511 U.S. 825 (1994)

FARMER
v.
BRENNAN, WARDEN, et al.

No. 92-7247.

United States Supreme Court.

Argued January 12, 1994. Decided June 6, 1994. CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE SEVENTH CIRCUIT

*826 *827 Souter, J., delivered the opinion of the Court, in which Rehnquist, C. J., and Blackmun, Stevens, O'Connor, Scalia, Kennedy, and Ginsburg, JJ., joined. Blackmun, J., post, p. 851, and Stevens, J., post, p. 858, filed concurring opinions. Thomas, J., filed an opinion concurring in the judgment, post, p. 858.

Elizabeth Alexander argued the cause for petitioner. With her on the briefs were Alvin J. Bronstein, by appointment of the Court, 510 U. S. 941, and Steven R. Shapiro.

Deputy Solicitor General Bender argued the cause for respondents. With him on the brief were Solicitor General *828 Days, Assistant Attorney General Hunger, Amy L. Wax, Barbara L. Herwig, and Robert M. Loeb.^[*]

Justice Souter, delivered the opinion of the Court.

A prison official's "deliberate indifference" to a substantial risk of serious harm to an inmate violates the Eighth Amendment. See Helling v. McKinney 509 U. S. 25 (1993); Wilson v. Seiter, 501 U. S. 294 (1991); Estelle v. Gamble, 429 *829 U. S. 97 (1976). This case requires us to define the term "deliberate indifference," as we do by requiring a showing that the official was subjectively aware of the risk.

I

The dispute before us stems from a civil suit brought by petitioner, Dee Farmer, alleging that respondents, federal prison officials, violated the Eighth Amendment by their deliberate indifference to petitioner's safety. Petitioner, who is serving a federal sentence for credit card fraud, has been diagnosed by medical personnel of the Bureau of Prisons as a transsexual, one who has "[a] rare psychiatric disorder in which a person feels persistently uncomfortable about his or her anatomical sex," and who typically seeks medical treatment, including hormonal therapy and surgery, to bring about a permanent sex change. American Medical Association, Encyclopedia of Medicine 1006 (1989); see also American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders 74-75 (3d rev. ed. 1987). For several years before being convicted and sentenced in 1986 at the age of 18, petitioner, who is biologically male, wore women's clothing (as petitioner did at the 1986 trial), underwent estrogen therapy, received silicone breast implants, and submitted to unsuccessful "black market" testicle-removal surgery. See Farmer v. Haas, 990 F. 2d 319, 320 (CA7 1993). Petitioner's precise appearance in prison is unclear from the record before us, but petitioner claims to have continued hormonal treatment while incarcerated by using drugs smuggled into prison, and apparently wears clothing in a feminine manner, as by displaying a shirt "off one shoulder," App. 112. The parties agree that petitioner "projects feminine characteristics." Id. , at 51, 74.

The practice of federal prison authorities is to incarcerate preoperative transsexuals with prisoners of like biological sex, see Farmer v. Haas, supra, at 320, and over time authorities housed petitioner in several federal facilities, sometimes *830 in the general male prison population but more often in segregation. While there is no dispute that petitioner was segregated at least several times because of violations of prison rules, neither is it disputed that in at least one penitentiary petitioner was segregated because of safety concerns. See Farmer v. Carlson, 685 F. Supp. 1335, 1342 (MD Pa. 1988).

On March 9, 1989, petitioner was transferred for disciplinary reasons from the Federal Correctional Institute in Oxford, Wisconsin (FCI-Oxford), to the United States Penitentiary in Terre Haute, Indiana (USP-Terre Haute). Though the record before us is unclear about the security designations of the two prisons in 1989, penitentiaries are typically higher security facilities that house more troublesome prisoners than federal correctional institutes. See generally Federal Bureau of Prisons, Facilities 1990. After an initial stay in administrative segregation, petitioner was placed in the USP-Terre Haute general population. Petitioner voiced no objection to any prison official about the transfer to the penitentiary or to placement in its general population. Within two weeks, according to petitioner's allegations, petitioner was beaten and raped by another inmate in petitioner's cell. Several days later, after petitioner claims to have reported the incident, officials returned petitioner to segregation to await, according to respondents, a hearing about petitioner's HIV-positive status.

Acting without counsel, petitioner then filed a Bivens complaint, alleging a violation of the Eighth Amendment. See Bivens v. Six Unknown Fed. Narcotics Agents, 403 U. S. 388 (1971); Carlson v. Green, 446 U. S. 14 (1980). As defendants, petitioner named respondents: the warden of USP-Terre Haute and the Director of the Bureau of Prisons (sued only in their official capacities); the warden of FCI-Oxford and a case manager there; and the Director of the Bureau of Prisons North Central Region Office and an official in that office (sued in their official and personal capacities). As later amended, the complaint alleged that respondents either *831 transferred petitioner to USP-Terre Haute or placed petitioner in its general population despite knowledge that the penitentiary had a violent environment and a history of inmate assaults, and despite knowledge that petitioner, as a transsexual who "projects feminine characteristics," would be particularly vulnerable to sexual attack by some USPTerre Haute inmates. This allegedly amounted to a deliberately indifferent failure to protect petitioner's safety, and thus to a violation of petitioner's Eighth Amendment rights. Petitioner sought compensatory and punitive damages, and an injunction barring future confinement in any penitentiary, including USP-Terre Haute.^[1]

Respondents filed a motion for summary judgment supported by several affidavits, to which petitioner responded with an opposing affidavit and a cross-motion for summary judgment; petitioner also invoked Federal Rule of Civil Procedure 56(f), asking the court to delay its ruling until respondents had complied with petitioner's pending request for production of documents. Respondents then moved for a protective order staying discovery until resolution of the issue of qualified immunity, raised in respondents' summary judgment motion.

Without ruling on respondents' request to stay discovery, the District Court denied petitioner's Rule 56(f) motion and granted summary judgment to respondents, concluding that there had been no deliberate indifference to petitioner's safety. The failure of prison officials to prevent inmate assaults violates the Eighth Amendment, the court stated, only if prison officials were "reckless in a criminal sense," meaning that they had "actual knowledge" of a potential danger. App. 124. Respondents, however, lacked the requisite *832 knowledge, the court found. "[Petitioner] never expressed any concern for his safety to any of [respondents]. Since [respondents] had no knowledge of any potential danger to [petitioner], they were not deliberately indifferent to his safety." Ibid.

The United States Court of Appeals for the Seventh Circuit summarily affirmed without opinion. We granted certiorari, 510 U. S. 811 (1993), because Courts of Appeals had adopted inconsistent tests for "deliberate indifference." Compare, for example, McGill v. Duckworth, 944 F. 2d 344, 348 (CA7 1991) (holding that "deliberate indifference" requires a "subjective standard of recklessness"), cert. denied, 503 U. S. 907 (1992), with Young v. Quinlan, 960 F. 2d 351, 360-361 (CA3 1992) ("[A] prison official is deliberately indifferent when he knows or should have known of a sufficiently serious danger to an inmate").

II

A

The Constitution "does not mandate comfortable prisons," Rhodes v. Chapman, 452 U. S. 337, 349 (1981), but neither does it permit inhumane ones, and it is now settled that "the treatment a prisoner receives in prison and the conditions under which he is confined are subject to scrutiny under the Eighth Amendment," Helling, 509 U. S., at 31. In its prohibition of "cruel and unusual punishments," the Eighth Amendment places restraints on prison officials, who may not, for example, use excessive physical force against prisoners. See Hudson v. McMillian, 503 U. S. 1 (1992). The Amendment also imposes duties on these officials, who must provide humane conditions of confinement; prison officials must ensure that inmates receive adequate food, clothing, shelter, and medical care, and must "take reasonable measures to guarantee the safety of the inmates," Hudson v. Palmer, 468 U. S. 517, 526-527 (1984). See Helling, supra, *833 at 31-32; Washington v. Harper, 494 U. S. 210, 225 (1990); Estelle, 429 U. S., at 103. Cf. DeShaney v. Winnebago County Dept. of Social Servs., 489 U. S. 189, 198-199 (1989).

In particular, as the lower courts have uniformly held, and as we have assumed, "prison officials have a duty . . . to protect prisoners from violence at the hands of other prisoners." Cortes-Quinones v. Jimenez-Nettleship, 842 F. 2d 556, 558 (CA1) (internal quotation marks and citation omitted), cert. denied, 488 U. S. 823 (1988);^[2] see also Wilson v. Seiter, 501 U. S., at 303 (describing "the protection [an inmate] is afforded against other inmates" as a "conditio[n] of confinement" subject to the strictures of the Eighth Amendment). Having incarcerated "persons [with] demonstrated proclivit[ies] for antisocial criminal, and often violent, conduct," Hudson v. Palmer, supra, at 526, having stripped them of virtually every means of self-protection and foreclosed their access to outside aid, the government and its officials are not free to let the state of nature take its course. Cf. DeShaney, supra, at 199-200; Estelle , supra, at 103-104. Prison conditions may be "restrictive and even harsh," Rhodes, supra, at 347, but gratuitously allowing the beating or rape of one prisoner by another serves no "legitimate penological objectiv[e]," Hudson v. Palmer, supra, at 548 (Stevens, J., concurring in part and dissenting in part), any more than it squares with "`evolving standards of decency,' " Estelle , *834 supra, at 102 (quoting Trop v. Dulles, 356 U. S. 86, 101 (1958) (plurality opinion)). Being violently assaulted in prison is simply not "part of the penalty that criminal offenders pay for their offenses against society." Rhodes , supra, at 347.

It is not, however, every injury suffered by one prisoner at the hands of another that translates into constitutional liability for prison officials responsible for the victim's safety. Our cases have held that a prison official violates the Eighth Amendment only when two requirements are met. First, the deprivation alleged must be, objectively, "sufficiently serious," Wilson, supra, at 298; see also Hudson v. McMillian, supra, at 5; a prison official's act or omission must result in the denial of "the minimal civilized measure of life's necessities," Rhodes, supra, at 347. For a claim (like the one here) based on a failure to prevent harm, the inmate must show that he is incarcerated under conditions posing a substantial risk of serious harm. See Helling, supra, at 35.^[3]

The second requirement follows from the principle that "only the unnecessary and wanton infliction of pain implicates the Eighth Amendment." Wilson, 501 U. S., at 297 (internal quotation marks, emphasis, and citations omitted). To violate the Cruel and Unusual Punishments Clause, a prison official must have a "sufficiently culpable state of mind." Ibid.; see also id. , at 302-303; Hudson v. McMillian, supra, at 8. In prison-conditions cases that state of mind is one of "deliberate indifference" to inmate health or safety, Wilson, supra, at 302-303; see also Helling, supra, at 34-35; Hudson v. McMillian, supra, at 5; Estelle, supra, at 106, a standard the parties agree governs the claim in this case. The parties disagree, however, on the proper test for deliberate indifference, which we must therefore undertake to define.

*835 B

1

Although we have never paused to explain the meaning of the term "deliberate indifference," the case law is instructive. The term first appeared in the United States Reports in Estelle v. Gamble, 429 U. S., at 104, and its use there shows that deliberate indifference describes a state of mind more blameworthy than negligence. In considering the inmate's claim in Estelle that inadequate prison medical care violated the Cruel and Unusual Punishments Clause, we distinguished "deliberate indifference to serious medical needs of prisoners," ibid. , from "negligen[ce] in diagnosing or treating a medical condition," id. , at 106, holding that only the former violates the Clause. We have since read Estelle for the proposition that Eighth Amendment liability requires "more than ordinary lack of due care for the prisoner's interests or safety." Whitley v. Albers, 475 U. S. 312, 319 (1986).

While Estelle establishes that deliberate indifference entails something more than mere negligence, the cases are also clear that itis satisfied by something less than acts or omissions for the very purpose of causing harm or with knowledge that harm will result. That point underlies the ruling that "application of the deliberate indifference standard is inappropriate" in one class of prison cases: when "officials stand accused of using excessive physical force." Hudson v. McMillian, 503 U. S., at 6-7; see also Whitley, supra, at 320. In such situations, where the decisions of prison officials are typically made "`in haste, under pressure, and frequently without the luxury of a second chance,' " Hudson v. McMillian, supra, at 6 (quoting Whitley, supra, at 320), an Eighth Amendment claimant must show more than "indifference," deliberate or otherwise. The claimant must show that officials applied force "maliciously and sadistically for the very purpose of causing harm," 503 U. S., at 6 (internal quotation marks and citations omitted), or, as the Court also *836 put it, that officials used force with "a knowing willingness that [harm] occur," id., at 7 (internal quotation marks and citation omitted). This standard of purposeful or knowing conduct is not, however, necessary to satisfy the mens rea requirement of deliberate indifference for claims challenging conditions of confinement; "the very high state of mind prescribed by Whitley does not apply to prison conditions cases." Wilson, supra, at 302-303.

With deliberate indifference lying somewhere between the poles of negligence at one end and purpose or knowledge at the other, the Courts of Appeals have routinely equated deliberate indifference with recklessness.^[4] See, e. g., LaMarca v. Turner, 995 F. 2d 1526, 1535 (CA11 1993); Manarite v. Springfield, 957 F. 2d 953, 957 (CA1 1992); Redman v. County of San Diego, 942 F. 2d 1435, 1443 (CA9 1991); McGill v. Duckworth, 944 F. 2d, at 347; Miltier v. Beorn, 896 F. 2d 848, 851-852 (CA4 1990); Martin v. White, 742 F. 2d 469, 474 (CA8 1984); see also Springfield v. Kibbe, 480 U. S. 257, 269 (1987) (O'Connor, J., dissenting). It is, indeed, fair to say that acting or failing to act with deliberate indifference to a substantial risk of serious harm to a prisoner is the equivalent of recklessly disregarding that risk.

That does not, however, fully answer the pending question about the level of culpability deliberate indifference entails, for the term recklessness is not self-defining. The civil law generally calls a person reckless who acts or (if the person has a duty to act) failsto act in the face of an unjustifiably high risk of harm that is either known or so obvious that it should be known. See Prosser and Keeton § 34, pp. 213-214; Restatement (Second) of Torts § 500 (1965). The criminal *837 law, however, generally permits a finding of recklessness only when a person disregards a risk of harm of which he is aware. See R. Perkins & R. Boyce, Criminal Law 850-851 (3d ed. 1982); J. Hall, General Principles of Criminal Law 115-116, 120, 128 (2d ed. 1960) (hereinafter Hall); American Law Institute, Model Penal Code § 2.02(2)(c), and Comment 3 (1985); but see Commonwealth v. Pierce, 138 Mass. 165, 175-178 (1884) (Holmes, J.) (adopting an objective approach to criminal recklessness). The standards proposed by the parties in this case track the two approaches (though the parties do not put it that way): petitioner asks us to define deliberate indifference as what we have called civil-law recklessness,^[5] and respondents urge us to adopt an approach consistent with recklessness in the criminal law.^[6]

We reject petitioner's invitation to adopt an objective test for deliberate indifference. We hold instead that a prison official cannot be found liable under the Eighth Amendment for denying an inmate humane conditions of confinement unless the official knows of and disregards an excessive risk to inmate health or safety; the official must both be aware of facts from which the inference could be drawn that a substantial risk of serious harm exists, and he must also draw the inference. This approach comports best with the text of the Amendment as our cases have interpreted it. The Eighth Amendment does not outlaw cruel and unusual "conditions"; it outlaws cruel and unusual "punishments." An act or omission unaccompanied by knowledge of a significant risk of harm might well be something society wishes to discourage, *838 and if harm does result society might well wish to assure compensation. The common law reflects such concerns when it imposes tort liability on a purely objective basis. See Prosser and Keeton §§ 2, 34, pp. 6, 213-214; see also Federal Tort Claims Act, 28 U. S. C. §§ 2671-2680; United States v. Muniz, 374 U. S. 150 (1963). But an official's failure to alleviate a significant risk that he should have perceived but did not, while no cause for commendation, cannot under our cases be condemned as the infliction of punishment.

In Wilson v. Seiter, we rejected a reading of the Eighth Amendment that would allow liability to be imposed on prison officials solely because of the presence of objectively inhumane prison conditions. See 501 U. S., at 299-302. As we explained there, our "cases mandate inquiry into a prison official's state of mind when it is claimed that the official has inflicted cruel and unusual punishment." Id. , at 299. Although "state of mind," like "intent," is an ambiguous term that can encompass objectively defined levels of blameworthiness, see 1 W. LaFave & A. Scott, Substantive Criminal Law §§ 3.4, 3.5, pp. 296-300, 313-314 (1986) (hereinafter LaFave & Scott); United States v. Bailey, 444 U. S. 394, 404 (1980), it was no accident that we said in Wilson and repeated in later cases that Eighth Amendment suits against prison officials must satisfy a "subjective" requirement. See Wilson, supra, at 298; see also Helling, 509 U. S., at 35; Hudson v. McMillian, 503 U. S., at 8. It is true, as petitioner points out, that Wilson cited with approval Court of Appeals decisions applying an objective test for deliberate indifference to claims based on prison officials' failure to prevent inmate assaults. See 501 U. S., at 303 (citing CortesQuinones v. Jimenez-Nettleship, 842 F. 2d, at 560; and Morgan v. District of Columbia, 824 F. 2d 1049, 1057-1058 (CADC 1987)). But Wilson cited those cases for the proposition that the deliberate indifference standard applies to all prison-conditions claims, not to undo its holding that the *839 Eighth Amendment has a "subjective component." 501 U. S., at 298. Petitioner's purely objective test for deliberate indifference is simply incompatible with Wilson `s holding.

To be sure, the reasons for focusing on what a defendant's mental attitude actually was (or is), rather than what it should have been (or should be), differ in the Eighth Amendment context from that of the criminal law. Here, a subjective approach isolates those who inflict punishment; there, it isolates those against whom punishment should be inflicted. But the result is the same: to act recklessly in either setting a person must "consciously disregar[d]" a substantial risk of serious harm. Model Penal Code § 2.02(2)(c).

At oral argument, the Deputy Solicitor General advised against frank adoption of a criminal-law mens rea requirement, contending that it could encourage triers of fact to find Eighth Amendment liability only if they concluded that prison officials acted like criminals. See Tr. of Oral Arg. 39— 40. We think this concern is misdirected. Bivens actions against federal prison officials (and their 42 U. S. C. § 1983 counterparts against state officials) are civil in character, and a court should no more allude to the criminal law when enforcing the Cruel and Unusual Punishments Clause than when applying the Free Speech and Press Clauses, where we have also adopted a subjective approach to recklessness. See Harte-Hanks Communications, Inc. v. Connaughton, 491 U. S. 657, 688 (1989) (holding that the standard for "reckless disregard" for the truth in a defamation action by a public figure "is a subjective one," requiring that "the defendant in fact entertained serious doubts as to the truth of his publication," or that "the defendant actually had a high degree of awareness of . . . probable falsity") (internal quotation marks and citations omitted).^[7] That said, subjective recklessness as used in the criminal law is a familiar and workable standard *840 that is consistent with the Cruel and Unusual Punishments Clause as interpreted in our cases, and we adopt it as the test for "deliberate indifference" under the Eighth Amendment.

2

Our decision that Eighth Amendment liability requires consciousness of a risk is thus based on the Constitution and our cases, not merely on a parsing of the phrase "deliberate indifference." And we do not reject petitioner's arguments for a thoroughly objective approach to deliberate indifference without recognizing that on the crucial point (whether a prison official must know of a risk, or whether it suffices that he should know) the term does not speak with certainty. Use of "deliberate," for example, arguably requires nothing more than an act (or omission) of indifference to a serious risk that is voluntary, not accidental. Cf. Estelle, 429 U. S., at 105 (distinguishing "deliberate indifference" from "accident" or "inadverten[ce]"). And even if "deliberate" is better read as implying knowledge of a risk, the concept of constructive knowledge is familiar enough that the term "deliberate indifference" would not, of its own force, preclude a scheme that conclusively presumed awareness from a risk's obviousness.

Because "deliberate indifference" is a judicial gloss, appearing neither in the Constitution nor in a statute, we could not accept petitioner's argument that the test for "deliberate indifference" described in Canton v. Harris, 489 U. S. 378 (1989), must necessarily govern here. In Canton, interpreting Rev. Stat. § 1979, 42 U. S. C. § 1983, we held that a municipality can be liable for failure to train its employees when the municipality's failure shows "a deliberate indifference to the rights of its inhabitants." 489 U. S., at 389 (internal quotation marks omitted). In speaking to the meaning of the term, we said that "it may happen that in light of the duties assigned to specific officers or employees the need for *841 more or different training is so obvious, and the inadequacy so likely to result in the violation of constitutional rights, that the policymakers of the city can reasonably be said to have been deliberately indifferent to the need." Id. , at 390; see also id. , at 390, n. 10 (elaborating). Justice O'Connor's separate opinion for three Justices agreed with the Court's "obvious[ness]" test and observed that liability is appropriate when policymakers are "on actual or constructive notice" of the need to train, id. , at 396 (opinion concurring in part and dissenting in part). It would be hard to describe the Canton understanding of deliberate indifference, permitting liability to be premised on obviousness or constructive notice, as anything but objective.

Canton `s objective standard, however, is not an appropriate test for determining the liability of prison officials under the Eighth Amendment as interpreted in our cases. Section 1983, which merely provides a cause of action, "contains no state-of-mind requirement independent of that necessary to state a violation of the underlying constitutional right." Daniels v. Williams, 474 U. S. 327, 330 (1986). And while deliberate indifference serves under the Eighth Amendment to ensure that only inflictions of punishment carry liability, see Wilson, 501 U. S., at 299-300, the "term was used in the Canton case for the quite different purpose of identifying the threshold for holding a city responsible for the constitutional torts committed by its inadequately trained agents," Collins v. Harker Heights, 503 U. S. 115, 124 (1992), a purpose the Canton Court found satisfied by a test permitting liability when a municipality disregards "obvious" needs. Needless to say, moreover, considerable conceptual difficulty would attend any search for the subjective state of mind of a governmental entity, as distinct from that of a governmental official. For these reasons, we cannot accept petitioner's argument that Canton compels the conclusion *842 here that a prison official who was unaware of a substantial risk of harm to an inmate may nevertheless be held liable under the Eighth Amendment if the risk was obvious and a reasonable prison official would have noticed it.

We are no more persuaded by petitioner's argument that, without an objective test for deliberate indifference, prison officials will be free to ignore obvious dangers to inmates. Under the test we adopt today, an Eighth Amendment claimant need not show that a prison official acted or failed to act believing that harm actually would befall an inmate; it is enough that the official acted or failed to act despite his knowledge of a substantial risk of serious harm. Cf. 1 C. Torcia, Wharton's Criminal Law § 27, p. 141 (14th ed. 1978); Hall 115. We doubt that a subjective approach will present prison officials with any serious motivation "to take refuge in the zone between `ignorance of obvious risks' and `actual knowledge of risks.' " Brief for Petitioner 27. Whether a prison official had the requisite knowledge of a substantial risk is a question of fact subject to demonstration in the usual ways, including inference from circumstantial evidence, cf. Hall 118 (cautioning against "confusing a mental state with the proof of its existence"), and a factfinder may conclude that a prison official knew of a substantial risk from the very fact that the risk was obvious. Cf. LaFave & Scott § 3.7, p. 335 ("[I]f the risk is obvious, so that a reasonable man would realize it, we might well infer that [the defendant] did in fact realize it; but the inference cannot be conclusive, for we know that people are not always conscious of what reasonable people would be conscious of"). For example, if an Eighth Amendment plaintiff presents evidence showing that a substantial risk of inmate attacks was "longstanding, pervasive, well-documented, or expressly noted by prison officials in the past, and the circumstances suggest that the defendant-official being sued had been exposed to information concerning the risk and thus `must have known' about it, then such evidence could be sufficient to permit a trier of *843 fact to find that the defendant-official had actual knowledge of the risk." Brief for Respondents 22.^[8]

Nor may a prison official escape liability for deliberate indifference by showing that, while he was aware of an obvious, substantial risk to inmate safety, he did not know that the complainant was especially likely to be assaulted by the specific prisoner who eventually committed the assault. The question under the Eighth Amendment is whether prison officials, acting with deliberate indifference, exposed a prisoner to a sufficiently substantial "risk of serious damage to his future health," Helling, 509 U. S., at 35, and it does not matter whether the risk comes from a single source or multiple sources, any more than it matters whether a prisoner faces an excessive risk of attack for reasons personal to him or because all prisoners in his situation face such a risk. See Brief for Respondents 15 (stating that a prisoner can establish exposure to a sufficiently serious risk of harm "by showing that he belongs to an identifiable group of prisoners who are frequently singled out for violent attack by other inmates"). If, for example, prison officials were aware that inmate "rape was so common and uncontrolled that some potential victims dared not sleep [but] instead . . . would leave *844 their beds and spend the night clinging to the bars nearest the guards' station," Hutto v. Finney, 437 U. S. 678, 681-682, n. 3 (1978), it would obviously be irrelevant to liability that the officials could not guess beforehand precisely who would attack whom. Cf. Helling, supra, at 33 (observing that the Eighth Amendment requires a remedy for exposure of inmates to "infectious maladies" such as hepatitis and venereal disease "even though the possible infection might not affect all of those exposed"); Commonwealth v. Welansky, 316 Mass. 383, 55 N. E. 2d 902 (1944) (affirming conviction for manslaughter under a law requiring reckless or wanton conduct of a nightclub owner who failed to protect patrons from a fire, even though the owner did not know in advance who would light the match that ignited the fire or which patrons would lose their lives); State v. Julius, 185 W. Va. 422, 431— 432, 408 S. E. 2d 1, 10-11 (1991) (holding that a defendant may be held criminally liable for injury to an unanticipated victim).

Because, however, prison officials who lacked knowledge of a risk cannot be said to have inflicted punishment, it remains open to the officials to prove that they were unaware even of an obvious risk to inmate health or safety. That a trier of fact may infer knowledge from the obvious, in other words, does not mean that it must do so. Prison officials charged with deliberate indifference might show, for example, that they did not know of the underlying facts indicating a sufficiently substantial danger and that they were therefore unaware of a danger, or that they knew the underlying facts but believed (albeit unsoundly) that the risk to which the facts gave rise was insubstantial or nonexistent.

In addition, prison officials who actually knew of a substantial risk to inmate health or safety may be found free from liability if they responded reasonably to the risk, even if the harm ultimately was not averted. A prison official's duty under the Eighth Amendment is to ensure "`reasonable safety,' " Helling, supra, at 33; see also Washington v. Har- *845 per, 494 U. S., at 225; Hudson v. Palmer, 468 U. S., at 526— 527, a standard that incorporates due regard for prison officials' "unenviable task of keeping dangerous men in safe custody under humane conditions," Spain v. Procunier,