Skinner v. Railway Labor Executives' Assn.
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Full Opinion
SKINNER, SECRETARY OF TRANSPORTATION, ET AL.
v.
RAILWAY LABOR EXECUTIVES' ASSOCIATION ET AL.
Supreme Court of United States.
*605 Attorney General Thornburgh argued the cause for petitioners. On the briefs were Solicitor General Fried, Assistant Attorney General Bolton, Deputy Solicitor General Merrill, Deputy Assistant Attorneys General Spears and Cynkar, Lawrence S. Robbins, Leonard Schaitman, Marc Richman, B. Wayne Vance, S. Mark Lindsey, and Daniel Carey Smith.
Lawrence M. Mann argued the cause for respondents. With him on the brief were W. David Holsberry, Harold A. Ross, and Clinton J. Miller III.[*]
Briefs of amici curiae urging affirmance were filed for the American Civil Liberties Union et al. by James D. Holzhauer, John A. Powell, Stephen R. Shapiro, Harvey Grossman, and Edward M. Chen; and for the American Federation of Labor and Congress of Industrial Organizations by David Silberman and Laurence Gold.
Scott D. Raphael filed a brief for the Aircraft Owners & Pilots Association as amicus curiae.
*606 JUSTICE KENNEDY delivered the opinion of the Court.
The Federal Railroad Safety Act of 1970 authorizes the Secretary of Transportation to "prescribe, as necessary, appropriate rules, regulations, orders, and standards for all areas of railroad safety." 84 Stat. 971, 45 U. S. C. § 431(a). Finding that alcohol and drug abuse by railroad employees poses a serious threat to safety, the Federal Railroad Administration (FRA) has promulgated regulations that mandate blood and urine tests of employees who are involved in certain train accidents. The FRA also has adopted regulations that do not require, but do authorize, railroads to administer breath and urine tests to employees who violate certain safety rules. The question presented by this case is whether these regulations violate the Fourth Amendment.
I
A
The problem of alcohol use on American railroads is as old as the industry itself, and efforts to deter it by carrier rules began at least a century ago. For many years, railroads have prohibited operating employees from possessing alcohol or being intoxicated while on duty and from consuming alcoholic beverages while subject to being called for duty. More recently, these proscriptions have been expanded to forbid possession or use of certain drugs. These restrictions are *607 embodied in "Rule G," an industry-wide operating rule promulgated by the Association of American Railroads, and are enforced, in various formulations, by virtually every railroad in the country. The customary sanction for Rule G violations is dismissal.
In July 1983, the FRA expressed concern that these industry efforts were not adequate to curb alcohol and drug abuse by railroad employees. The FRA pointed to evidence indicating that on-the-job intoxication was a significant problem in the railroad industry.[1] The FRA also found, after a review of accident investigation reports, that from 1972 to 1983 "the nation's railroads experienced at least 21 significant train accidents involving alcohol or drug use as a probable cause or contributing factor," and that these accidents "resulted in 25 fatalities, 61 non-fatal injuries, and property damage estimated at $19 million (approximately $27 million in 1982 dollars)." 48 Fed. Reg. 30726 (1983). The FRA further identified "an additional 17 fatalities to operating employees working on or around rail rolling stock that involved alcohol or drugs as a contributing factor." Ibid. In light of these problems, the FRA solicited comments from interested parties on a various regulatory approaches to the problems of alcohol and drug abuse throughout the Nation's railroad system.
Comments submitted in response to this request indicated that railroads were able to detect a relatively small number of Rule G violations, owing, primarily, to their practice of *608 relying on observation by supervisors and co-workers to enforce the rule. 49 Fed. Reg. 24266-24267 (1984). At the same time, "industry participants . . . confirmed that alcohol and drug use [did] occur on the railroads with unacceptable frequency," and available information from all sources "suggest[ed] that the problem includ[ed] `pockets' of drinking and drug use involving multiple crew members (before and during work), sporadic cases of individuals reporting to work impaired, and repeated drinking and drug use by individual employees who are chemically or psychologically dependent on those substances." Id., at 24253-24254. "Even without the benefit of regular post-accident testing," the FRA "identified 34 fatalities, 66 injuries and over $28 million in property damage (in 1983 dollars) that resulted from the errors of alcohol and drug-impaired employees in 45 train accidents and train incidents during the period 1975 through 1983." Id., at 24254. Some of these accidents resulted in the release of hazardous materials and, in one case, the ensuing pollution required the evacuation of an entire Louisiana community. Id., at 24254, 24259. In view of the obvious safety hazards of drug and alcohol use by railroad employees, the FRA announced in June 1984 its intention to promulgate federal regulations on the subject.
B
After reviewing further comments from representatives of the railroad industry, labor groups, and the general public, the FRA, in 1985, promulgated regulations addressing the problem of alcohol and drugs on the railroads. The final regulations apply to employees assigned to perform service subject to the Hours of Service Act, ch. 2939, 34 Stat. 1415, as amended, 45 U. S. C. § 61 et seq. The regulations prohibit covered employees from using or possessing alcohol or any controlled substance. 49 CFR § 219.101(a)(1) (1987). The regulations further prohibit those employees from reporting for covered service while under the influence of, or *609 impaired by, alcohol, while having a blood alcohol concentration of 0.04 or more, or while under the influence of, or impaired by, any controlled substance. § 219.101(a)(2). The regulations do not restrict, however, a railroad's authority to impose an absolute prohibition on the presence of alcohol or any drug in the body fluids of persons in its employ, § 219.101(c), and, accordingly, they do not "replace Rule G or render it unenforceable." 50 Fed. Reg. 31538 (1985).
To the extent pertinent here, two subparts of the regulations relate to testing. Subpart C, which is entitled "Post-Accident Toxicological Testing," is mandatory. It provides that railroads "shall take all practicable steps to assure that all covered employees of the railroad directly involved . . . provide blood and urine samples for toxicological testing by FRA," § 219.203(a), upon the occurrence of certain specified events. Toxicological testing is required following a "major train accident," which is defined as any train accident that involves (i) a fatality, (ii) the release of hazardous material accompanied by an evacuation or a reportable injury, or (iii) damage to railroad property of $500,000 or more. § 219.201 (a)(1). The railroad has the further duty of collecting blood and urine samples for testing after an "impact accident," which is defined as a collision that results in a reportable injury, or in damage to railroad property of $50,000 or more. § 219.201(a)(2). Finally, the railroad is also obligated to test after "[a]ny train incident that involves a fatality to any on-duty railroad employee." § 219.201(a)(3).
After occurrence of an event which activates its duty to test, the railroad must transport all crew members and other covered employees directly involved in the accident or incident to an independent medical facility, where both blood and urine samples must be obtained from each employee.[2] After *610 the samples have been collected, the railroad is required to ship them by prepaid air freight to the FRA laboratory for analysis. § 219.205(d). There, the samples are analyzed using "state-of-the-art equipment and techniques" to detect and measure alcohol and drugs.[3] The FRA proposes to place primary reliance on analysis of blood samples, as blood is "the only available body fluid . . . that can provide a clear indication not only of the presence of alcohol and drugs but also their current impairment effects." 49 Fed. Reg. 24291 (1984). Urine samples are also necessary, however, because drug traces remain in the urine longer than in blood, and in some cases it will not be possible to transport employees to a medical facility before the time it takes for certain drugs to be eliminated from the bloodstream. In those instances, a "positive urine test, taken with specific information on the pattern of elimination for the particular drug and other information on the behavior of the employee and the circumstances of the accident, may be crucial to the determination of" the cause of an accident. Ibid.
The regulations require that the FRA notify employees of the results of the tests and afford them an opportunity to respond in writing before preparation of any final investigative report. See § 219.211(a)(2). Employees who refuse to provide required blood or urine samples may not perform covered *611 service for nine months, but they are entitled to a hearing concerning their refusal to take the test. § 219.213.
Subpart D of the regulations, which is entitled "Authorization to Test for Cause," is permissive. It authorizes railroads to require covered employees to submit to breath or urine tests in certain circumstances not addressed by Subpart C. Breath or urine tests, or both, may be ordered (1) after a reportable accident or incident, where a supervisor has a "reasonable suspicion" that an employee's acts or omissions contributed to the occurrence or severity of the accident or incident, § 219.301(b)(2); or (2) in the event of certain specific rule violations, including noncompliance with a signal and excessive speeding, § 219.301(b)(3). A railroad also may require breath tests where a supervisor has a "reasonable suspicion" that an employee is under the influence of alcohol, based upon specific, personal observations concerning the appearance, behavior, speech, or body odors of the employee. § 219.301(b)(1). Where impairment is suspected, a railroad, in addition, may require urine tests, but only if two supervisors make the appropriate determination, § 219.301(c)(2)(i), and, where the supervisors suspect impairment due to a substance other than alcohol, at least one of those supervisors must have received specialized training in detecting the signs of drug intoxication, § 219.301(c)(2)(ii).
Subpart D further provides that whenever the results of either breath or urine tests are intended for use in a disciplinary proceeding, the employee must be given the opportunity to provide a blood sample for analysis at an independent medical facility. § 219.303(c). If an employee declines to give a blood sample, the railroad may presume impairment, absent persuasive evidence to the contrary, from a positive showing of controlled substance residues in the urine. The railroad must, however, provide detailed notice of this presumption to its employees, and advise them of their right to provide a contemporaneous blood sample. As in the case of samples procured under Subpart C, the regulations set forth *612 procedures for the collection of samples, and require that samples "be analyzed by a method that is reliable within known tolerances." § 219.307(b).
C
Respondents, the Railway Labor Executives' Association and various of its member labor organizations, brought the instant suit in the United States District Court for the Northern District of California, seeking to enjoin the FRA's regulations on various statutory and constitutional grounds. In a ruling from the bench, the District Court granted summary judgment in petitioners' favor. The court concluded that railroad employees "have a valid interest in the integrity of their own bodies" that deserved protection under the Fourth Amendment. App. to Pet. for Cert. 53a. The court held, however, that this interest was outweighed by the competing "public and governmental interest in the . . . promotion of. . . railway safety, safety for employees, and safety for the general public that is involved with the transportation." Id., at 52a. The District Court found respondents' other constitutional and statutory arguments meritless.
A divided panel of the Court of Appeals for the Ninth Circuit reversed. Railway Labor Executives' Assn. v. Burnley, 839 F. 2d 575 (1988). The court held, first, that tests mandated by a railroad in reliance on the authority conferred by Subpart D involve sufficient Government action to implicate the Fourth Amendment, and that the breath, blood, and urine tests contemplated by the FRA regulations are Fourth Amendment searches. The court also "agre[ed] that the exigencies of testing for the presence of alcohol and drugs in blood, urine or breath require prompt action which precludes obtaining a warrant." Id., at 583. The court further held that "accommodation of railroad employees' privacy interest with the significant safety concerns of the government does not require adherence to a probable cause requirement," and, accordingly, that the legality of the searches contemplated by *613 the FRA regulations depends on their reasonableness under all the circumstances. Id., at 587.
The court concluded, however, that particularized suspicion is essential to a finding that toxicological testing of railroad employees is reasonable. Ibid. A requirement of individualized suspicion, the court stated, would impose "no insuperable burden on the government," id., at 588, and would ensure that the tests are confined to the detection of current impairment, rather than to the discovery of "the metabolites of various drugs, which are not evidence of current intoxication and may remain in the body for days or weeks after the ingestion of the drug." Id., at 588-589. Except for the provisions authorizing breath and urine tests on a "reasonable suspicion" of drug or alcohol impairment, 49 CFR §§ 219.301(b)(1) and (c)(2) (1987), the FRA regulations did not require a showing of individualized suspicion, and, accordingly, the court invalidated them.
Judge Alarcon dissented. He criticized the majority for "fail[ing] to engage in [a] balancing of interests" and for focusing instead "solely on the degree of impairment of the workers' privacy interests." 839 F. 2d, at 597. The dissent would have held that "the government's compelling need to assure railroad safety by controlling drug use among railway personnel outweighs the need to protect privacy interests." Id., at 596.
We granted the federal parties' petition for a writ of certiorari, 486 U. S. 1042 (1988), to consider whether the regulations invalidated by the Court of Appeals violate the Fourth Amendment. We now reverse.
II
The Fourth Amendment provides that "[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated . . . ." The Amendment guarantees the privacy, dignity, and security of persons against certain arbitrary *614 and invasive acts by officers of the Government or those acting at their direction. Camara v. Municipal Court of San Francisco, 387 U. S. 523, 528 (1967). See also Delaware v. Prouse, 440 U. S. 648, 653-654 (1979); United States v. Martinez-Fuerte, 428 U. S. 543, 554 (1976). Before we consider whether the tests in question are reasonable under the Fourth Amendment, we must inquire whether the tests are attributable to the Government or its agents, and whether they amount to searches or seizures. We turn to those matters.
A
Although the Fourth Amendment does not apply to a search or seizure, even an arbitrary one, effected by a private party on his own initiative, the Amendment protects against such intrusions if the private party acted as an instrument or agent of the Government. See United States v. Jacobsen, 466 U. S. 109, 113-114 (1984); Coolidge v. New Hampshire, 403 U. S. 443, 487 (1971). See also Burdeau v. McDowell, 256 U. S. 465, 475 (1921). A railroad that complies with the provisions of Subpart C of the regulations does so by compulsion of sovereign authority, and the lawfulness of its acts is controlled by the Fourth Amendment. Petitioners contend, however, that the Fourth Amendment is not implicated by Subpart D of the regulations, as nothing in Subpart D compels any testing by private railroads.
We are unwilling to conclude, in the context of this facial challenge, that breath and urine tests required by private railroads in reliance on Subpart D will not implicate the Fourth Amendment. Whether a private party should be deemed an agent or instrument of the Government for Fourth Amendment purposes necessarily turns on the degree of the Government's participation in the private party's activities, cf. Lustig v. United States, 338 U. S. 74, 78-79 (1949) (plurality opinion); Byars v. United States, 273 U. S. 28, 32-33 (1927), a question that can only be resolved "in light of all the circumstances," Coolidge v. New Hampshire, supra, *615 at 487. The fact that the Government has not compelled a private party to perform a search does not, by itself, establish that the search is a private one. Here, specific features of the regulations combine to convince us that the Government did more than adopt a passive position toward the underlying private conduct.
The regulations, including those in Subpart D, pre-empt state laws, rules, or regulations covering the same subject matter, 49 CFR § 219.13(a) (1987), and are intended to supersede "any provision of a collective bargaining agreement, or arbitration award construing such an agreement," 50 Fed. Reg. 31552 (1985). They also confer upon the FRA the right to receive certain biological samples and test results procured by railroads pursuant to Subpart D. § 219.11(c). In addition, a railroad may not divest itself of, or otherwise compromise by contract, the authority conferred by Subpart D. As the FRA explained, such "authority . . . is conferred for the purpose of promoting the public safety, and a railroad may not shackle itself in a way inconsistent with its duty to promote the public safety." 50 Fed. Reg. 31552 (1985). Nor is a covered employee free to decline his employer's request to submit to breath or urine tests under the conditions set forth in Subpart D. See § 219.11(b). An employee who refuses to submit to the tests must be withdrawn from covered service. See 4 App. to Field Manual 18.
In light of these provisions, we are unwilling to accept petitioners' submission that tests conducted by private railroads in reliance on Subpart D will be primarily the result of private initiative. The Government has removed all legal barriers to the testing authorized by Subpart D, and indeed has made plain not only its strong preference for testing, but also its desire to share the fruits of such intrusions. In addition, it has mandated that the railroads not bargain away the authority to perform tests granted by Subpart D. These are clear indices of the Government's encouragement, endorsement, *616 and participation, and suffice to implicate the Fourth Amendment.
B
Our precedents teach that where, as here, the Government seeks to obtain physical evidence from a person, the Fourth Amendment may be relevant at several levels. See, e. g., United States v. Dionisio, 410 U. S. 1, 8 (1973). The initial detention necessary to procure the evidence may be a seizure of the person, Cupp v. Murphy, 412 U. S. 291, 294-295 (1973); Davis v. Mississippi, 394 U. S. 721, 726-727 (1969), if the detention amounts to a meaningful interference with his freedom of movement. INS v. Delgado, 466 U. S. 210, 215 (1984); United States v. Jacobsen, supra, at 113, n. 5. Obtaining and examining the evidence may also be a search, see Cupp v. Murphy, supra, at 295; United States v. Dionisio, supra, at 8, 13-14, if doing so infringes an expectation of privacy that society is prepared to recognize as reasonable, see, e. g., California v. Greenwood, 486 U. S. 35, 43 (1988); United States v. Jacobsen, supra, at 113.
We have long recognized that a "compelled intrusio[n] into the body for blood to be analyzed for alcohol content" must be deemed a Fourth Amendment search. See Schmerber v. California, 384 U. S. 757, 767-768 (1966). See also Winston v. Lee, 470 U. S. 753, 760 (1985). In light of our society's concern for the security of one's person, see, e. g., Terry v. Ohio, 392 U. S. 1, 9 (1968), it is obvious that this physical intrusion, penetrating beneath the skin, infringes an expectation of privacy that society is prepared to recognize as reasonable. The ensuing chemical analysis of the sample to obtain physiological data is a further invasion of the tested employee's privacy interests. Cf. Arizona v. Hicks, 480 U. S. 321, 324-325 (1987). Much the same is true of the breath-testing procedures required under Subpart D of the regulations. Subjecting a person to a breathalyzer test, which generally requires the production of alveolar or "deep lung" breath for chemical analysis, see, e. g., California v. *617 Trombetta, 467 U. S. 479, 481 (1984), implicates similar concerns about bodily integrity and, like the blood-alcohol test we considered in Schmerber, should also be deemed a search, see 1 W. LaFave, Search and Seizure § 2.6(a), p. 463 (1987). See also Burnett v. Anchorage, 806 F. 2d 1447, 1449 (CA9 1986); Shoemaker v. Handel, 795 F. 2d 1136, 1141 (CA3), cert. denied, 479 U. S. 986 (1986).
Unlike the blood-testing procedure at issue in Schmerber, the procedures prescribed by the FRA regulations for collecting and testing urine samples do not entail a surgical intrusion into the body. It is not disputed, however, that chemical analysis of urine, like that of blood, can reveal a host of private medical facts about an employee, including whether he or she is epileptic, pregnant, or diabetic. Nor can it be disputed that the process of collecting the sample to be tested, which may in some cases involve visual or aural monitoring of the act of urination, itself implicates privacy interests. As the Court of Appeals for the Fifth Circuit has stated:
"There are few activities in our society more personal or private than the passing of urine. Most people describe it by euphemisms if they talk about it at all. It is a function traditionally performed without public observation; indeed, its performance in public is generally prohibited by law as well as social custom." National Treasury Employees Union v. Von Raab, 816 F. 2d 170, 175 (1987).
Because it is clear that the collection and testing of urine intrudes upon expectations of privacy that society has long recognized as reasonable, the Federal Courts of Appeals have concluded unanimously, and we agree, that these intrusions must be deemed searches under the Fourth Amendment.[4]
*618 In view of our conclusion that the collection and subsequent analysis of the requisite biological samples must be deemed Fourth Amendment searches, we need not characterize the employer's antecedent interference with the employee's freedom of movement as an independent Fourth Amendment seizure. As our precedents indicate, not every governmental interference with an individual's freedom of movement raises such constitutional concerns that there is a seizure of the person. See United States v. Dionisio, supra, at 9-11 (grand jury subpoena, though enforceable by contempt, does not effect a seizure of the person); United States v. Mara, 410 U. S. 19, 21 (1973) (same). For present purposes, it suffices to note that any limitation on an employee's freedom of movement that is necessary to obtain the blood, urine, or breath samples contemplated by the regulations must be considered in assessing the intrusiveness of the searches effected by the Government's testing program. Cf. United States v. Place, 462 U. S. 696, 707-709 (1983).
III
A
To hold that the Fourth Amendment is applicable to the drug and alcohol testing prescribed by the FRA regulations *619 is only to begin the inquiry into the standards governing such intrusions. O'Connor v. Ortega, 480 U. S. 709, 719 (1987) (plurality opinion); New Jersey v. T. L. O., 469 U. S. 325, 337 (1985). For the Fourth Amendment does not proscribe all searches and seizures, but only those that are unreasonable. United States v. Sharpe, 470 U. S. 675, 682 (1985); Schmerber v. California, 384 U. S., at 768. What is reasonable, of course, "depends on all of the circumstances surrounding the search or seizure and the nature of the search or seizure itself." United States v. Montoya de Hernandez, 473 U. S. 531, 537 (1985). Thus, the permissibility of a particular practice "is judged by balancing its intrusion on the individual's Fourth Amendment interests against its promotion of legitimate governmental interests." Delaware v. Prouse, 440 U. S., at 654; United States v. Martinez-Fuerte, 428 U. S. 543 (1976).
In most criminal cases, we strike this balance in favor of the procedures described by the Warrant Clause of the Fourth Amendment. See United States v. Place, supra, at 701, and n. 2; United States v. United States District Court, 407 U. S. 297, 315 (1972). Except in certain well-defined circumstances, a search or seizure in such a case is not reasonable unless it is accomplished pursuant to a judicial warrant issued upon probable cause. See, e. g., Payton v. New York, 445 U. S. 573, 586 (1980); Mincey v. Arizona, 437 U. S. 385, 390 (1978). We have recognized exceptions to this rule, however, "when `special needs, beyond the normal need for law enforcement, make the warrant and probable-cause requirement impracticable.' " Griffin v. Wisconsin, 483 U. S. 868, 873 (1987), quoting New Jersey v. T. L. O., supra, at 351 (BLACKMUN, J., concurring in judgment). When faced with such special needs, we have not hesitated to balance the governmental and privacy interests to assess the practicality of the warrant and probable-cause requirements in the particular context. See, e. g., Griffin v. Wisconsin, supra, at 873 (search of probationer's home); New York v. *620 Burger, 482 U. S. 691, 699-703 (1987) (search of premises of certain highly regulated businesses); O'Connor v. Ortega, supra, at 721-725 (work-related searches of employees' desks and offices); New Jersey v. T. L. O., supra, at 337-342 (search of student's property by school officials); Bell v. Wolfish, 441 U. S. 520, 558-560 (1979) (body cavity searches of prison inmates).
The Government's interest in regulating the conduct of railroad employees to ensure safety, like its supervision of probationers or regulated industries, or its operation of a government office, school, or prison, "likewise presents `special needs' beyond normal law enforcement that may justify departures from the usual warrant and probable-cause requirements." Griffin v. Wisconsin, supra, at 873-874. The hours of service employees covered by the FRA regulations include persons engaged in handling orders concerning train movements, operating crews, and those engaged in the maintenance and repair of signal systems. 50 Fed. Reg. 31511 (1985). It is undisputed that these and other covered employees are engaged in safety-sensitive tasks. The FRA so found, and respondents conceded the point at oral argument. Tr. of Oral Arg. 46-47. As we have recognized, the whole premise of the Hours of Service Act is that "[t]he length of hours of service has direct relation to the efficiency of the human agencies upon which protection [of] life and property necessarily depends." Baltimore & Ohio R. Co. v. ICC, 221 U. S. 612, 619 (1911). See also Atchison, T. & S. F. R. Co. v. United States, 244 U. S. 336, 342 (1917) ("[I]t must be remembered that the purpose of the act was to prevent the dangers which must necessarily arise to the employee and to the public from continuing men in a dangerous and hazardous business for periods so long as to render them unfit to give that service which is essential to the protection of themselves and those entrusted to their care").
The FRA has prescribed toxicological tests, not to assist in the prosecution of employees, but rather "to prevent accidents *621 and casualties in railroad operations that result from impairment of employees by alcohol or drugs." 49 CFR § 219.1(a) (1987).[5] This governmental interest in ensuring the safety of the traveling public and of the employees themselves plainly justifies prohibiting covered employees from using alcohol or drugs on duty, or while subject to being called for duty. This interest also "require[s] and justif[ies] the exercise of supervision to assure that the restrictions are in fact observed." Griffin v. Wisconsin, supra, at 875. The question that remains, then, is whether the Government's need to monitor compliance with these restrictions justifies the privacy intrusions at issue absent a warrant or individualized suspicion.
B
An essential purpose of a warrant requirement is to protect privacy interests by assuring citizens subject to a search *622 or seizure that such intrusions are not the random or arbitrary acts of government agents. A warrant assures the citizen that the intrusion is authorized by law, and that it is narrowly limited in its objectives and scope. See, e. g., New York v. Burger, supra, at 703; United States v. Chadwick, 433 U. S. 1, 9 (1977); Camara v. Municipal Court of San Francisco, 387 U. S., at 532. A warrant also provides the detached scrutiny of a neutral magistrate, and thus ensures an objective determination whether an intrusion is justified in any given case. See United States v. Chadwick, supra, at 9. In the present context, however, a warrant would do little to further these aims. Both the circumstances justifying toxicological testing and the permissible limits of such intrusions are defined narrowly and specifically in the regulations that authorize them, and doubtless are well known to covered employees. Cf. United States v. Biswell, 406 U. S. 311, 316 (1972). Indeed, in light of the standardized nature of the tests and the minimal discretion vested in those charged with administering the program, there are virtually no facts for a neutral magistrate to evaluate. Cf. Colorado v. Bertine, 479 U. S. 367, 376 (1987) (BLACKMUN, J., concurring).[6]
*623 We have recognized, moreover, that the government's interest in dispensing with the warrant requirement is at its strongest when, as here, "the burden of obtaining a warrant is likely to frustrate the governmental purpose behind the search." Camara v. Municipal Court of San Francisco, supra, at 533. See also New Jersey v. T. L. O., 469 U. S., at 340; Donovan v. Dewey, 452 U. S. 594, 603 (1981). As the FRA recognized, alcohol and other drugs are eliminated from the bloodstream at a constant rate, see 49 Fed. Reg. 24291 (1984), and blood and breath samples taken to measure whether these substances were in the bloodstream when a triggering event occurred must be obtained as soon as possible. See Schmerber v. California, 384 U. S., at 770-771. Although the metabolites of some drugs remain in the urine for longer periods of time and may enable the FRA to estimate whether the employee was impaired by those drugs at the time of a covered accident, incident, or rule violation, 49 Fed. Reg. 24291 (1984), the delay necessary to procure a warrant nevertheless may result in the destruction of valuable evidence.
The Government's need to rely on private railroads to set the testing process in motion also indicates that insistence on a warrant requirement would impede the achievement of the Government's objective. Railroad supervisors, like school officials, see New Jersey v. T. L. O., supra, at 339-340, and hospital administrators, see O'Connor v. Ortega, 480 U. S., at 722, are not in the business of investigating violations of the criminal laws or enforcing administrative codes, and otherwise have little occasion to become familiar with the intricacies of this Court's Fourth Amendment jurisprudence. "Imposing unwieldy warrant procedures . . . upon supervisors, *624 who would otherwise have no reason to be familiar with such procedures, is simply unreasonable." Ibid.
In sum, imposing a warrant requirement in the present context would add little to the assurances of certainty and regularity already afforded by the regulations, while significantly hindering, and in many cases frustrating, the objectives of the Government's testing program. We do not believe that a warrant is essential to render the intrusions here at issue reasonable under the Fourth Amendment.
C
Our cases indicate that even a search that may be performed without a warrant must be based, as a general matter, on probable cause to believe that the person to be searched has violated the law. See New Jersey v. T. L. O., supra, at 340. When the balance of interests precludes insistence on a showing of probable cause, we have usually required "some quantum of individualized suspicion" before concluding that a search is reasonable. See, e. g., United States v. Martinez-Fuerte, 428 U. S., at 560. We made it clear, however, that a showing of individualized suspicion is not a constitutional floor, below which a search must be presumed unreasonable. Id., at 561. In limited circumstances, where the privacy interests implicated by the search are minimal, and where a