Affirmed by published opinion. Judge Shedd wrote the opinion, in which Judge WIDENER, Judge WILKINSON, Judge NIEMEYER, Judge LUTTIG, Judge WILLIAMS, and Judge DUNCAN joined. Judge WILKINSON wrote a separate concurring opinion. Judge WILLIAMS wrote a separate concurring opinion. Chief Judge WILKINS wrote a dissenting opinion, in which Judge MICHAEL, Judge MOTZ, Judge TRAXLER, Judge KING, and Judge GREGORY joined.
OPINION
SHEDD, Circuit Judge:
In 1996, Percy Levar Walton murdered three people in Danville, Virginia. Walton pled guilty to the crimes and was sentenced to death in Virginia, state court. Over the next several years, Walton directly appealed his conviction and then filed both state and federal habeas petitions, all of which were unsuccessful. In 2003, after the state court scheduled his execution date for the second time, Walton filed his second federal habeas petition wherein he asserted that he is both mentally incompetent and mentally retarded and, therefore, his execution is precluded under Ford v. Wainwright, 477 U.S. 399, 106 S.Ct. 2595, 91 L.Ed.2d 335 (1986) (prohibiting the execution of insane inmates), and Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002) (prohibiting the execution of mentally retarded inmates). The district court denied Walton’s habeas petition, and we now affirm.
We hold that the district court applied the proper legal standard in deciding that Walton is mentally competent to be executed, and its findings of fact are not clearly erroneous. We further hold that the district court properly dismissed Walton’s mental retardation claim because his habe-as petition fails to state sufficient facts demonstrating that he is mentally retarded under Virginia law.
I.
Walton murdered three people, an elderly couple and a younger man, in their homes in two separate incidents during November 1996.
Although the physical evidence alone overwhelmingly established Walton’s guilt, Walton also admitted to several other jail inmates that he committed the murders, and he described the graphic details of the murders to his cellmate. We previously recounted the facts of Walton’s crimes in greater detail in our opinion deciding Walton’s first federal habeas petition. See Walton v. Angelone, 321 F.3d 442, 446-49 (4th Cir.2003).
With the assistance of counsel, Walton pled guilty to all three murders, three counts of robbery, one count of burglary, and six counts of using a firearm in the commission of a felony. Walton indicated that he wanted to plead guilty because the “chair is for killers.” Id. at 454. After determining that Walton would likely commit additional criminal acts that would constitute a continuing serious threat to society, the Circuit Court for the City of Danville sentenced Walton to death.
Walton then began the long process of challenging his conviction and sentence on both direct and collateral review in state [163]*163and federal court. Our first federal habe-as opinion exhaustively details the extensive procedural history and the claims made in Walton’s numerous prior proceedings. See Id. at 450-52. In both his state and federal habeas petitions, Walton challenged his conviction and sentence on the ground, among many others, that he was not mentally competent to plead guilty.
After the district court denied Walton relief in his first habeas petition, Walton sought a certificate of appealability from this court. As to Walton’s claims that he was not competent to plead guilty and that his counsel was ineffective for failing to adequately raise the issue during the state trial court proceedings, we reviewed the extensive evidence regarding what Walton’s counsel knew about Walton’s mental condition during the trial court proceedings. Id. at 453-57. As we explained, shortly after Walton was indicted, the state court appointed a psychiatrist to assess Walton. Walton told the psychiatrist that he would be able to come back to life shortly after his execution with the same name but a new spirit. Walton also said that he would be able to resurrect his dead family members upon his return. Id. at 454 n. 12. This psychiatrist opined that Walton was competent to stand trial because Walton understood the proceedings against him and understood that, if convicted of capital murder, he could be executed in the electric chair or by lethal injection. Id. at 455-56. The state court appointed a second psychiatrist to assess Walton. The second psychiatrist also opined that Walton was competent because he understood the nature of the proeeed-ings against him and could assist his counsel. Id. at 456.
After conferring with these psychiatrists, Walton’s trial counsel decided against using a mental incompetence strategy at trial because, among other reasons, the testimony of the two psychiatrists would not have been helpful, Walton had told at least two of his fellow inmates that he intended to “play crazy,” and just a few months earlier Walton had stood trial for burglary and grand larceny and his competence to stand trial was not at issue then. Id. at 458.
After reviewing this evidence, we denied Walton’s certificate of appealability, concluding that “we harbor no doubt” that Walton was competent to plead guilty and that the assistance provided by Walton’s counsel was “more than reasonable.” Id. at 460-61. The United States Supreme Court denied Walton’s petition for a writ of certiorari. Walton v. Johnson, 539 U.S. 950, 123 S.Ct. 2626, 156 L.Ed.2d 642 (2003).
Thereafter, the Danville Circuit Court rescheduled Walton’s execution date for May 28, 2003.1 Walton chose electrocution as the form of execution. Just three days before this execution date, the district court granted Walton’s request for a stay of execution. A panel of this court granted Walton’s request to file a second habeas petition to allow him to claim (for the first time in any proceeding) that he cannot be executed because he is mentally retarded. In this second federal petition, Walton makes no further attack on his conviction. Walton’s only remaining claims are that he cannot be executed because (1) he is mentally retarded;2 and (2) he is mentally [164]*164incompetent.3
The district court dismissed Walton’s mental retardation claim without an evi-dentiary hearing, concluding that Walton failed to forecast evidence that his alleged mental retardation originated before the age of 18 — a required element under Virginia law. Walton v. Johnson, 269 F.Supp.2d 692, 700 (W.D.Va.2003). On the issue of mental competence, however, the district court determined that an evidentia-ry hearing was warranted. Id. at 694.
The district court heard extensive evidence regarding Walton’s mental competence during two days of testimony. On the first day, vastly conflicting testimony was presented. Walton’s retained experts, Drs. Anand Pandurangi and Reuben Gur, testified that Walton is suffering from schizophrenia and has borderline delusional ideas about his ability to come back to life after his execution.4 For instance, Walton told Dr. Pandurangi, chairman of the Division of Inpatient Psychiatry at the Medical College of Virginia, that, despite his impending death sentence, he wanted a motorcycle, a telephone, and to look good at the mall. In their discussion about death, Walton told him that “[p]eople who die go to the graveyard ... but everybody comes back.” J.A. 425. Despite Walton’s responses acknowledging that death does occur, Dr. Pandurangi ultimately opined that Walton does not comprehend that he is going to be executed and will die for murdering three people.
When Dr. Gur, the director of neuropsy-chology at the University of Pennsylvania, asked Walton what death meant, Walton responded, “It means you’re dead.” J.A. 441. Walton proceeded to explain, however, that after his execution he would “come back as a better person” and would “get a Burger King.” J.A. 441. Walton also told Dr. Gur that he had received a letter informing him of his May 28, 2003, execution date: “Yes, I have the letter, and I have an execution date.” J.A. 442. Dr. Gur testified that Walton said that execution means dying, but Walton’s main concern is that after his death he will come back as a woman. Based on his interviews with Walton, Dr. Gur concluded that although Walton “was able to discuss the method of execution in a seemingly rational fashion, [he] ... failed to comprehend that at the end of the procedure he will no longer be alive.” J.A. 466.
Walton also presented the testimony of Dr. Patricia General, a psychiatrist employed to assess Virginia inmates, who assessed Walton shortly before his scheduled [165]*1652003 execution date. Dr. General testified that Walton never exhibited any type of delusional behavior in her presence during their three interviews, but he was confused and largely unable to answer any of her questions during their first session. Dr. General’s initial impression was that Walton appeared floridly psychotic, but she did not believe she had a sufficient basis to prescribe him any medication. In their second interview, Dr. General asked Walton why he was going to be put to death. Walton responded that “some people had told him ... that he had killed some people.” J.A. 311-12. After Dr. General’s third and last interview with Walton, it was Dr. General’s impression that Walton, after receiving an explanation of what execution means, understood that he is going to die because he had been convicted of murder.
Walton also testified on the first day of the evidentiary hearing. He responded to many of the questions — even simple questions — by repeatedly saying, “I don’t know, I don’t even know.” This was the same response that he had used in varying degrees in interviews with all of the mental health experts who assessed him. Although Walton acknowledged that he had received a death sentence, he waffled in his answers about whether he had been given an execution date. When asked if he knew what would happen to him when he dies, Walton said that he did not know and that the question was “hard.” J.A. 508. Walton also denied knowing why the state was going to execute him, and he professed to having no recollection of the elderly couple he murdered. Walton acknowledged that execution by lethal injection involved having a needle stuck into your arm and that “you die,” but he denied knowing what would happen in the electric chair. J.A. 523.
Virginia’s evidence offered a different view of Walton’s mental condition. Shortly before his second scheduled execution date in May 2003, Walton was transferred to Greensville Correctional Center where Virginia’s electric chair is located. Allen Glasgow, a rehabilitation counselor at Greensville who conducts intake reviews when condemned inmates arrive at the facility, interviewed Walton when he arrived. Glasgow thought that Walton communicated well during their meeting, and he did not recall Walton ever using the phrase “I don’t know. I just don’t know” during the entire intake interview. During their interview, Glasgow discussed with Walton several documentary forms: a visitors list, an attorney list, a telephone call list, and a disposition of final remains designation form. Walton filled out the visitors list in his own handwriting with names and addresses from memory. Walton correctly wrote the name of his lawyer on the attorney list, but then indicated that he did not know her address. Glasgow explained that the final remains form was meant for Walton to select a person to dispose of his remains after his execution. Glasgow asked Walton if he understood the final remains form, Walton said that he understood it, and it was Glasgow’s impression that Walton did understand it. Walton told Glasgow that he wanted to put his mother’s name on the final remains form.
Virginia also presented the testimony of Dr. Alan Arikian, a psychiatrist employed to provide mental health service to Virginia inmates. Dr. Arikian began seeing Walton in 1999, several months before Drs. Pandurangi and Gur began seeing Walton. Unlike Drs. Pandurangi and Gur, who were retained to assess Walton regarding his claim that he is mentally incompetent, Dr. Arikian initially saw Walton regarding complaints made against him for disruptive behavior on his cellblock. According to Dr. Arikian, Walton exhibited no distur[166]*166bance of thought or mental illness of any kind when he first saw him. Walton did not use the phrase “I don’t know. I don’t even know” in their first session. When Dr. Arikian asked Walton about his disruptive behavior, Walton said, ‘Well, I just enjoy playing around with folks. I enjoy messing with them.” J.A. 553. Dr. Ariki-an met with Walton several more times during the months leading up to his first scheduled execution date in December 1999. In the early sessions, Walton carried on normal conversations with Dr. Ari-kian. In one conversation, Walton said that old people were expendable and that they should expect to be killed if they tried to keep him from taking their things that he wanted. Walton also said that he thought that “[execution is the same as murder,” and he seemed disappointed when Dr. Arikian did not express support for his comment. J.A. 556. Although Walton denied that he was on deathrow, Dr. Arikian did not believe Walton’s denial because it seemed inconsistent with the rest of their conversation.
As Walton’s December 1999 execution date drew near, however, Walton began to use the phrase “I don’t know. I just don’t know” in his conversations with Dr. Ariki-an even in response to simple matters. After Walton’s December 1999 execution date was stayed, Dr. Arikian did not see Walton again until 2003, shortly before his second scheduled execution date. Although Walton had become more subdued and less inclined to’ engage in conversation, Dr. Arikian does not believe that Walton is suffering from schizophrenia and instead believes Walton’s symptoms are more consistent with a person who has become completely indifferent, who “plays with each of us as the spirit moves him.... Some people he will respond to and some he won’t.” J.A. 578. Dr. Arikian testified that he believes that Walton understands that he will be executed as a result of being convicted of murder. When confronted with the directly opposing views of Drs. Pandu-rangi and Gur, Dr. Arikian responded: “I think we’re at opposite ends of the spectrum on that.... I think far from not having an understanding of what’s going on, I think [Walton] has a full understanding of what’s going on.” J.A. 579.
After hearing the divergent testimony regarding Walton’s mental competence, the district court decided to appoint a neutral expert to interview Walton and assess his mental condition. The district court attempted to obtain an expert agreeable to both sides by having each side appoint a psychiatrist who in turn advised the court on suitable neutral candidates. These two psychiatrists ultimately recommended Dr. Mark Mills, a highly qualified forensic psychiatrist, and the district court adopted their recommendation. Virginia later objected to the appointment of Dr. Mills after coming to believe that he could not be neutral because of his personal opposition to the death penalty. Virginia also noted that Walton’s counsel had previously retained Dr. Mills in another similar death penalty case. Walton’s counsel responded by assuring the district court that Dr. Mills could render objective opinions in Walton’s case. The district court overruled Virginia’s objection to the appoints ment of Dr. Mills and requested, based on its interpretation of Ford v. Wainwright, that Dr. Mills assess Walton and consider two issues: (1) whether Walton understands that he is to be punished by execution; and (2) whether Walton understands that his punishment is a consequence of his having been convicted of murdering three people.
After Dr. Mills interviewed Walton and submitted his report, the district court held a second evidentiary hearing. At the hearing, Dr. Mills testified that he found Walton to be “odd,” of low intelligence but [167]*167not mentally retarded, and probably suffering from a significant psychiatric disorder, quite possibly schizophrenia.5 According to Dr. Mills, a person suffering from schizophrenia can, nevertheless, be “competent to stand trial, competent to make a will, [and] competent to be executed.” J.A. 916. Notwithstanding Walton’s cognitive limitations, Dr. Mills stated that Walton was able to volunteer that he was in prison for murdering three people and that he was sentenced to be executed. Walton correctly informed Dr. Mills that he had selected electrocution for his execution. When Dr. Mills mentioned that many people would consider lethal injection preferable, Walton said that it did not matter because execution was “an end” or “the end.” J.A. 899.
Dr. Mills asked Walton about his religious views and his understanding of death. Walton responded that he believes that he will go to heaven and then come back in some form and be able to see his family. While Dr. Mills believes Walton has a very firm and clear belief in an “afterlife,” he does not believe that Walton is a person who is going to prepare for his death. J.A. 925. Even though Dr. Mills found Walton’s answers about death to be simple and even childlike, Dr. Mills nevertheless stated that he believes that Walton understands that after his death “things are going to be very different than they are now.” J.A. 902. Walton also told Dr. Mills that he prefers to live in prison for the rest of his life rather than be beaten to death. Dr. Mills admitted that he is philosophically opposed to the death penalty and that he would have preferred to find Walton not competent to be executed. Nevertheless, Dr. Mills stated that he “clearly believe[s]” that Walton understands that he is in prison for killing three people and that he will be executed as punishment for these crimes. J.A. 930.
The district court also allowed Walton to call Dr. Pandurangi to testify again because he had reassessed Walton a few days before the second hearing. Dr. Pan-durangi’s experience with Walton was different from Dr. Mills’ experience. Whereas Walton was able to volunteer to Dr. Mills that he was sentenced to be executed for killing three people, Walton told Dr. Pandurangi at the start of their interview that he did not know what the status of his case was. Dr. Pandurangi proceeded to inform Walton that he had pled guilty to killing three people and that he had been given a death sentence. In the next few moments, Walton was able to repeat this information when asked. However, about twenty minutes later, Dr. Pandurangi again asked Walton about his legal status, but this time Walton reverted to saying that he did not know. Although Dr. Pan-durangi stated that he does not think that Walton is overtly mentally retarded, he does believe that Walton thinks on the level of a child. When asked whether Walton would prepare for his death, Dr. Pan-durangi said that such a question would be difficult for him to answer but that he does not believe that Walton would be able to “wish[] people goodbye, turn[] off emotional relations, if he has any little belongings, who would get what.” J.A. 978. Based on his updated assessment, Dr. Pandurangi testified that he continues to believe that Walton suffers from schizophrenia. However, Dr. Pandurangi agrees with Dr. Mills that diagnosing an inmate [168]*168with schizophrenia does not necessarily mean that the inmate is mentally incompetent to be executed. Dr. Pandurangi also admitted that he has very little experience in making the type of competency assessment he was being called on to make in this case.
After both sides rested, the district court allowed final arguments. In addition to arguing other grounds for relief that were stated in Walton’s habeas petition, Walton’s counsel asserted for the first time that Walton, is not competent to be executed because he is “unable to spiritually prepare for his death.” J.A. 995.6
In a thorough opinion, the district court denied habeas relief on Walton’s mental incompetence claim, concluding that “Walton both understands that he is to be executed and that his execution is punishment for his conviction for murder.” Walton v. Johnson, 306 F.Supp.2d 597 (W.D.Va.2004). Walton now appeals.
II.
We first consider Walton’s mental incompetence claim. Walton argues that the district court erred by failing to follow the proper legal standard under Ford v. Wainwright. In the alternative, Walton argues that the district court’s factual determination that he understands that he has been sentenced to death for murdering three people is clearly erroneous.
A.
Walton first argues, based primarily on Ford, that the district court erred by using an incorrect test to determine his competency to be executed. We find Walton’s reliance on Ford misplaced.
The petitioner in Ford began exhibiting peculiar behavior after being sentenced to death for murder/ Ford’s lawyers retained mental health experts to assess his mental competence. After interviewing Ford, one expert opined that Ford “had no understanding of why he was being executed [and] made no connection between the homicide of which he had been convicted and the death penalty.” Ford, 477 U.S. at 403, 106 S.Ct. 2595. Based on this expert’s opinion, Ford’s lawyers sought a reprieve from the death penalty based on Ford’s incompetence.
At the time of Ford’s appeal — and still today — Florida law prohibited the execution of an inmate if he “does not have the mental capacity to understand the nature of the death penalty and why it was imposed on him.” FLA. STAT. ANN. § 922.07(3) (1985 & 2005). The Florida governor, who at that time had sole authority under Florida law to determine whether a death row inmate was competent to be executed,7 appointed three psychiatrists to assess Ford. After interviewing Ford in the same 30-minute interview, all three state-appointed psychiatrists concluded, consistent with the requirements of the Florida statute, that Ford was able “to understand the nature of the death penalty and the reasons why it was imposed upon him.” Ford, 477 U.S. at 403-04, 106 S.Ct. 2595. Although Ford’s lawyers submitted their psychiatrist’s report attesting that Ford was incompetent to be executed under the Florida standard, the governor, who had previously publicly announced [169]*169that he would not consider materials filed in support of a prisoner’s suggestion of incompetence, apparently did not accept the report for review. Id. at 413, 424, 106 S.Ct. 2595. Instead, the governor denied Ford’s request for relief without explanation and signed a death warrant. Ford filed a federal habeas petition, but the district court denied the petition without a hearing. Id. at 404, 106 S.Ct. 2595. After the circuit court affirmed, the Supreme Court granted Ford’s petition for certiora-ri.
In a fractured opinion, the five-member majority — consisting of a four-member plurality and a separate concurrence by Justice Powell — agreed on three matters: (1) the Eighth Amendment forbids the states from executing the insane, id. at 409-10, 418,106 S.Ct. 2595; (2) the Florida governor’s failure to consider the opinions of Ford’s psychiatrist violated his due process rights, id. at 413-16, 423-24, 106 S.Ct. 2595; and (3) Ford was entitled to an evidentiary hearing in federal district court. Id. at 418, 424-25, 106 S.Ct. 2595. In sum, the majority concluded that Florida failed to consider adequately all the evidence bearing on the question of whether Ford was competent under the Florida legal standard, i.e., whether Ford had “the mental capacity to understand the nature of the death penalty and the reasons why it was imposed on him.” Id. at 412, 106 S.Ct. 2595. The majority, however, did not decide that Florida’s legal standard for determining mental incompetence was inadequate. To the contrary, the four-member plurality recognized that Florida’s statute properly did not permit the execution of the insane. Id. at 408-09,106 S.Ct. 2595 n. 2. The plurality’s concern was not with Florida’s statutory incompetence standard — the same standard used by the district court in Walton’s case — but rather was with the district court’s failure to consider Ford’s evidence demonstrating his alleged insanity. In concurrence, Justice Powell agreed, stating:
[Ford’s] claim of insanity plainly fits within [Florida’s statutory] standard. According to [Ford’s] proffered psychiatric examination, [Ford] does not know that he is to be executed, but rather believes that the death penalty has been invalidated. If this assessment is correct, [Ford] cannot connect his execution to the crime for which he was convicted. Thus, the question is whether [Ford’s] evidence entitles him to a hearing in Federal District Court on his claim.
Id. at 422-23, 106 S.Ct. 2595 (emphasis added) (internal citations omitted).
In this case, it is clear that the district court provided Walton all the process he was due under Ford. Whereas in Ford the petitioner was provided no hearing and the governor and- the district court failed to consider Ford’s evidence demonstrating his alleged incompetence, the distxict court in this case heard all the evidence presented by Walton and Virginia. The district court went even further and appointed another expert' — one endorsed by Walton — to provide yet another assessment of Walton’s mental state. There is no question that the district court diligently protected the right of Walton to explore fully the issue of his competence to be executed.8
[170]*170Walton, however, argues that the district court erred by not following the substantive test in Ford for determining whether a condemned inmate is competent to be executed. In particular, Walton argues that an inmate is competent to be executed only if he is able to: (1) comprehend that he is to be executed as punishment for his crime; (2) assist his counsel during the competency proceeding; and (3) prepare for his death in some meaningful manner.9
The first component of Walton’s proposed competency test is that a condemned inmate must be able to comprehend that he is sentenced to death and the reason why. Virginia asserts that this narrow inquiry constitutes the proper legal test to determine competency for execution, and we agree. Although the Ford plurality did not specifically set out to create a Constitutional definition for mental incompetence, the plurality did give several rationales for its primary holding that the Eighth Amendment prohibits the execution of the insane. One of its rationales is that the retributive value of executing a condemned inmate is thwarted if he “has no comprehension of why he has been singled out and stripped of his fundamental right to life.” Id. at 409, 106 S.Ct. 2595. The plurality further stated that 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.” Id. at 417, 106 S.Ct. 2595. Justice Powell implicitly adopted this particular rationale in his concurrence when he proposed his test for determining competency: “I would hold that the Eighth Amendment forbids the execution only of those who are unaware of the punishment they are about to suffer and why they are to suffer it.” Id. at 422, 106 S.Ct. 2595. Justice Powell’s proffered test represents the only ground on which a majority of the Court agreed regarding the standard for determining mental competence to be executed, and we are bound by it. See Gregg v. Georgia, 428 U.S. 153, 169 n. 15, 96 S.Ct. 2909, 49 L.Ed.2d 859 (1976) (stating that when there are multiple rationales given by different justices to support one judgment “the holding of the Court may be viewed as that position taken by those Members who concurred in the judgments on the narrowest grounds”).10
[171]*171Justice Powell’s two-part test to determine competency to be executed has been widely recognized or adopted as the appropriate test for determining mental competence to be executed. The Supreme Court has cited Justice Powell’s test with approval, see Penry v. Lynaugh, 492 U.S. 302, 333, 109 S.Ct. 2934, 106 L.Ed.2d 256 (1989), overruled on other grounds by Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002), and Congress followed Justice Powell’s test in enacting its statutory test for determining competency, see 18 U.S.C. § 3596(c) (“A sentence of death shall not be carried out upon a person who, as a result of mental disability, lacks the mental capacity to understand the death penalty and why it was imposed on that person”). In addition, all four federal circuit courts that have addressed competency to be executed have recognized Justice Powell’s proffered test as the appropriate standard by which to determine competence. See, e.g., Scott v. Mitchell, 250 F.3d 1011, 1014 (6th Cir. 2001) (concluding that the standard established in “Ohio’s Ford statute,” ie., “that the convict in question does not have the mental capacity to understand the nature of the death penalty and why it was imposed upon the convict,” appropriately defines incompetence to be executed); Massie v. Woodford, 244 F.3d 1192, 1195 n. 1 (9th Cir.2001) (citing Ford for the proposition that “the Eighth Amendment forbids the execution only of those who are unaware of the punishment they are about to suffer and why they are to suffer it”); Fearance v. Scott, 56 F.3d 633, 640 (5th Cir.1995) (recognizing that the Ford standard requires only that an inmate “know the fact of his impending execution and the reason for it”); Rector v. Clark, 923 F.2d 570, 572 (8th Cir.1991) (stating that “according to Ford, we must examine two factors in assessing petitioner’s competency to be executed: (1) whether petitioner understands that he is to be punished by execution; and (2) whether petitioner understands why he is being punished”). Moreover, most states that have a statutory definition of competency for execution use Justice Powell’s two-part test.11 Last, [172]*172although the dissent asserts that the district court’s findings of fact are not sufficient, it also agrees that Justice Powell’s test is the appropriate competency standard. Dissent, infra at p. 35 (“I agree that the test for competency under the Eighth Amendment is whether an individual understands that he is to be executed and why”).
Walton next argues that an inmate must be able to assist in his defense throughout the competency determination process. Walton’s counsel candidly and correctly conceded at oral argument that only four members of the Ford Court would have required that an inmate be able to assist his counsel to be deemed competent for execution. The plurality would have added this requirement based on the common-law premise that “had the prisoner been of sound memory, he might have alleged something in stay of judgment or execution.” Ford, 477 U.S. at 407, 106 S.Ct. 2595. Justice Powell found only slight merit for such a requirement because “[m]odern practice provides far more extensive review of convictions and sentences than did the common law, including not only direct appeal but ordinarily both state and federal collateral review. ... It is thus unlikely indeed that a defendant today could go to his death with knowledge of undiscovered trial error that might set him free.” Id. at 420, 106 S.Ct. 2595.
The procedural history of Walton’s numerous challenges to his sentence and conviction provides a good example of the exhaustive modern safeguards and procedures available to condemned inmates. Since 1997, Walton has pursued several rounds of direct and collateral review-— always represented by counsel — in both state and federal court to test the validity of his conviction and sentence. All of these challenges failed, and Walton, now in his second federal habeas proceeding, makes no further attack on his sentence or conviction. The only remaining issue is whether Walton is competent to be executed, and we conclude that there is no Constitutional requirement12 under Ford that Walton be able to assist counsel to be deemed competent to be executed.13
Last, Walton proposes that competency for execution requires that a condemned inmate have the capacity to prepare himself mentally and spiritually for his passing to “another world.” Walton’s Brief p. 32. We conclude that Ford mandates no such requirement. Justice Powell — who provided the fifth vote in Ford— did not require that an inmate have the capacity to prepare mentally and spiritually for his passing in his two-part test. To the contrary, Justice Powell clearly stated that “I would hold that the Eighth Amendment forbids the exe-cution only of those who are unaware of the punishment they are about to suffer and why they are to [173]*173suffer it.” Ford, 477 U.S. at 422, 106 S.Ct. 2695 (emphasis added).14 Therefore, we conclude that the Eighth Amendment does not require that an inmate have the capacity to prepare for his passing to be deemed competent to be executed.
In determining whether Walton is competent to be executed, the district court specifically examined whether Walton understands that he is to be punished by execution and whether he understands why he is to be punished. Walton, 306 F.Supp.2d at 601. Because the district court faithfully followed Justice Powell’s two-part test, we conclude that the district court employed the proper legal test in making its competency determination.
B.
Walton also argues that, even applying the Powell two-part test, the district court clearly erred in finding him competent to be executed. Walton contends that the evidence overwhelmingly demonstrates his incompetence. We disagree.
We review factual findings by the district court under the clearly erroneous standard set forth in Federal Rule of Civil Procedure 52(a). Monroe v. Angelone, 323 F.3d 286, 299 (4th Cir.2003); Fields v. Attorney Gen. of Md., 956 F.2d 1290, 1297 n. 18 (4th Cir.1992). Our scope of review is narrow; we do not exercise de novo review of fac-tual findings or substitute our version of the facts for that found by the district court. Jiminez v. Mary Washington College, 57 F.3d 369, 378 (4th Cir.1995).15 Instead, “[i]f the district court’s account of the evidence is plausible in light of the record viewed in its entirety, the court of appeals may not reverse it even though convinced that had it been sitting as the trier of fact, it would have weighed the evidence differently.” Anderson v. City of Bessemer City, 470 U.S. 564, 573-74, 105 S.Ct. 1504, 84 L.Ed.2d 518 (1985). Thus, facts found by the district court are conclusive on appeal “unless they are plainly wrong.” Jiminez, 57 F.3d at 378-79. A factual finding by the district court may be reversed only if, “although there is evidence to support it, [174]*174the reviewing court on the entire evidence is left with the definite and firm conviction that a mistake has been committed.” United States v. United States Gypsum Co., 333 U.S. 364, 395, 68 S.Ct. 525, 92 L.Ed. 746 (1948).
The parties presented vastly conflicting evidence whether Walton understands that his execution will result in his death. After considering all of the evidence submitted by the parties, the district court sought yet another professional opinion by appointing a neutral expert, Dr. Mills, who Walton strongly endorsed as an objective expert. When Dr. Mills met with Walton, Walton was able to volunteer that he was going to be executed for killing three people and that his execution would be “an end” or “the end.” J.A. 899. When Dr. Mills asked Walton about his religious views and his understanding of death, Walton said that he believes that he will go to heaven and then come back in some form and be able to see his family. Dr. Mills believes Walton has a very firm and clear belief in an “afterlife,” but that Walton would prefer to live in prison for the rest of his life rather than be killed. J.A. 925. In sum, Dr. Mills, who is personally opposed to the death penalty and would have preferred to find Walton incompetent, stated that he clearly believes that Walton understands that he is in prison for killing three people and that he will be executed as punishment for these crimes.
Other evidence presented by Virginia confirms Dr. Mills’ ultimate opinion that Walton is competent to be executed. For instance, Virginia presented the testimony of Dr. Arikian, á psychiatrist who has assessed hundreds of prisoners during his career and who saw Walton several times more than any of the other experts who testified. Dr. Arikian stated that he believes that Walton understands that he is going to be executed for his crimes. When confronted with the opposing view of Dr. Pandurangi, who admittedly has had very little experience with prisoners, Dr. Ariki-an replied: “I think we’re at opposite ends of the spectrum on that.... I think far from not having an understanding of what’s going on, I think [Walton] has a full understanding of what’s going on.” J.A. 579.
After reviewing the evidence in its entirety and the district court’s findings of fact, we are far from being left with the “definite and firm conviction that a mistake has been committed.” United States Gypsum Co., 333 U.S. at 395, 68 S.Ct. 525. To the contrary, the district court considered the divergent evidence presented by both sides and the neutral testimony of Dr. Mills,16 and there is substantial evidence in the record to support the district court’s finding that “Walton understands that he is in prison and has received an execution sentence for murdering three individuals [and that] Walton understands that to be executed means he will die.” Walton, 306 F.Supp.2d at 600.
[175]*175Even though the district court— after thoroughly considering the evidence — specifically found that Walton understands that he will die as punishment for his crimes, the dissent insists that the Ford test requires more. In particular, the dissent would create a new “requirement” that the district court must also specifically determine whether the condemned inmate “understand^] that to be executed means to have one’s physical life ended.” Dissent, infra at p. 186. In an attempt to add legitimacy to this new “requirement,” the dissent asserts that other courts have required “precisely” such a specific finding. Id. at 185-186. Contrary to the dissent’s contention, none of the cases it cites (or any case that we have found) supports the dissent’s new “requirement” that a court determining competency for execution must specifically decide whether the condemned inmate understands that to be “executed means to have one’s physical life ended.”17 Instead, these cases stand for the unremarkable proposition, which we have adopted, that the condemned inmate must understand that he will die as punishment for his crimes.18 In this case, the district court, faced with vastly conflicting evidence, found by a preponderance of the evidence that “Walton understands that he is sentenced to die by execution” for his crimes and, even more precisely, that Walton “understands that to be executed means that he will die.” Walton, 306 F.Supp.2d at 600-01 (emphasis added). Ford does not require more.
[176]*176In asserting that Walton may not understand that his execution will end his physical life, the dissent points primarily to the comments that Walton has made about being able to “come back to life after execution.” Dissent, infra at p. 189. While many of Walton’s beliefs about the “afterlife” might strike others as odd or unrealistic, they are not inconsistent with the district court’s finding that “Walton understands that to be executed means he will die.” Walton, 306 F.Supp.2d at 600.19 Moreover, some of Walton’s recent statements of what he believes will happen after his death are no more unrealistic than the statements Walton made to his psychiatrist and attorney during the state trial proceedings. During his recent interview in 2004, Walton told Dr. Mills that he believed that he would go to heaven but would return and be able to see his relatives. During the state trial proceedings in 1997, Walton stated that he would come back to life shortly after his execution and would be able to resurrect his dead relatives. A panel of this court, after considering Walton’s 1997 statement, nevertheless ruled in Walton’s first federal habeas proceeding that “we harbor no doubt that Walton was competent to appear in court and plead guilty.” Walton, 321 F.3d at 460. Because the standard for competency to plead guilty, which, similar to the standard for competency to be executed, requires that the defendant understand, among other things, the “consequences of the proceedings against him,” see, 18 U.S.C. § 4241; Godinez v. Moran, 509 U.S. 389, 396, 113 S.Ct. 2680, 125 L.Ed.2d 321 (1993), Walton’s recent comments about his “afterlife” clearly do not suggest incompetence any more than his similar comments did during his first federal ha-beas proceeding.
In sum, we conclude that the district court employed the proper legal test and its findings of fact are not “plainly wrong,” see Jiminez, 57 F.3d at 379. Thus, we affirm the district court’s judgment that Walton is competent to be executed.
III.
Walton also argues that the district court erred by dismissing his claim that he cannot be executed because he is mentally retarded as defined under Virginia law. We disagree.
In Atkins v. Virginia, the Supreme Court held that the Eighth Amendment prohibits the execution of the mentally retarded, concluding that “death is not a suitable punishment for a mentally retarded criminal.” 536 U.S. at 321, 122 S.Ct. 2242. The Court, however, left to the states the task of developing appropriate procedures to determine whether an inmate who claims to be mentally retarded is in fact mentally retarded. Id. at 317, 122 S.Ct. 2242. Virginia responded by enacting its statutory definition of mental retardation that requires, among other elements, that the condemned inmate’s disability originate before the age of 18 and be characterized by “significantly subaver-age intellectual functioning as demonstrated by performance on a standardized measure of intellectual functioning administered in conformity with accepted professional practice, that is at least two standard deviations below the mean.” VA. CODE ANN. § 19.2-264.3:1.1(A)(I). The Virginia Supreme Court, consistent with the standards of the American Psychiatric Association, has determined that this standardized measure corresponds to an IQ score of 70 or less. Johnson v. Commonwealth, 267 Va. 53, 591 S.E.2d 47, [177]*17759 (2004), vacated on other grounds, 544 U.S. 901, 125 S.Ct. 1589, 161 L.Ed.2d 270 (2005); see also, Walker v. True, 399 F.3d 315, 322 (4th Cir.2005) (“On a properly normed IQ test only scores of 70 or lower are two standard deviations below the mean”). Thus, Walton can be deemed mentally retarded under Virginia law only if he establishes, among other requirements, that his intellectual functioning would have corresponded to an IQ score of 70 or less before he turned 18. See Walker, 399 F.3d at 320.20
The district court dismissed Walton’s mental retardation claim, concluding that “Walton has not satisfied the statutory definition of mental retardation under Virginia law.” Walton, 269 F.Supp.2d at 700-01. Because the district court disposed of Walton’s mental retardation claim by granting the state’s motion to dismiss, our review is de novo. Walker, 399 F.3d at 319. In determining whether Walton has properly stated a claim for relief in his petition, we must decide whether Walton “has set forth facts that, if true, would demonstrate that he is mentally retarded under Virginia law.” Id. at 320.
A review of Walton’s habeas petition reveals that he fails to allege facts demonstrating that he is mentally retarded under Virginia law.21 Walton alleges that he scored 90 on an IQ test in 1996, shortly before he turned 18. Although Walton claims that “[IJittle is known” about how this testing was conducted and whether it can be considered reliable, he does not allege that this testing somehow tends to prove that he is mentally retarded, i.e, that his score on this test was actually 70 or less. Walton also alleges that he received an IQ score of 77 when his trial expert tested him a few months after he turned 18. Walton contends, however, that this score of 77 should be reduced to a score of 74 because of the “Flynn Effect.”22 Accepting these allegations in Walton’s habe-as petition as true, Walton still does not state a claim that he is mentally retarded because Virginia law requires that intellec[178]*178tual functioning be commensurate with a score of 70 or less before age 18.23
After Virginia filed its motion to dismiss Walton’s habeas petition, Walton alleged for the first time in a separate filing that his test score of 77 supports his claim of mental retardation once the Flynn Effect and the “standard error of measurement” is taken into account. Assuming that the district court could properly consider this post-petition representation, Walton does not explain what this “standard error of measurement” is or why it should reduce his particular score to 70 or less. Walton can only speculate that this standard measurement error (which a mental health expert can take into account to either raise or lower a given IQ test score by as much as five points, see id. at 322) actually lowered his given score of 77 enough to meet Virginia’s mental retardation standard.24 Such conclusory, speculative allegations do not preclude the district court’s dismissal of Walton’s claim. See United States v. Roane, 378 F.3d 382, 400 (4th Cir.2004) (concluding that speculative allegations in a habeas petition do not warrant granting the petitioner an evidentiary hearing to further pursue his claim); Fisher v. United States, 317 F.2d 352, 354 (4th Cir.1963) (stating that “bald assertions of insanity, unsubstantiated by a recital of credible facts, would justify dismissal without further proceedings”). Accordingly, because Walton failed to allege sufficient facts demonstrating that his intellectual functioning was 70 or less before he turned 18, the district court properly dismissed Walton’s mental retardation claim.
IV.
For the reasons stated above, we conclude that there is substantial evidence supporting the district court’s finding that Walton is not mentally incompetent, and we also determine that Walton has failed to sufficiently state a claim that he is mentally retarded under Virginia law. Therefore, we affirm the judgment of the district court.
AFFIRMED