opinion: Justice Marshall
  announced the judgment of the Court and delivered the opinion of the Court with respect to Parts I and II and an opinion with respect to Parts III, IV, and V, in which Justice Brennan, Justice Blackmun, and Justice Stevens join.
  For centuries no jurisdiction has countenanced the execution of the insane, yet this Court has never decided whether the Constitution forbids the practice. Today we keep faith with our common-law heritage in holding that it does.
  H
  Alvin Bernard Ford was convicted of murder in 1974 and sentenced to death. There is no suggestion that he was incompetent at the time of his offense, at trial, or at sentencing. In early 1982, however, Ford began to manifest gradual changes in behavior. They began as an occasional peculiar idea or confused perception, but became more serious over time. After reading in the newspaper that the Ku Klux Klan had held a rally in nearby Jacksonville, Florida, Ford developed an obsession focused upon the Klan. His letters to various people reveal endless brooding about his “Klan work,” and an increasingly pervasive delusion that he had become the target of a complex conspiracy, involving the Klan and assorted others, designed to force him to commit suicide. He believed that the prison guards, part of the conspiracy, had been killing people and putting the bodies in the concrete enclosures used for beds. Later, he began to believe that his women relatives were being tortured and sexually abused somewhere in the prison. This notion developed into a delusion that the people who were tormenting him at the prison had taken members of Ford’s family hostage. The hostage delusion took firm hold and expanded, until Ford was reporting that 135 of his friends and family were being held hostage in the prison, and that only he could help them. By “day 287” of the “hostage crisis,” the list of hostages had expanded to include “senators, Senator Kennedy, and many other leaders.” App. 53. In a letter to the Attorney General of Florida, written in 1983, Ford appeared to assume authority for ending the “crisis,” claiming to have fired a number of prison officials. He began to refer to himself as “Pope John Paul, III,” and reported having appointed nine new justices to the Florida Supreme Court. Id., at 59.
  Counsel for Ford asked a psychiatrist who had examined Ford earlier, Dr. Jamal Amin, to continue seeing him and to recommend appropriate treatment. On the basis of roughly 14 months of evaluation, taped conversations between Ford and his attorneys, letters written by Ford, interviews with Ford’s acquaintances, and various medical records, Dr. Amin concluded in 1983 that Ford suffered from “a severe, uncontrollable, mental disease which closely resembles ‘Paranoid Schizophrenia With Suicide Potential’” — a “major mental disorder . . . severe enough to substantially affect Mr. Ford’s present ability to assist in the defense of his life.” Id., at 91.
  Ford subsequently refused to see Dr. Amin again, believing him to have joined the conspiracy against him, and Ford’s counsel sought assistance from Dr. Harold Kaufman, who interviewed Ford in November 1983. Ford told Dr. Kaufman that “I know there is some sort of death penalty, but I’m free to go whenever I want because it would be illegal and the executioner would be executed.” Id., at 65. When asked if he would be executed, Ford replied: “I can’t be executed because of the landmark case. I won. Ford v. State will prevent executions all over.” Id., at 66. These statements appeared amidst long streams of seemingly unrelated thoughts in rapid succession. Dr. Kaufman concluded that Ford had no understanding of why he was being executed, made no connection between the homicide of which he had been convicted and the death penalty, and indeed sincerely believed that he would not be executed because he owned the prisons and could control the Governor through mind waves. Id., at 67. Dr. Kaufman found that there was “no reasonable possibility that Mr. Ford was dissembling, malingering or otherwise putting on a performance . . . .” Id., at 65. The following month, in an interview with his attorneys, Ford regressed further into nearly complete incomprehensibility, speaking only in a code characterized by intermittent use of the word “one,” making statements such as “Hands one, face one. Mafia one. God one, father one, Pope one. Pope one. Leader one.” Id., at 72.
  Counsel for Ford invoked the procedures of Florida law governing the determination of competency of a condemned inmate, Fla. Stat. § 922.07 (1985). Following the procedures set forth in the statute, the Governor of Florida appointed a panel of three psychiatrists to evaluate whether, under §922.07(2), Ford had “the mental capacity to understand the nature of the death penalty and the reasons why it was imposed upon him.” At a single meeting, the three psychiatrists together interviewed Ford for approximately 30 minutes. Each doctor then filed a separate two- or three-page report with the Governor, to whom the statute delegates the final decision. One doctor concluded that Ford suffered from “psychosis with paranoia” but had “enough cognitive functioning to understand the nature and the effects of the death penalty, and why it is to be imposed on him.” App. 103. Another found that, although Ford was “psychotic,” he did “know fully what can happen to him.” Id., at 105-106. The third concluded that Ford had a “severe adaptational disorder,” but did “comprehend his total situation including being sentenced to death, and all of the implications of that penalty.” Id., at 99-100. He believed that Ford’s disorder, “although severe, seem[ed] contrived and recently learned.” Id., at 100. Thus, the interview produced three different diagnoses, but accord on the question of sanity as defined by state law.
  The Governor’s decision was announced on April 30, 1984, when, without explanation or statement, he signed a death warrant for Ford’s execution. Ford’s attorneys unsuccessfully sought a hearing in state court to determine anew Ford’s competency to suffer execution. Ford v. Wainwright, 451 So. 2d 471, 475 (Fla. 1984). Counsel then filed a petition for habeas corpus in the United States District Court for the Southern District of Florida, seeking an evidentiary hearing on the question of Ford’s sanity, proffering the conflicting findings of the Governor-appointed commission and subsequent challenges to their methods by other psychiatrists. The District Court denied the petition without a hearing. The Court of Appeals granted a certificate of probable cause and stayed Ford’s execution, Ford v. Strickland, 734 F. 2d 538 (CA11 1984), and we rejected the State’s effort to vacate the stay of execution. Wainwright v. Ford, 467 U. S. 1220 (1984). The Court of Appeals then addressed the merits of Ford’s claim and a divided panel affirmed the District Court’s denial of the writ. 752 F. 2d 526 (CA11 1985). This Court granted Ford’s petition for certiorari in order to resolve the important issue whether the Eighth Amendment prohibits the execution of the insane and, if so, whether the District Court should have held a hearing on petitioner’s claim. 474 U. S. 1019 (1985).
  I — I
  Since this Court last had occasion to consider the infliction of the death penalty upon the insane, our interpretations of the Due Process Clause and the Eighth Amendment have evolved substantially. In Solesbee v. Balkcom, 339 U. S. 9 (1950), a condemned prisoner claimed a due process right to a judicial determination of his sanity, yet the Court did not consider the possible existence of a right under the Eighth Amendment, which had not yet been applied to the States. The sole question the Court addressed was whether Georgia’s procedure for ascertaining sanity adequately effectuated that State’s own policy of sparing the insane from execution. See also Caritativo v. California, 357 U. S. 549 (1958); United States ex rel. Smith v. Baldi, 344 U. S. 561 (1953); Phyle v. Duffy, 334 U. S. 431 (1948); Nobles v. Georgia, 168 U. S. 398 (1897). Now that the Eighth Amendment has been recognized to affect significantly both the procedural and the substantive aspects of the death penalty, the question of executing the insane takes on a wholly different complexion. The adequacy of the procedures chosen by a State to determine sanity, therefore, will depend upon an issue that this Court has never addressed: whether the Constitution places a substantive restriction on the State’s power to take the fife of an insane prisoner.
  There is now little room for doubt that the Eighth Amendment’s ban on cruel and unusual punishment embraces, at a minimum, those modes or acts of punishment that had been considered cruel and unusual at the time that the Bill of Rights was adopted. See Solem v. Helm, 463 U. S. 277, 285-286 (1983); id., at 312-313 (Burger, C. J., joined by White, Rehnquist, and O’Connor, JJ., dissenting); Fur-man v. Georgia, 408 U. S. 238, 264 (1972) (Brennan, J., concurring); McGautha v. California, 402 U. S. 183, 226 (1971) (Black, J., concurring). “Although the Framers may have intended the Eighth Amendment to go beyond the scope of its English counterpart, their use of the language of the English Bill of Rights is convincing proof that they intended to provide at least the same protection . . . .” Solern v. Helm, supra, at 286.
  Moreover, the Eighth Amendment’s proscriptions are not limited to those practices condemned by the common law in 1789. See Gregg v. Georgia, 428 U. S. 153, 171 (1976) (opinion of Stewart, Powell, and Stevens, JJ.). Not bound by the sparing humanitarian concessions of our forebears, the Amendment also recognizes the “evolving standards of decency that mark the progress of a maturing society.” Trap v. Dulles, 356 U. S. 86, 101 (1958) (plurality opinion). In addition to considering the barbarous methods generally outlawed in the 18th century, therefore, this Court takes into account objective evidence of contemporary values before determining whether a particular punishment comports with the fundamental human dignity that the Amendment protects. See Coker v. Georgia, 433 U. S. 584, 597 (1977) (plurality opinion).
  A
  We begin, then, with the common law. The bar against executing a prisoner who has lost his sanity bears impressive historical credentials; the practice consistently has been branded “savage and inhuman.” 4 W. Blackstone, Commentaries *24-*25 (hereinafter Blackstone). Blackstone explained:
  “[IJdiots and lunatics are not chargeable for their own acts, if committed when under these incapacities: no, not even for treason itself. Also, if a man in his sound memory commits a capital offence, and before arraignment for it, he becomes mad, he ought not to be arraigned for it: because he is not able to plead to it with that advice and caution that he ought. And if, after he has pleaded, the prisoner becomes mad, he shall not be tried: for how can he make his defence? If, after he be tried and found guilty, he loses his senses before judgment, judgment shall not be pronounced; and if, after judgment, he becomes of nonsane memory, execution shall be stayed: for peradventure, says the humanity of the English law, had the prisoner been of sound memory, he might have alleged something in stay of judgment or execution.” Ibid, (footnotes omitted).
  Sir Edward Coke had earlier expressed the same view of the common law of England: “[B]y intendment of Law the execution of the offender is for example, . . . but so it is not when a mad man is executed, but should be a miserable spectacle, both against Law, and of extream inhumanity and cruelty, and can be no example to others.” 3 E. Coke, Institutes 6 (6th ed. 1680) (hereinafter Coke). Other recorders of the common law concurred. See 1 M. Hale, Pleas of the Crown 36 (1736) (hereinafter Hale); 1 W. Hawkins, Pleas of the Crown 2 (7th ed. 1795) (hereinafter Hawkins); Hawles, Remarks on the Trial of Mr. Charles Bateman, 11 How. St. Tr. 474, 477 (1685) (hereinafter Hawles).
  As is often true of common-law principles, see 0. Holmes, The Common Law 5 (1881), the reasons for the rule are less sure and less uniform than the rule itself. One explanation is that the execution of an insane person simply offends humanity, Coke 6; another, that it provides no example to others and thus contributes nothing to whatever deterrence value is intended to be served by capital punishment. Ibid. Other commentators postulate religious underpinnings: that it is uncharitable to dispatch an offender “into another world, when he is not of a capacity to fit himself for it,” Hawles 477. It is also said that execution serves no purpose in these cases because madness is its own punishment: furiosus solo furore punitur. Blackstone *395. More recent commentators opine that the community’s quest for “retribution” — the need to offset a criminal act by a punishment of equivalent “moral quality” — is not served by execution of an insane person, which has a “lesser value” than that of the crime for which he is to be punished. Hazard & Louisell, Death, the State, and the Insane: Stay of Execution, 9 UCLA L. Rev. 381, 387 (1962). Unanimity of rationale, therefore, we do not find. “But whatever the reason of the law is, it is plain the law is so.” Hawles 477. We know of virtually no authority condoning the execution of the insane at English common law.
  Further indications suggest that this solid proscription was carried to America, where it was early observed that “the judge is bound” to stay the execution upon insanity of the prisoner. 1 J. Chitty, A Practical Treatise on the Criminal Law *761; see 1 F. Wharton, A Treatise on Criminal Law §59 (8th ed. 1880).
  B
  This ancestral legacy has not outlived its time. Today, no State in the Union permits the execution of the insane. It is clear that the ancient and humane limitation upon the State’s ability to execute its sentences has as firm a hold upon the jurisprudence of today as it had centuries ago in England. The various reasons put forth in support of the common-law restriction have no less logical, moral, and practical force than they did when first voiced. For today, no less than before, we may seriously question the retributive value of executing a person who has no comprehension of why he has been singled out and stripped of his fundamental right to life. See Note, The Eighth Amendment and the Execution of the Presently Incompetent, 32 Stan. L. Rev. 765, 777, n. 58 (1980). Similarly, the natural abhorrence civilized societies feel at killing one who has no capacity to come to grips with his own conscience or deity is still vivid today. And the intuition that such an execution simply offends humanity is evidently shared across this Nation. Faced with such widespread evidence of a restriction upon sovereign power, this Court is compelled to conclude that the Eighth Amendment prohibits a State from carrying out a sentence of death upon a prisoner who is insane. Whether its aim be to protect the condemned from fear and pain without comfort of understanding, or to protect the dignity of society itself from the barbarity of exacting mindless vengeance, the restriction finds enforcement in the Eighth Amendment.
  I — I 1 — I HH
  The Eighth Amendment prohibits the State from inflicting the penalty of death upon a prisoner who is insane. Petitioner’s allegation of insanity in his habeas corpus petition, if proved, therefore, would bar his execution. The question before us is whether the District Court was under an obligation to hold an evidentiary hearing on the question of Ford’s sanity. In answering that question, we bear in mind that, while the underlying social values encompassed by the Eighth Amendment are rooted in historical traditions, the manner in which our judicial system protects those values is purely a matter of contemporary law. Once a substantive right or restriction is recognized in the Constitution, therefore, its enforcement is in no way confined to the rudimentary process deemed adequate in ages past.
  A
  In a habeas corpus proceeding, “a federal evidentiary hearing is required unless the state-court trier of fact has after a full hearing reliably found the relevant facts.” Townsend v. Sain, 372 U. S. 293, 312-313 (1963). The habeas corpus statute, following this Court’s decision in Townsend, provides that, in general, “a determination after a hearing on the merits of a factual issue, made by a State court of competent jurisdiction . . . , shall be presumed to be correct,” and an evidentiary hearing not required. 28 U. S. C. § 2254(d). In this case, it is clear that no state court has issued any determination to which that presumption of correctness could be said to attach; indeed, no court played any role in the rejection of petitioner’s claim of insanity. Thus, quite simply, Townsend and §2254 require the District Court to grant a hearing de novo on that question.
  But our examination does not stop there. For even when a state court has rendered judgment, a federal court is obliged to hold an evidentiary hearing on habeas corpus if, among other factors, “the factfinding procedure employed by the State court was not adequate to afford a full and fair hearing,” § 2254(d)(2); or “the material facts were not adequately developed at the State court hearing,” § 2254(d)(3); or “the applicant did not receive a full, fair, and adequate hearing in the State court proceeding.” § 2254(d)(6). If federal factfinding is to be avoided, then, in addition to providing a court judgment on the constitutional question, the State must also ensure that its procedures are adequate for the purpose of finding the facts.
  B
  The adequacy of a state-court procedure under Townsend is largely a function of the circumstances and the interests at stake. In capital proceedings generally, this Court has demanded that factfinding procedures aspire to a heightened standard of reliability. See, e. g., Spaziano v. Florida, 468 U. S. 447, 456 (1984). This especial concern is a natural consequence of the knowledge that execution is the most irremediable and unfathomable of penalties; that death is different. See Woodson v. North Carolina, 428 U. S. 280, 305 (1976) (opinion of Stewart, Powell, and Stevens, JJ.).
  Although the condemned prisoner does not enjoy the same presumptions accorded a defendant who has yet to be convicted or sentenced, he has not lost the protection of the Constitution altogether; if the Constitution renders the fact or timing of his execution contingent upon establishment of a further fact, then that fact must be determined with the high regard for truth that befits a decision affecting the life or death of a human being. Thus, the ascertainment of a prisoner’s sanity as a predicate to lawful execution calls for no less stringent standards than those demanded in any other aspect of a capital proceeding. Indeed, a particularly acute need for guarding against error inheres in a determination that “in the present state of the mental sciences is at best a hazardous guess however conscientious.” Solesbee v. Balkcom, 339 U. S., at 23 (Frankfurter, J., dissenting). That need is greater still because the ultimate decision will turn on the finding of a single fact, not on a range of equitable considerations. Cf. Woodson v. North Carolina, supra, at 304. In light of these concerns, the procedures employed in petitioner’s case do not fare well.
  C
  Florida law directs the Governor, when informed that a person under sentence of death may be insane, to stay the execution and appoint a commission of three psychiatrists to examine the prisoner. Fla. Stat. §922.07 (1985 and Supp. 1986). “The examination of the convicted person shall take place with all three psychiatrists present at the same time.” Ibid. After receiving the report of the commission, the Governor must determine whether “the convicted person has the mental capacity to understand the nature of the death penalty and the reasons why it was imposed on him.” Ibid. If the Governor finds that the prisoner has that capacity, then a death warrant is issued; if not, then the prisoner is committed to a mental health facility. The procedure is conducted wholly within the executive branch, ex parte, and provides the exclusive means for determining sanity. Ford v. Wainwright, 451 So. 2d, at 475.
  Petitioner received the statutory process. The Governor selected three psychiatrists, who together interviewed Ford for a total of 30 minutes, in the presence of eight other people, including Ford’s counsel, the State’s attorneys, and correctional officials. The Governor’s order specifically directed that the attorneys should not participate in the examination in any adversarial manner. This order was consistent with the present Governor’s “publicly announced policy of excluding all advocacy on the part of the condemned from the process of determining whether a person under a sentence of death is insane.” Goode v. Wainwright, 448 So. 2d 999, 1001 (Fla. 1984).
  After submission of the reports of the three examining psychiatrists, reaching conflicting diagnoses but agreeing on the ultimate issue of competency, Ford’s counsel attempted to submit to the Governor some other written materials, including the reports of the two other psychiatrists who had examined Ford at greater length, one of whom had concluded that the prisoner was not competent to suffer execution. The Governor’s office refused to inform counsel whether the submission would be considered. The Governor subsequently issued his decision in the form of a death warrant. That this most cursory form of procedural review fails to achieve even the minimal degree of reliability required for the protection of any constitutional interest, and thus falls short of adequacy under Townsend, is self-evident.
  IV
  A
  The first deficiency in Florida’s procedure lies in its failure to include the prisoner in the truth-seeking process. Notwithstanding this Court’s longstanding pronouncement that “[t]he fundamental requisite of due process of law is the opportunity to be heard,” Grannis v. Órdean, 234 U. S. 385, 394 (1914), state practice does not permit any material relevant to the ultimate decision to be submitted on behalf of the prisoner facing execution. In all other proceedings leading to the execution of an accused, we have said that the factfinder must “have before it all possible relevant information about the individual defendant whose fate it must determine.” Jurek v. Texas, 428 U. S. 262, 276 (1976) (plurality opinion). And we have forbidden States to limit the capital defendant’s submission of relevant evidence in mitigation of the sentence. Skipper v. South Carolina, 476 U. S. 1, 8 (1986); Lockett v. Ohio, 438 U. S. 586, 604 (1978) (joint opinion). It would be odd were we now to abandon our insistence upon unfettered presentation of relevant information, before the final fact antecedent to execution has been found.
  Rather, consistent with the heightened concern for fairness and accuracy that has characterized our review of the process requisite to the taking of a human life, we believe that any procedure that precludes the prisoner or his counsel from presenting material relevant to his sanity or bars consideration of that material by the factfinder is necessarily inadequate. “[T]he minimum assurance that the life-and-death guess will be a truly informed guess requires respect for the basic ingredient of due process, namely, an opportunity to be allowed to substantiate a claim before it is rejected.” Solesbee v. Balkcom, supra, at 23 (Frankfurter, J., dissenting).
  We recently had occasion to underscore the value to be derived from a factfinder’s consideration of differing psychiatric opinions when resolving contested issues of mental state. In Ake v. Oklahoma, 470 U. S. 68 (1985), we recognized that, because “psychiatrists disagree widely and frequently on what constitutes mental illness [and] on the appropriate diagnosis to be attached to given behavior and symptoms,” the factfinder must resolve differences in opinion within the psychiatric profession “on the basis of the evidence offered by each party” when a defendant’s sanity is at issue in a criminal trial. Id., at 81. The same holds true after conviction; without any adversarial assistance from the prisoner’s representative — especially when the psychiatric opinion he proffers is based on much more extensive evaluation than that of the state-appointed commission — the factfinder loses the substantial benefit of potentially probative information. The result is a much greater likelihood of an erroneous decision.
  B
  A related flaw in the Florida procedure is the denial of any opportunity to challenge or impeach the state-appointed psychiatrists’ opinions. “[C]ross-examination ... is beyond any doubt the greatest legal engine ever invented for the discovery of truth.” 5 J. Wigmore, Evidence § 1367 (J. Chadbourn rev. 1974). Cross-examination of the psychiatrists, or perhaps a less formal equivalent, would contribute markedly to the process of seeking truth in sanity disputes by bringing to light the bases for each expert’s beliefs, the precise factors underlying those beliefs, any history of error or caprice of the examiner, any personal bias with respect to the issue of capital punishment, the expert’s degree of certainty about his or her own conclusions, and the precise meaning of ambiguous words used in the report. Without some questioning of the experts concerning their technical conclusions, a factfinder simply cannot be expected to evaluate the various opinions, particularly when they are themselves inconsistent. See Barefoot v. Estelle, 463 U. S. 880, 899 (1983). The failure of the Florida procedure to afford the prisoner’s representative any opportunity to clarify or challenge the state experts’ opinions or methods creates a significant possibility that the ultimate decision made in reliance on those experts will be distorted.
  c
  Perhaps the most striking defect in the procedures of Fla. Stat. §922.07 (1985 and Supp. 1986), as noted earlier, is the State’s placement of the decision wholly within the executive branch. Under this procedure, the person who appoints the experts and ultimately decides whether the State will be able to carry out the sentence that it has long sought is the Governor, whose subordinates have been responsible for initiating every stage of the prosecution of the condemned from arrest through sentencing. The commander of the State’s corps of prosecutors cannot be said to have the neutrality that is necessary for reliability in the factfinding proceeding.
  Historically, delay of execution on account of insanity was not a matter of executive clemency (ex mandato regis) or judicial discretion (ex arbitrio judiéis); rather, it was required by law (ex necessitate legis). 1 N. Walker, Crime and Insanity in England 196 (1968). Thus, history affords no better basis than does logic for placing the final determination of a fact, critical to the trigger of a constitutional limitation upon the State’s power, in the hands of the State’s own chief executive. In no other circumstance of which we are aware is the vindication of a constitutional right entrusted to the unreviewable discretion of an administrative tribunal.
  V
  A
  Having identified various failings of the Florida scheme, we must conclude that the State’s procedures for determining sanity are inadequate to preclude federal redetermination of the constitutional issue. We do not here suggest that only a full trial on the issue of sanity will suffice to protect the federal interests; we leave to the State the task of developing appropriate ways to enforce the constitutional restriction upon its execution of sentences. It may be that some high threshold showing on behalf of the prisoner will be found a necessary means to control the number of nonmeritorious or repetitive claims of insanity. Cf. Pate v. Robinson, 383 U. S. 375, 387 (1966) (hearing on competency to stand trial required if “sufficient doubt” of competency exists). Other legitimate pragmatic considerations may also supply the boundaries of the procedural safeguards that feasibly can be provided.
  Yet the lodestar of any effort to devise a procedure must be the overriding dual imperative of providing redress for those with substantial claims and of encouraging accuracy in the factfinding determination. The stakes are high, and the “evidence” will always be imprecise. It is all the more important that the adversary presentation of relevant information be as unrestricted as possible. Also essential is that the manner of selecting and using the experts responsible for producing that “evidence” be conducive to the formation of neutral, sound, and professional judgments as to the prisoner’s ability to comprehend the nature of the penalty. Fidelity to these principles is the solemn obligation of a civilized society.
  B
  Today we have explicitly recognized in our law a principle that has long resided there. It is no less abhorrent today than it has been for centuries to exact in penance the life of one whose mental illness prevents him from comprehending the reasons for the penalty or its implications. In fight of the clear need for trustworthiness in any factual finding that will prevent or permit the carrying out of an execution, we hold that Fla. Stat. §922.07 (1985 and Supp. 1986) provides inadequate assurances of accuracy to satisfy the requirements of Townsend v. Sain, 372 U. S. 293 (1963). Having been denied a factfinding procedure “adequate to afford a full and fair hearing” on the critical issue, 28 U. S. C. § 2254(d)(2), petitioner is entitled to an evidentiary hearing in the District Court, de novo, on the question of his competence to be executed. Townsend v. Sain, swpra, at 312.
  The judgment of the Court of Appeals is reversed, and the case is remanded for further proceedings consistent with this opinion.
  It is so ordered.
  At one point, Henry VIII enacted a law requiring that if a man convicted of treason fell mad, he should nevertheless be executed. 33 Hen. VIII, eh. 20. This law was uniformly condemned. See Blackstone *25; 1 Hale 35; 1 Hawkins 2. The “cruel and inhumane Law lived not long, but was repealed, for in that point also it was against the Common Law . . . .” Coke 6.
  Of the 50 States, 41 have a death penalty or statutes governing execution procedures. Of those, 26 have statutes explicitly requiring the suspension of the execution of a prisoner who meets the legal test for incompetence. See Ala. Code § 15-16-23 (1982); Ariz. Rev. Stat. Ann. § 13-4023 (1978); Ark. Stat. Ann. §43-2622 (1977); Cal. Penal Code Ann. §3703 (West 1982); Colo. Rev. Stat. § 16-8-112(2) (Supp. 1985); Conn. Gen. Stat. §54-101 (1985); Fla. Stat. §922.07 (1985 and Supp. 1986); Ga. Code Ann. § 17-10-62 (1982); Ill. Rev. Stat., ch. 38, ¶ 1005-2-3 (1982); Kan. Stat. Ann. §22-4006(3) (1981); Ky. Rev. Stat §431.240(2) (1985); Md. Ann. Code, Art. 27, § 75(c) (Supp. 1985); Miss. Code Ann. §99-19-57(2) (Supp. 1985); Mo. Rev. Stat §552.060 (1978); Mont. Code Ann. §46-14-221 (1984); Neb. Rev. Stat. §29-2537 (1979); Nev. Rev. Stat. §176.445 (1985); N. J. Stat. Ann. §30:4-82 (West 1981); N. M. Stat. Ann. §31-14-6 (1984); N. Y. Corree. Law § 656 (McKinney Supp. 1986); N. C. Gen. Stat. § 15A-1001 (1983); Ohio Rev. Code Ann. §2949.29 (1982); Okla. Stat., Tit. 22, §1008 (1986); S. D. Codified Laws §23A-27A-24 (1979); Utah Code Ann. §77-19-13 (1982); Wyo. Stat. §7-13-901 (Supp. 1986). Others have adopted the common-law rule by judicial decision. See State v. Allen, 204 La. 513, 515, 15 So. 2d 870, 871 (1943); Commonwealth v. Moon, 383 Pa. 18, 22-23,117 A. 2d 96, 99 (1955); Jordan v. State, 124 Tenn. 81, 89-90 135 S. W. 327, 329 (1911); State v. Davis, 6 Wash. 2d 696, 717, 108 P. 2d 641, 651 (1940). Still others have more discretionary statutory procedures providing for the suspension of sentence and transfer to mental facilities for convicted prisoners who have developed mental illness. See Del. Code Ann., Tit. 11, §406 (1979); Ind. Code § 11-10-4-2 (1982); Mass. Gen. Laws, ch. 279, §62 (1984); R. I. Gen. Laws §40.1-5.3-7 (1984); S. C. Code §44-23-220 (1985); Tex. Code Crim. Proc. Ann., Art. 46.01 (1979); Va. Code § 19.2-177 (1983). The remaining four States having a death penalty have no specific procedure governing insanity, but have not repudiated the common-law rule.
  The adequacy of the factfinding procedures is further called into question by the cursory nature of the underlying psychiatric examination itself. While this Court does not purport to set substantive guidelines for the development of expert psychiatric opinion, ef. Barefoot v. Estelle, 463 U. S. 880, 903 (1983), we can say that the goal of reliability is unlikely to be served by a single group interview, with no provision for the exercise of the psychiatrists’ professional judgment regarding the possible need for different or more comprehensive evaluative techniques. The inconsistency and vagueness of the conclusions reached by the three examining psychiatrists in this case attest to the dubious value of such an examination.
  Instructive analogies may be found in the State’s own procedures for determining'whether a defendant is competent to stand trial, Fla. Stat. §§916.11-916.12 (1986 and Supp. 1986), or in the comprehensive safeguards that Florida ensures to those subjected to involuntary commitment proceedings, Fla. Stat. §394.467 (1986). The parties’ interests are of course somewhat different in those contexts; nevertheless, all such inquests share the common goal of reaching a fair assessment of the subject’s mental state.
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