delivered the opinion of the Court.
In Stone v. Powell, 428 U. S. 465 (1976), we held that when a State has given a full and fair chance to litigate a Fourth Amendment claim, federal habeas review is not available to a state prisoner alleging that his conviction rests on evidence *683obtained through an unconstitutional search or seizure. Today we hold that Stone’s restriction on the exercise of federal habeas jurisdiction does not extend to a state prisoner’s claim that his conviction rests on statements obtained in violation of the safeguards mandated by Miranda v. Arizona, 384 U. S. 436 (1966).
I
Police officers in Romulus, Michigan, learned that respondent, Robert Allen Williams, Jr., might have information about a double murder committed on April 6, 1985. On April 10, two officers called at Williams’s house and asked him to the police station for questioning. Williams agreed to go. The officers searched Williams, but did not handcuff him, and they all drove to the station in an unmarked car. One officer, Sergeant David Early, later testified that Williams was not under arrest at this time, although a contemporaneous police report indicates that the officers arrested Williams at his residence. App. 12a-13a, 24a-26a.
At the station, the officers questioned Williams about his knowledge of the crime. Although he first denied any involvement, he soon began to implicate himself, and the officers continued their questioning, assuring Williams that their only concern was the identity of the “shooter.” After consulting each other, the officers decided not to advise Williams of his rights under Miranda v. Arizona, supra. See App. to Pet. for Cert. 48a. When Williams persisted in denying involvement, Sergeant Early reproved him:
“You know everything that went down. You just don’t want to talk about it. What it’s gonna amount to is you can talk about it now and give us the truth and we’re gonna check it out and see if it fits or else we’re simply gonna charge you and lock you up and you can just tell it to a defense attorney and let him try and prove differently.” Ibid.
*684The reproof apparently worked, for Williams then admitted he had furnished the murder weapon to the killer, who had called Williams after the crime and told him where he had discarded the weapon and other incriminating items. Williams maintained that he had not been present at the crime scene.
Only at this point, some 40 minutes after they began questioning him, did the officers advise Williams of his Miranda rights. Williams waived those rights and during subsequent questioning made several more inculpatory statements. Despite his prior denial, Williams admitted that he had driven the murderer to and from the scene of the crime, had witnessed the murders, and had helped the murderer dispose of incriminating evidence. The officers interrogated Williams again on April 11 and April 12, and, on April 12, the State formally charged him with murder.
Before trial, Williams moved to suppress his responses to the interrogations, and the trial court suppressed the statements of April 11 and April 12 as the products of improper delay in arraignment under Michigan law. See App. to Pet. for Cert. 90a-91a. The court declined to suppress the statements of April 10, however, ruling that the police had given Williams a timely warning of his Miranda rights. Id., at 90a. A bench trial led to Williams’s conviction on two counts each of first-degree murder and possession of a firearm during the commission of a felony and resulted in two concurrent life sentences. The Court of Appeals of Michigan affirmed the trial court’s ruling on the April 10 statements, People v. Williams, 171 Mich. App. 234, 429 N. W. 2d 649 (1988), and the Supreme Court of Michigan denied leave to appeal, 432 Mich. 913, 440 N. W. 2d 416 (1989). We denied the ensuing petition for writ of certiorari. Williams v. Michigan, 493 U. S. 956 (1989).
Williams then began this action pro se by petitioning for a writ of habeas corpus in the District Court, alleging a violation of his Miranda rights as the principal ground for relief. *685Petition for Writ of Habeas Corpus in No. 90CV-70256, p. 5 (ED Mich.). The District Court granted relief, finding that the police had placed Williams in custody for Miranda purposes when Sergeant Early had threatened to “lock [him] up,” and that the trial court should accordingly have excluded all statements Williams had made between that point and his receipt of the Miranda warnings. App. to Pet. for Cert. 49a-52a. The court also concluded, though neither Williams nor petitioner had addressed the issue, that Williams’s statements after receiving the Miranda warnings were involuntary under the Due Process Clause of the Fourteenth Amendment and thus likewise subject to suppression. App. to Pet. for Cert. 52a-71a. The court found that the totality of circumstances, including repeated promises of lenient treatment if he told the truth, had overborne Williams’s will.1
The Court of Appeals affirmed, 944 F. 2d 284 (CA6 1991), holding the District Court correct in determining the police had subjected Williams to custodial interrogation before giving him the requisite Miranda advice, and in finding the statements made after receiving the Miranda warnings involuntary. Id., at 289-290. The Court of Appeals summarily rejected the argument that the rule in Stone v. Powell, 428 U. S. 465 (1976), should apply to bar habeas review of Williams’s Miranda claim. 944 F. 2d, at 291. We granted certiorari to resolve the significant issue thus presented. 503 U. S. 983 (1992).2
*686I — J HH
We have made it clear that Stone’s limitation on federal habeas relief was not jurisdictional in nature,3 but rested on prudential concerns counseling against the application of the Fourth Amendment exclusionary rule on collateral review. See Stone, supra, at 494-495, n. 37; see also Kuhlmann v. Wilson, 477 U. S. 436, 447 (1986) (opinion of Powell, J.) (discussing equitable principles underlying Stone); Kimmelman v. Morrison, 477 U. S. 365, 379, n. 4 (1986); Allen v. McCurry, 449 U. S. 90, 103 (1980) (Stone concerns “the prudent exercise of federal-court jurisdiction under 28 U. S. C. § 2254”); cf. 28 U. S. C. § 2243 (court entertaining habeas petition shall “dispose of the matter as law and justice require”). We simply concluded in Stone that the costs of applying the exclusionary rule on collateral review outweighed any potential advantage to be gained by applying it there. Stone, supra, at 489-495.
We recognized that the exclusionary rule, held applicable to the States in Mapp v. Ohio, 367 U. S. 643 (1961), “is not a personal constitutional right”; it fails to redress “the injury to the privacy of the victim of the search or seizure” at issue, “for any ‘[rjeparation comes too late.’ ” Stone, supra, at 486 (quoting Linkletter v. Walker, 381 U. S. 618, 637 (1965)). The rule serves instead to deter future Fourth Amendment violations, and we reasoned that its application on collateral review would only marginally advance this interest in deterrence. Stone, 428 U. S., at 493. On the other side of the ledger, the costs of applying the exclusionary rule on habeas *687were comparatively great. We reasoned that doing so would not only exclude reliable evidence and divert attention from the central question of guilt, but would also intrude upon the public interest in “ ‘(i) the most effective utilization of limited judicial resources, (ii) the necessity of finality in criminal trials, (iii) the minimization of friction between our federal and state systems of justice, and (iv) the maintenance of the constitutional balance upon which the doctrine of federalism is founded.”’ Id., at 491, n. 31 (quoting Schneckloth v. Bustamonte, 412 U. S. 218, 259 (1973) (Powell, J., concurring)).
Over the years, we have repeatedly declined to extend the rule in Stone beyond its original bounds. In Jackson v. Virginia, 443 U. S. 307 (1979), for example, we denied a request to apply Stone to bar habeas consideration of a Fourteenth Amendment due process claim of insufficient evidence to support a state conviction. We stressed that the issue was “central to the basic question of guilt or innocence,” Jackson, 443 U. S., at 323, unlike a claim that a state court had received evidence in violation of the Fourth Amendment exclusionary rule, and we found that to review such a claim on habeas imposed no great burdens on the federal courts. Id., at 321-322.
After a like analysis, in Rose v. Mitchell, 443 U. S. 545 (1979), we decided against extending Stone to foreclose habeas review of an equal protection claim of racial discrimination in selecting a state grand-jury foreman. A charge that state adjudication had violated the direct command of the Fourteenth Amendment implicated the integrity of the judicial process, we reasoned, Rose, 443 U. S., at 563, and failed to raise the “federalism concerns” that had driven the Court in Stone. 443 U. S., at 562. Since federal courts had granted relief to state prisoners upon proof of forbidden discrimination for nearly a century, we concluded, “confirmation that habeas corpus remains an appropriate vehicle by which federal courts are to exercise their Fourteenth Amendment *688responsibilities” would not likely raise tensions between the state and federal judicial systems. Ibid.
In a third instance, in Kimmelman v. Morrison, supra, we again declined to extend Stone, in that case to bar habeas review of certain claims of ineffective assistance of counsel under the Sixth Amendment. We explained that unlike the Fourth Amendment, which confers no “trial right,” the Sixth confers a “fundamental right” on criminal defendants, one that “assures the fairness, and thus the legitimacy, of our adversary process.” 477 U. S., at 374. We observed that because a violation of the right would often go unremedied except on collateral review, “restricting the litigation of some Sixth Amendment claims to trial and direct review would seriously interfere with an accused’s right to effective representation.” Id., at 378.
In this case, the argument for extending Stone again falls short.4 To understand why, a brief review of the derivation of the Miranda safeguards, and the purposes they were designed to serve, is in order.
The Self-Incrimination Clause of the Fifth Amendment guarantees that no person “shall be compelled in any criminal case to be a witness- against himself.” U. S. Const., Arndt. 5. In Brain v. United States, 168 U. S. 532 (1897), the Court held that the Clause barred the introduction in federal cases of involuntary confessions made in response to custodial interrogation. We did not recognize the Clause’s applicability to state cases until 1964, however, see Malloy v. Hogan, 378 U. S. 1; and, over the course of 30 years, beginning with the decision in Brown v. Mississippi, 297 U. S. 278 (1936), we analyzed the admissibility of confessions in such cases as a question of due process under the Fourteenth Amendment. See Stone, The Miranda Doctrine in the Burger Court, 1977 S. Ct. Rev. 99, 101-102. Under this ap*689proach, we examined the totality of circumstances to determine whether a confession had been “ ‘made freely, voluntarily and without compulsion or inducement of any sort.’” Haynes v. Washington, 373 U. S. 503, 513 (1963) (quoting Wilson v. United States, 162 U. S. 613, 623 (1896)); see also Schneckloth v. Bustamante, supra, at 223-227 (discussing totality-of-circumstances approach). See generally 1 W. LaFave & J. Israel, Criminal Procedure § 6.2 (1984). Indeed, we continue to employ the totality-of-circumstances approach when addressing a claim that the introduction of an involuntary confession has violated due process. E.g., Arizona v. Fulminante, 499 U. S. 279 (1991); Miller v. Fenton, 474 U. S. 104, 109-110 (1985).
In Malloy, we recognized that the Fourteenth Amendment incorporates the Fifth Amendment privilege against self-incrimination, and thereby opened Bram’s doctrinal avenue for the analysis of state cases. So it was that two years later we held in Miranda that the privilege extended to state custodial interrogations. In Miranda, we spoke of the privilege as guaranteeing a person under interrogation “the right ‘to remain silent unless he chooses to speak in the unfettered exercise of his own will,’ ” 384 U. S., at 460 (quoting Malloy, supra, at 8), and held that “without proper safeguards the process of in-custody interrogation . . . contains inherently compelling pressures which work to undermine the individual’s will to resist and to compel him to speak where he would not otherwise do so freely.” 384 U. S., at 467. To counter these pressures we prescribed, absent “other fully effective means,” the now-familiar measures in aid of a defendant’s Fifth Amendment privilege:
“He must be warned prior to any questioning that he has the right to remain silent, that anything he says can be used against him in a court of law, that he has the right to the presence of an attorney, and that if he cannot afford an attorney one will be appointed for him prior to any questioning if he so desires. Opportunity *690to exercise these rights must be afforded to him throughout the interrogation. After such warnings have been given, and such opportunity afforded him, the individual may knowingly and intelligently waive these rights and agree to answer questions or make a statement.” Id., at 479.
Unless the prosecution can demonstrate the warnings and waiver as threshold matters, we held, it may not overcome an objection to the use at trial of statements obtained from the person in any ensuing custodial interrogation. See ibid.; cf. Oregon v. Hass, 420 U. S. 714, 721-723 (1975) (permitting use for impeachment purposes of statements taken in violation of Miranda).
Petitioner, supported by the United States as amicus curiae, argues that Miranda’s safeguards are not constitutional in character, but merely “prophylactic,” and that in consequence habeas review should not extend to a claim that a state conviction rests on statements obtained in the absence of those safeguards. Brief for Petitioner 91-93; Brief for United States as Amicus Curiae 14-15. We accept petitioner’s premise for purposes of this case, but not her conclusion.
The Miranda Court did of course caution that the Constitution requires no “particular solution for the inherent compulsions of the interrogation process,” and left it open to a State to meet its burden by adopting “other procedures . . . at least as effective in apprising accused persons” of their rights. 384 U. S., at 467. The Court indeed acknowledged that, in barring introduction of a statement obtained without the required warnings, Miranda might exclude a confession that we would not condemn as “involuntary in traditional terms,” id., at 457, and for this reason we have sometimes called the Miranda safeguards “prophylactic” in nature. E. g., Duckworth v. Eagan, 492 U. S. 195, 203 (1989); Connecticut v. Barrett, 479 U. S. 523, 528 (1987); Oregon v. Elstad, 470 U. S. 298, 305 (1985); New York v. Quarles, 467 U. S. 649, 654 (1984); see Michigan v. Tucker, 417 U. S. 433, 444 (1974) *691(Miranda Court “recognized that these procedural safeguards were not themselves rights protected by the Constitution but were instead measures to insure that the right against compulsory self-incrimination was protected”)- But cf. Quarles, supra, at 660 (opinion of O’Connor, J.) (Miranda Court “held unconstitutional, because inherently compelled, the admission of statements derived from in-custody questioning not preceded by an explanation of the privilege against self-incrimination and the consequences of forgoing it”). Calling the Miranda safeguards “prophylactic,” however, is a far cry from putting Miranda on all fours with Mapp, or from rendering Miranda subject to Stone.
As we explained in Stone, the Mapp rule “is not a personal constitutional right,” but serves to deter future constitutional violations; although it mitigates the juridical consequences of invading the defendant’s privacy, the exclusion of evidence at trial can do nothing to remedy the completed and wholly extrajudicial Fourth Amendment violation. Stone, 428 U. S., at 486. Nor can the Mapp rule be thought to enhance the soundness of the criminal process by improving the reliability of evidence introduced at trial. Quite the contrary, as we explained in Stone, the evidence excluded under Mapp “is typically reliable and often the most probative information bearing on the guilt or innocence of the defendant:” 428 U. S., at 490.
Miranda differs from Mapp in both respects. “Prophylactic” though it may be, in protecting a defendant’s Fifth Amendment privilege against self-incrimination, Miranda safeguards “a fundamental trial right.” United States v. Verdugo-Urquidez, 494 U. S. 259, 264 (1990) (emphasis added); cf. Kimmelman, 477 U. S., at 377 (Stone does not bar habeas review of claim that the personal trial right to effective assistance of counsel has been violated). The privilege embodies “principles of humanity and civil liberty, which had been secured in the mother country only after years of struggle,” Bram, 168 U. S., at 544, and reflects
*692“many of our fundamental values and most noble aspirations: ... our preference for an accusatorial rather than an inquisitorial system of criminal justice; our fear that self-incriminating statements will be elicited by inhumane treatment and abuses; our sense of fair play which dictates ‘a fair state-individual balance by requiring the government to leave the individual alone until good cause is shown for disturbing him and by requiring the government in its contest with the individual to shoulder the entire load;’ our respect for the inviolability of the human personality and of the right of each individual ‘to a private enclave where he may lead a private life;’ our distrust of self-deprecatory statements; and our realization that the privilege, while sometimes ‘a shelter to the guilty,’ is often ‘a protection to the innocent.’” Murphy v. Waterfront Comm’n of New York Harbor, 378 U. S. 52, 55 (1964) (citations omitted).
Nor does the Fifth Amendment “trial right” protected by Miranda serve some value necessarily divorced from the correct ascertainment of guilt. “ ‘[A] system of criminal law enforcement which comes to depend on the “confession” will, in the long run, be less reliable and more subject to abuses’ than a system relying on independent investigation. ” Michigan v. Tucker, supra, at 448, n. 23 (quoting Escobedo v. Illinois, 378 U. S. 478, 488-489 (1964)). By bracing against “the possibility of unreliable statements in every instance of in-custody interrogation,” Miranda serves to guard against “the use of unreliable statements at trial.” Johnson v. New Jersey, 384 U. S. 719, 730 (1966); see also Schneckloth, 412 U. S., at 240 {Miranda “Court made it clear that the basis for decision was the need to protect the fairness of the trial itself”); Halpern, Federal Habeas Corpus and the Mapp Exclusionary Rule after Stone v. Powell, 82 Colum. L. Rev. 1, 40 (1982); cf. Rose v. Mitchell, 443 U. S. 545 (1979) (Stone does not bar habeas review of claim of racial discrimination *693in selection of grand-jury foreman, as this claim goes to the integrity of the judicial process).
Finally, and most importantly, eliminating review of Miranda claims would not significantly benefit the federal courts in their exercise of habeas jurisdiction, or advance the cause of federalism in any substantial way. As one amicus concedes, eliminating habeas review of Miranda issues would not prevent a state prisoner from simply converting his barred Miranda claim into a due process claim that his conviction rested on an involuntary confession. See Brief for United States as Amicus Curiae 17. Indeed, although counsel could provide us with no empirical basis for projecting the consequence of adopting petitioner’s position, see Tr. of Oral Arg. 9-11,19-21, it seems reasonable to suppose that virtually all Miranda claims would simply be recast in this way.5
If that is so, the federal courts would certainly not have heard the last of Miranda on collateral review. Under the due process approach, as we have already seen, courts look to the totality of circumstances to determine whether a confession was voluntary. Those potential circumstances include not only the crucial element of police coercion, Colorado v. Connelly, 479 U. S. 157, 167 (1986); the length of the interrogation, Ashcraft v. Tennessee, 322 U. S. 143, 153-154 (1944); its location, see Reck v. Pate, 367 U. S. 433, 441 (1961); its continuity, Leyra v. Denno, 347 U. S. 556, 561 (1954); the defendant’s maturity, Haley v. Ohio, 332 U. S. 596, 599-601 (1948) (opinion of Douglas, J.); education, Clewis v. Texas, 386 U. S. 707, 712 (1967); physical condition, Greenwald v. Wisconsin, 390 U. S. 519, 520-521 (1968) (per curiam); and mental health, Fikes v. Alabama, 352 U. S. 191, 196 (1957). They also include the failure of police to advise the defendant of his rights to remain silent and to have counsel present *694during custodial interrogation. Haynes v. Washington, 373 U. S. 503, 516-517 (1963); Brief for United States as Amicus Curiae 19, n. 17; see also Schneckloth, supra, at 226 (discussing factors). We could lock the front door against Miranda, but not the back.
We thus fail to see how abdicating Miranda’s, bright-line (or, at least, brighter-line) rules in favor of an exhaustive totality-of-circumstances approach on habeas would do much of anything to lighten the burdens placed on busy federal courts. See P. Bator, D. Meltzer, P. Mishkin, & D. Shapiro, Hart and Wechsler’s The Federal Courts and the Federal System 188 (3d ed. 1988, Supp. 1992); Halpern, supra, at 40; Schulhofer, Confessions and the Court, 79 Mich. L. Rev. 865, 891 (1981); see also Quarles, 467 U. S., at 664 (O’Connor, J., concurring in judgment in part and dissenting in part) (quoting Fare v. Michael C, 439 U. S. 1310, 1314 (1978) (Rehnquist, J., in chambers)) (Miranda’s “ ‘core virtue’ ” was “ ‘affording] police and courts clear guidance on the manner in which to conduct a custodial investigation’ ”). We likewise fail to see how purporting to eliminate Miranda issues from federal habeas would go very far to relieve such tensions as Miranda may now raise between the two judicial systems. Relegation of habeas petitioners to straight involuntariness claims would not likely reduce the amount of litigation, and each such claim would in any event present a legal question requiring an “independent federal determination” on habeas. Miller v. Fenton, 474 U. S., at 112.
One might argue that tension results between the two judicial systems whenever a federal habeas court overturns a state conviction on finding that the state court let in a voluntary confession obtained by the police without the Miranda safeguards. And one would have to concede that this has occurred in the past, and doubtless will occur again. It is not reasonable, however, to expect such occurrences to be frequent enough to amount to a substantial cost of reviewing *695Miranda claims on habeas or to raise federal-state tensions to an appreciable degree. See Tr. of Oral Arg. 11, 21. We must remember in this regard that Miranda came down some 27 years ago. In that time, law enforcement has grown in constitutional as well as technological sophistication, and there is little reason to believe that the police today are unable, or even generally unwilling, to satisfy Miranda’s requirements. See Quarles, supra, at 663 (O’Connor, J., concurring in judgment in part and dissenting in part) (quoting Rhode Island v. Innis, 446 U. S. 291, 304 (1980) (Burger, C. J., concurring in judgment)) (“ ‘meaning of Miranda has become reasonably clear and law enforcement practices have adjusted to its strictures’ ”); Schuihofer, Reconsidering Miranda, 54 U. Chi. L. Rev. 435, 455-457 (1987).6 And if, finally, one should question the need for federal collateral review of requirements that merit such respect, the answer simply is that the respect is sustained in no small part by the existence of such review. “It is the occasional abuse that the federal writ of habeas corpus stands ready to correct.” Jackson, 443 U. S., at 322.
III
One final point should keep us only briefly. As he had done in his state appellate briefs, on habeas Williams raised only one claim going to the admissibility of his statements to the police: that the police had elicited those statements without satisfying the Miranda requirements. See supra, at 684. In her answer, petitioner addressed only that claim. See Brief in Support of Answer in No. 90CV-70256 DT, p. 3 (ED Mich.). The District Court, nonetheless, without an eviden-tiary hearing or even argument, went beyond the habeas petition and found the statements Williams made after re*696ceiving the Miranda warnings to be involuntary under due process criteria. Before the Court of Appeals, petitioner objected to the District Court’s due process enquiry on the ground that the habeas petition’s reference to Miranda rights had given her insufficient notice to address a due process claim. Brief for Respondent-Appellant in No. 90-2289, p. 6 (CA6). Petitioner pursues the objection here. See Pet. for Cert. 1; Brief for Petitioner 14-15, n. 2.
Williams effectively concedes that his habeas petition raised no involuntariness claim, but he argues that the matter was tried by the implied consent of the parties under Federal Rule of Civil Procedure 15(b),7 and that petitioner can demonstrate no prejudice from the District Court’s action. See Brief for Respondent 41-42, n. 22. The record, however, reveals neither thought, word, nor deed of petitioner that could be taken as any sort of consent to the determination of an independent due process claim, and petitioner was manifestly prejudiced by the District Court’s failure to afford her an opportunity to present evidence bearing on that claim’s resolution. The District Court should not have addressed the involuntariness question in these circumstances.8
*697> I — <
The judgment of the Court of Appeals is affirmed in part and reversed in part, and the case is remanded for further proceedings consistent with this opinion.
It is so ordered.
The District Court mistakenly believed that the trial court had allowed the introduction of the statements Williams had made on April 12, and its ruling consequently extended to those statements as well. App. to Pet. for Cert. 72a-75a.
Justice Scalia argues in effect that the rule in Stone v. Powell, 428 U. S. 465 (1976), should extend to all claims on federal habeas review. See post, at 719-720. With respect, that reasoning goes beyond the question on which we granted certiorari, Pet. for Cert. 1 (“where the premise of [a] Fifth Amendment ruling is a finding of a Miranda violation, where the petitioner has had one full and fair opportunity to raise the Miranda claim *686in state court, should collateral review of the same claim on a habeas corpus petition be precluded?”), and we see no good reason to address it in this case.
Title 28 U. S. C. § 2264(a) provides: “The Supreme Court, a Justice thereof, a circuit judge, or a district court shall entertain an application for a writ of habeas corpus in behalf of a person in custody pursuant to the judgment of a State court only on the ground that he is in custody in violation of the Constitution or laws or treaties of the United States.”
We have in the past declined to address the application of Stone in this context. See, e. g., Duckworth v. Eagan, 492 U. S. 195, 201, n. 3 (1989); Wainwright v. Sykes, 433 U. S. 72, 87, n. 11 (1977).
Justice O’Connor is confident that many such claims would be unjustified, see post, at 708-709, but that is beside the point. Justifiability is not much of a gatekeeper on habeas.
It should indeed come as no surprise that one of the submissions arguing against the extension of Stone in this case comes to us from law enforcement organizations. See Brief for Police Foundation et al. as Amici Curiae.
The relevant part of Rule 15(b) provides: “When issues not raised by the pleadings are tried by express or implied consent of the parties, they shall be treated in all respects as if they had been raised in the pleadings. Such amendment of the pleadings as may be necessary to cause them to conform to the evidence and to raise these issues may be made upon motion of any party at any time, even after judgment; but failure so to amend does not affect the result of the trial of these issues.” See 28 U. S. C. §2254 Rule 11 (application of Federal Rules of Civil Procedure to habeas petitions); 1 J. Liebman, Federal Habeas Corpus Practice and Procedure § 17.2 (1988) (Rule 15 applies in habeas actions).
We need not address petitioner’s arguments that Williams failed to exhaust the involuntariness claim in the state courts and that the District Court applied a new rule under Teague v. Lane, 489 U. S. 288 (1989). Of course, we also express no opinion on the merits of the involuntariness claim.