the police may be taken into account and may well elevate the pre-existing suspicion up to the requisite Fourth Amendment level of probable cause”). Representative federal and state cases applying this principle include United States v. Martinez-Gonzalez, 686 F. 2d 93, 100 (CA2 1982) (“The event that transformed the agents’ reasonable suspicion into probable cause was Martinez’s own manifestation of guilt evidenced by his flight from the agents back into the apartment when the agents approached him to talk to him”); United States v. Green, 216 U. S. App. D. C. 329, 333-334, 670 F. 2d 1148, 1152-1153 (1981); United States v. Gomez, 633 F. 2d 999, 1007-1008 (CA2 1980), cert. denied, 450 U. S. 994 (1981); United States v. Vasquez, 534 F. 2d 1142,1145-1146 (CA5), cert. denied, 429 U. S. 979 (1976); People v. Amick, 36 Cal. App. 3d 140, 144-145, 111 Cal. Rptr. 280, 282-283 (1973); People v. Holdman, 73 Ill. 2d 213, 221-222, 383 N. E. 2d 155, 158-159 (1978), cert. denied, 440 U. S. 938 (1979); Commonwealth v. Ortiz, 376 Mass. 349, 353-354, 380 N. E. 2d 669, 673 (1978); People v. Kreichman, 37 N. Y. 2d 693, 698-699, 339 N. E. 2d 182, 187-188 (1975) (attempt to stop vehicle on' reasonable suspicion, followed by 14-bloek chase, created probable cause); Commonwealth v. Dennis, 236 Pa. Super. 348, 351, 344 A. 2d 713, 715 (1975).
“Were it otherwise, ‘anyone who does not desire to talk to the police and who either walks or runs away from them would always be subject to legal arrest,’ which can hardly ‘be countenanced under the Fourth and Fourteenth Amendments.’” 1 LaFave, supra, at 669, quoting United States v. Margeson, 259 F. Supp. 256, 265 (ED Pa. 1966).
Compare Wong Sun v. United States, 371 U. S. 471, 482 (1963) (“[W]hen an officer insufficiently or unelearly identifies his office or his mission, the occupant’s flight from the door must be regarded as ambiguous conduct”), with People v. Amick, supra, at 145, 111 Cal. Rptr., at 283 *707(“[The police] had a right to and did assume that at that time [the driver and his passengers] knew law enforcement officials wanted to talk to them; and upon being pursued by the black and white unit and Officer Kapphahn with red spotlight and siren there could be little doubt that [the occupants] knew they were being pursued by officers although they failed to stop and continued for a quarter of a mile until they were forced to stop”).
See n. 9, infra.
South Carolina Code § 56-5-750 (1976) provides: “It shall be unlawful for any motor vehicle driver, while driving on any road, street or highway of the State, to fail to stop when signaled by any law-enforcement vehicle by means of a siren or flashing light. Any attempt to increase the speed of a vehicle or in other manner avoid the pursuing law-enforcement vehicle *709when signaled by a siren or flashing light shall constitute prima facie evidence of a violation of this section. ...”
The Court of Appeals did not discuss this issue one way or the other. The closest that the District Court came to passing on the question was an ambiguous statement during a colloquy that the stop “took a little longer than it should have taken. They created their own problem.” 4 Record 221. The court’s reference to “they” arguably could have been to Sharpe and Savage, but such a construction is tenuous given the court’s previous comment that the stop took longer “than it should have taken” — which seems to be addressed to the actions of the officers. The Government quite properly has never sought to distill from this ambiguous remark a “finding” that Savage took “evasive actions” or “sought to elude the police.”
See, e. g., Oregon v. Elstad, ante, at 360-362 (Brennan, J., dissenting); United States v. Young, ante, at 30-35 (Brennan, J., concurring in *710part and dissenting in part); United States v. Hasting, 461 U. S. 499, 516-519 (1983) (Stevens, J., concurring in judgment).
Like Justice Marshall, ante, at 700-702 (concurring in judgment), I cannot understand why the Court feels compelled to decide that the District Court’s finding of reasonable suspicion “is abundantly supported by the record,” ante, at 682. The Court of Appeals merely assumed that the reasonable-suspicion finding was proper for the sake of analysis, 660 F. 2d 967, 970 (CA4 1981), and the question was not presented for our consideration. The District Court considered the issue “a real close question,” emphasized its “great reluctance” on the merits, and found that the Government had barely established reasonable suspicion “by the greater weight of the evidence” but that it had not shown sufficient suspicion beyond a reasonable doubt. 5 Record 152-155, 190.
The Court has taken insufficient account of several factors. First, these detentions were little more than “profile stops” similar to numerous stops of campers and recreational vehicles carried out by the DEA in the general area on the day in question; none of these other questionable profile stops turned up any evidence of wrongdoing. 4 id., at 126-127, 190. See also 3 id., at 70-71 (DEA “set up roadblocks in that particular area and did stop a number of vehicles with roadblocks”). Second, there is nothing in the record to support the Court’s assertion that Sharpe and Savage “started speeding as soon as Officer Thrasher began following them in his marked car.” Ante, at 683, n. 3; see ante, at 701 (Marshall, J., concurring in judgment). To the extent the Court suggests that they were attempting to speed away at Thrasher’s approach, this factual finding is inconsistent with Thrasher’s concession that Sharpe and Savage stopped at every stop sign and traffic light they encountered — lawful conduct that hardly comports with notions of a high-speed attempt to elude the authorities. 4 *711Record 142-143. Finally, it appears strongly that the reason these profile stops were made when they were was not because Cooke’s “reasonable” suspicions had hardened, but because he was about to run out of gas. See Defendant’s Ex. 1, pp. 4-5 (Cooke’s discussion with Thrasher over police radio) (“We’re going to have to do it pretty quick or I’ll have to go 10-7 for gas! . . . You want to just try to run them into there? I’d like to take the Pontiac in there with it, I don’t have anything to go on on it other than just normal suspicion. I’d like to at least I.D. the driver and passenger in that”). As the District Court perceptively observed, “[i]t’s possibly [sic] the very basic reason for stopping them was because Mr. Cooke was about to run out of gas.” 5 Record 52.
The Fourth Circuit held that “the length of the detentions effectively transformed them into de facto arrests without bases in probable cause, unreasonable seizures under the Fourth Amendment.” 660 F. 2d, at 970. Officer Thrasher himself conceded that Savage was under “custodial arrest” during the entire stop. 4 Record 165. Far from being merely “the brief and narrowly circumscribed intrusions” authorized by the Terry line of authority, the detentions here were “in important respects indistinguishable from a traditional arrest,” and “any ‘exception’ that could cover a seizure as intrusive as that in this case would threaten to swallow the general rule that Fourth Amendment seizures are ‘reasonable’ only if based on probable cause.” Dunaway v. New York, 442 U. S. 200, 212-213 (1979). See also ante, at 696-698 (Marshall, J., concurring in judgment).
As I have previously argued, I do not believe that “the absence of a less intrusive means can make an otherwise unreasonable stop reasonable.” Florida v. Royer, 460 U. S., at 511, n. (concurring in result). See also n. 1, supra.
Thrasher was driving a marked police car, and Cooke’s unmarked vehicle carried a portable flashing light that could be attached to the dash. See 4 Record 54.
On the stand, the officers disagreed as to which one of them was responsible for this questionable decision. Cooke, supposedly the officer in charge, insisted that “Thrasher told me to get the Pontiac.” Ibid. Thrasher, on the other hand, maintained that “Cooke said he would stay with the Pontiac.” Id., at 145. The Conway Highway Patrol Dispatch Communications transcript demonstrates that Thrasher told Cooke to “[t]ake the Pontiac, I’ll get the truck.” Defendant’s Ex. 1, p. 5.
See, e. g., id., at 3-4 (transcription of police-band exchanges) (discussing known offloading of marihuana during the night, vehicles’ movements, and appearance of vehicles); 4 Record 50 (Cooke “conversed with Mr. Thrasher and attempted to tell him what I had encountered, where I had been”); id., at 52-53, 159-161.
Cooke asked: “What’s your professional opinion of the way that truck’s riding?” Thrasher responded: “He’s loaded. He’s got a load in there of something.” Cooke replied: “Is that enough reason for you to stop him?” Thrasher answered: “Affirmative . . . Just say the word and I’ll . . . .” Defendant’s Ex. 1, p. 4. See also 4 Record 52-53.
3 id., at 87 (Thrasher “suspected that [the truck] may have marihuana in it” because “the camper windows were covered” with quilts and camper appeared to be overloaded); 4 id., at 160-161 (Thrasher knew the truck was suspected of carrying marihuana).
The Fourth Circuit assumed without deciding that “the odor of raw marijuana may provide probable cause to search a vehicle legitimately stopped.” 660 F. 2d, at 971. As Justice Marshall notes, “[n]o question is presented [in this case] as to whether odor that creates probable cause also justifies a warrantless search.” Ante, at 699, n. 12 (concurring in judgment). See United States v. Johns, 469 U. S. 478, 489 (1985) (Brennan, J., dissenting).
After Cooke claimed to have smelled the marijuana, Savage asked for Thrasher’s opinion. See 4 Record 177 (“Q. Don’t you remember . . . Don Savage saying [to Cooke] you don’t smell any marijuana, let’s get a second opinion from this officer here, don’t you remember that, talking about you, getting your second opinion? A. Yes, sir, I believe he might have”). Thrasher could not recall why he did not follow through on the request. Id., at 177-178.
The Court has responded by insisting that Thrasher “could not be certain that he was aware” of all the facts and therefore was justified in detaining Savage indefinitely. Ante, at 687, n. 5. The Court has not pointed to anything that would support this bald de novo finding, which is squarely contradicted by the record. See supra, at 713-714. In addition, the Court’s reasoning flies directly in the face of the Fourth Amendment, which requires the authorities to ground their conduct on what is known at the time of their actions rather than on what might subsequently turn up. See, e. g., Henry v. United States, 361 U. S. 98, 103 (1959) (“An arrest is not justified by what the subsequent search discloses”); Johnson v. United States, 333 U. S. 10, 17 (1948). The Court’s unprecedented suggestion to the contrary threatens to “obliterate one of the most fundamental distinctions between our form of government, where officers are under the law, and the police-state where they are the law.” Ibid. It is enough here that Thrasher possessed whatever reasonable suspicion Cooke did and was fully in the position to conduct the sniffing investigation that Cooke later undertook.
In response to this dissent, the Court offers several justifications for its failure to consult the record in making its de novo factual determina*717tions. First, the Court asserts that judges “should not indulge in unrealistic second-guessing” of police conduct. Ante, at 686. There is nothing “unrealistic” about requiring police officers to pursue the “least intrusive means reasonably available” when detaining citizens on less than probable cause, Florida v. Royer, 460 U. S., at 500 (opinion of White, J.), and it is the duty of courts in every Fourth Amendment case to determine whether police conduct satisfied constitutional standards. Moreover, the public will understandably be perplexed why the Court ignores the record and refuses to engage in “second-guessing” where police conduct is challenged while it simultaneously engages in second-guessing of a defendant’s conduct where necessary to ensure a verdict for the Government.
In addition, the Court attempts to slip into a footnote the astonishing assertion that even if its textual discussion of Savage’s actions is completely untrue, this “would not alter our analysis or our conclusion.” Ante, at 688, n. 6 (emphasis added). The Court contends that, “whether innocent or purposeful,” Savage’s conduct “made . . . necessary” the length of these detentions. Ibid, (emphasis added). If the authorities did not reasonably carry out the stops, however, and if Savage’s continued driving was “innocent” conduct, ibid., it is logically and constitutionally intolerable to hold that Savage waived important Fourth Amendment rights because the events were his “innocent” fault.
Cf. United States v. Leon, 468 U. S. 897, 929 (1984) (Brennan, J., dissenting) (noting Court’s increasing resort to cost/benefit analyses “where the ‘costs’ of excluding illegally obtained evidence loom to exaggerated heights and where the ‘benefits’ of such exclusion are made to disappear with a mere wave of the hand”).