opinion: Per Curiam.
  The State of Nevada has moved to vacate an order of the Court of Appeals for the Ninth Circuit granting a stay of the execution of Thomas E. Baal. We grant the State’s motion to vacate the stay.
  I
  Thomas E. Baal was convicted and sentenced to death in Nevada District Court for first-degree murder and robbery with use of a deadly weapon. Evidence indicated that after attempting to rob Frances P. Maves, Baal stabbed her numerous times, took her car, and fled. Maves was pronounced dead some hours later. Police officers arrested Baal in Reno on February 28, 1988. After being given his Miranda warnings, Baal confessed to the robbery and murder.
  In March 1988, two psychiatrists examined Baal and found that Baal was competent to stand trial, able to understand right from wrong at the time of the alleged offense, and disturbed but not psychotic. In June 1988, Baal was arraigned and pleaded not guilty and not guilty by reason of insanity. A third psychiatrist, Dr. O’Gorman, was appointed to examine Baal, and, following an examination on August 31, 1988, concluded that Baal was competent to stand trial. On September 22, 1988, Baal pleaded guilty to first-degree murder and to robbery, both with use of a deadly weapon. A three-judge panel unanimously sentenced Baal to death. The Nevada Supreme Court affirmed Baal’s conviction and sentence, rejecting Baal’s contention that he was incompetent to enter a guilty plea and that it was error not to conduct a competency hearing prior to accepting his pleas. Baal v. State, 106 Nev. 69, 787 P. 2d 391 (1990).
  Baal filed a petition for state postconviction relief, but, prior to the hearing, changed his mind and withdrew the petition. On May 24, 1990, the state postconviction court held an evidentiary hearing to determine Baal’s competency. At that hearing, Baal testified that he did not want to continue any postconviction proceedings. He further testified that he knew the date he would be put to death, the reason he would be put to death, and that his waiver of postconviction relief would result in his death. A state psychiatrist testified that Baal was competent; a state prison official who had observed Baal also testified as to Baal’s competence. The court also reviewed the reports of three psychiatrists who had examined Baal and concluded that he was competent to stand trial. Based on this evidence, the court held that Baal was aware of his impending execution and of the reason for it, and thus was sane under the test set forth in Ford v. Wainwright, 477 U. S. 399 (1986). The court further held that Baal was in control of his faculties, was competent to choose to decline to pursue an appeal, and had made an intelligent waiver of his right to pursue postconviction relief.
  Approximately one week later, on May 31, 1990, and hours before Baal’s scheduled execution, Edwin and Doris Baal (Baal’s parents) filed a petition for federal habeas corpus relief as “next friend” of Thomas E. Baal. As one of their grounds for relief, petitioners asserted: “Thomas Baal is not competent to waive federal review of his claims.” In support of this claim, petitioners relied on an affidavit of a nonexamining psychiatrist, Dr. Jerry Howie, and an affidavit of Doris Baal.
  The United States District Court conducted a hearing and denied petitioners’ application for stay of execution, holding that, under this Court’s recent decision in Whitmore v. Arkansas, ante, p. 149, petitioners had failed to establish that the court had jurisdiction to entertain the petition. According to the District Court, petitioners had not provided an adequate explanation of why Baal could not appear on his own behalf to prosecute this action. Upon review of the record, the court found that all the evidence, other than the newly submitted affidavit of Dr. Howie, established that Baal was legally competent to understand the nature and consequences of his act and to represent his own interests in these proceedings. The court determined that Dr. Howie’s affidavit was not based on a first-hand examination, was conclusory, and was insufficient to warrant a psychiatric hearing or additional psychiatric examinations of Baal. The court subsequently denied petitioners’ motion for a certificate of probable cause. Petitioners appealed to the Court of Appeals for the Ninth Circuit.
  A divided panel of the Court of Appeals granted petitioners’ certificate of probable cause and stayed Thomas Baal’s execution. That court held that petitioners had made “some minimum showing of [Baal’s] incompetence” and evidence in the record provided “at least an arguable basis for finding that a full evidentiary hearing on competence should have been held by the district court.” Order in Baal v. Godinez, No. 90-15716 (CA9, June 2, 1990), pp. 3, 5. Judge Kozinski, in dissent, asserted that there was no substantial evidence of Baal’s incompetence to warrant a further evidentiary hearing or to upset the Nevada District Court’s finding that Baal was competent, which is entitled to a presumption of correctness upon federal habeas review. Dissent, at 6, 7.
  II
  In Whitmore v. Arkansas, ante, at 165, we held that “one necessary condition for ‘next friend’ standing in federal court is a showing by the proposed ‘next friend’ that the real party in interest is unable to litigate his own cause due to mental incapacity.” See also Rosenberg v. United States, 346 U. S. 273, 291 (1953). This prerequisite is not satisfied “where an evidentiary hearing shows that the defendant has given a knowing, intelligent, and voluntary waiver of his right to proceed.” Whitmore, ante, at 165. In Whitmore, we relied on the competency findings made by the Arkansas Supreme Court and concluded that Whitmore lacked next-friend standing in federal court. Ante, at 165-166. In this case, the state court held such an evidentiary hearing just one week before petitioners brought this petition for habeas corpus. After reviewing the evidence and questioning Baal, the state court concluded that Baal had intelligently waived his right to pursue postconviction relief.
  A state court’s determinations on the merits of a factual issue are entitled to a presumption of correctness on federal habeas review. A federal court may not overturn such determinations unless it concludes that they are not “fairly supported by the record.” See 28 U. S. C. § 2254(d)(8). We have held that a state court’s conclusion regarding a defendant’s competency is entitled to such a presumption. Maggio v. Fulford, 462 U. S. 111, 117 (1983). In this case, the state court’s conclusion that Baal was competent to waive his right to further proceedings was “fairly supported by the record.” Three psychiatrists who examined Baal had determined he was competent; a psychiatrist who had the opportunity to observe and talk to Baal testified that Baal was competent at the hearing; and the trial court concluded that Baal was competent after both observing Baal and questioning him extensively on the record. Accordingly, under §2254(d)’s presumption of correctness, the state court’s factual finding as to Baal’s competence is binding on a federal habeas court. See Maggio v. Fulford, supra; see also Marshall v. Lonberger, 459 U. S. 422 (1983) (§ 2254(d)’s presumption of correctness required federal habeas court to accept state court’s factual findings on the issue of respondent’s credibility).
  The state evidentiary hearing took place on May 24, 1990. When petitioners filed their habeas petition in District Court the following week, on May 31, 1990, the only new evidence presented to the court was the affidavit of Dr. Jerry Howie, a psychiatrist who had not examined Baal. In the affidavit, Dr. Howie stated that he had examined the reports of the psychiatrists who had found Baal competent to stand trial and a 1987 admission, evaluation, and discharge summary from the Hawaii State Hospital. Dr. Howie did not directly assert that Baal was incompetent. Rather, based only on these reports, and without any opportunity personally to observe Baal, the doctor concluded that “there is reason to believe this person may not be competent to waive his legal remedies.” Petition for Habeas Corpus in Baal v. Godinez, No. 90-243 (D. Nev.), Exhibit D (emphasis added). Cf. Rees v. Peyton, 384 U. S. 312, 313 (1966) (District Court directed to make a judicial determination of petitioner’s competence after psychiatrist examined him and “filed a detailed report concluding that [petitioner] was mentally incompetent”). As the District Court determined, this affidavit is “conclusory and lacking sufficient foundation or substance to warrant either a psychiatric hearing or additional psychiatric examination of the defendant.” Order in Baal v. Godinez, No. CV-N-90-243-HDM (D. Nev., May 31, 1990), p. 3. The District Court also reviewed the state-court record and the transcript of the state-court proceeding, as well as speaking with Baal at length via telephone. Based on its review, it concluded that petitioners had failed to establish that Baal was not competent to waive further proceedings. In the absence of any “meaningful evidence” of incompetency, Whitmore v. Arkansas, ante, at 166, the District Court correctly denied petitioners’ motion for a further evidentiary hearing on the question of Baal’s competence to waive his right to proceed.
  In holding that there was a “basis for finding that a full evidentiary hearing on competence should have been held,” Order in Baal v. Godinez, No. 90-15716 (CA9, June 2, 1990), p. 5, the Court of Appeals did not rely exclusively on the affidavit of Dr. Howie, the only evidence offered to indicate that Baal might have become incompetent at some time after the State’s evidentiary hearing. That affidavit, as noted, was not based on personal examination of Baal and stated only in conclusory and equivocal fashion that, based on his evaluation of the reports of the examining psychiatrists, Baal “may not be competent.” Rather, the Court of Appeals based its determination on the same evidence that had been before the State District Court — the reports of the three psychiatrists, the hospital report, and testimony regarding Baal’s prior suicide attempts. Indeed, because the Court of Appeals did not personally observe Baal, as the state court did, it had even less reason to overturn what is essentially a factual determination. See Maggio v. Fulford, supra, at 113. As there was no evidentiary basis for the Court of Appeal’s conclusion that the District Court erred in declining to conduct an evidentiary hearing, the stay granted by the court did not “reflect the presence of substantial grounds upon which relief might be granted.” Barefoot v. Estelle, 463 U. S. 880, 895 (1983).
  We realize that last minute petitions from parents of death row inmates may often be viewed sympathetically. But federal courts are authorized by the federal habeas statutes to interfere with the course of state proceedings only in specified circumstances. Before granting a stay, therefore, federal courts must make certain that an adequate basis exists for the exercise of federal power. In this case, that basis was plainly lacking. The State is entitled to proceed without federal intervention. Accordingly, we grant the State’s motion to vacate the stay entered by the Court of Appeals.
  It is so ordered.
  Justice Blackmun and Justice Stevens dissent and would deny the application to vacate the stay.
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