Full opinion text
EDITH H. JONES, Chief Judge: Petitioner Elroy Chester (“Petitioner”) confessed and pled guilty to capital murder and was sentenced to death by a Texas jury. His conviction and sentence were affirmed on direct appeal. He sought post-conviction relief from the Texas courts, alleging that he is mentally retarded, and his execution will therefore be unconstitutional. The Texas trial court and Court of Criminal Appeals determined that Chester was not mentally retarded. Petitioner then applied for a writ of habeas corpus via 28 U.S.C. § 2254. The federal district court denied relief, and he now appeals. The state’s legal conclusions neither contradicted nor unreasonably applied federal law, nor were its factual conclusions unreasonable in light of the evidence presented in the state proceedings. See 28 U.S.C. § 2254(d)(1) — (2); Riddle v. Cockrell, 288 F.3d 713, 716 (5th Cir.2002). We therefore AFFIRM. BACKGROUND In 1997 and 1998, Petitioner embarked on a criminal spree too long and too gruesome to recount here in its full detail. He perpetrated at least five burglaries and five non-lethal assaults; worse, he left in his wake the victims, ranging from ten to eighty-seven years old, of at least five murders and three rapes. Petitioner’s career as a serial murderer and rapist culminated in the events of February 6, 1998, when his final victim, Willie Ryman III, discovered Petitioner raping his nieces, and Petitioner shot and killed Ryman. On that evening, Erin DeLeon was at home alone with her small child. After cutting the telephone wires and tampering with the security light between the garage and house, Petitioner entered the house through the unlocked kitchen door, wearing a ski-mask and gloves. With a gun to the back of Erin’s head and her ponytail in his hand, he led her from room to room to retrieve valuables. He then brought her to the living room and ordered her to turn off the lights and draw the blinds. When Claire DeLeon, Erin’s sister, returned to the home with her boyfriend Tim, Petitioner demanded their money and jewelry, then ordered them into the bathroom. Alone again with Erin, he forced her to undress, then blindfolded her with duct tape. He then ordered Tim to return, forced him to strip as well, and restrained him with duct tape. Finally he ordered Claire to enter and strip and blindfolded her with duct tape. He raped Erin and forced other sex acts, holding a gun against her head and threatening to “blow her head off’ if she resisted. He repeated this threat when he forced Clame to perform sex acts. Willie Ryman III, the DeLeon sisters’ uncle, arrived at this scene with his girlfriend Marcia Sharp, who stayed in the car while Ryman approached the house. Petitioner went to the back door and murdered Ryman with a single shot. He then approached the car, where he began shooting at its locked doors. He fired two more shots into the car before fleeing the scene. Chester was quickly implicated and captured. He confessed to Ryman’s murder and led police to the murder weapon. Although he lied to the police about where it was hidden, and about the fact that it was loaded, apparently trying to mount a violent escape, he did not succeed. He also confessed to a host of other horrific crimes. After pleading guilty to capital murder, he was sentenced to death by a Texas jury. His conviction and sentence were affirmed on direct appeal. Chester sought post-conviction relief at the state and federal levels on the grounds that he could not be executed because he is mentally retarded. Relying on the United States Supreme Court’s opinion in Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002) (holding that the execution of the mentally retarded violates the Eighth Amendment), and on the factors set forth in Ex Parte Briseno, 135 S.W.3d 1, 5 (Tex.Crim.App.2004) (implementing Atkins), the use of which our court has repeatedly blessed, the Texas trial court and Texas Court of Criminal Appeals (“TCCA”) determined that Chester was not mentally retarded. Ex parte Chester, 2007 WL 602607 (Tex.Cr.App. 2007) (unpublished) (“Chester I”). The TCCA’s detailed and thorough opinion concluded that Chester met two of the three necessary requirements for a finding of mental retardation — significant limitations in intellectual functioning and deficiencies that appeared early in life— but that he did not show “significant deficits in adaptive behavior.” Id. at *3-*4. It cited Briseno for the proposition “that courts should use the definitions of mental retardation as stated by the American Association of Mental Retardation” and for a suggested series of questions which would assist in determining the existence of deficits in adaptive behavior. Id. at *1. It acknowledged that these suggested questions were “intended only to be guidelines for the trial courts” to help them make the mental retardation determination required by Atkins “until the Legislature was to ... establish conclusively both the substantive laws and the procedures that would bring our codes into compliance with the mandate issued by Atkins.” Id. at *3. The legislature had not intervened, however, and so the Briseno factors remained the only legal guidance for lower Texas courts in applying the AAMR definition and determining the presence or absence of “significant deficits in adaptive behavior.” Id. The TCCA concluded that the trial court’s finding that Petitioner failed to demonstrate significant deficits in adaptive behavior was supported by the evidence. The trial court had heard Petitioner’s evidence regarding his 1987 “Vineland test,” on which he achieved a Vineland Adaptive Behavioral Scales score (1CVABS”) which would typically indicate mild mental retardation. It also, however, heard evidence regarding Chester’s classification during his school years as “learning disabled” (rather than retarded), and found more credible the testimony of a diagnostician who testified that Petitioner’s school records were accurate and that a “learning disability” designation does not imply mental retardation. It also noted the planned nature of Petitioner’s crimes, both the capital crime and other crimes, in which Petitioner took a great many steps to avoid detection. It noted that he acted independently rather than as an accomplice. The trial court considered conflicting testimony regarding Petitioner’s ability to converse coherently, and found more credible the testimony of the expert who testified that Petitioner could converse coherently on a wide range of topics. It found that Petitioner could lie and hide facts to protect himself, as evidenced by his scheme to mislead investigators in order to obtain his loaded gun while in custody. The TCCA therefore affirmed the trial court’s factual finding that Petitioner failed to demonstrate significant deficits in adaptive behavior by a preponderance of the evidence. Id. at *9. Petitioner then applied for a writ of habeas corpus pursuant to 28 U.S.C. § 2254, now alleging (as he must) not only his own mental retardation and the resulting unconstitutionality of his sentence, but that the TCCA’s determination was contrary to and an unreasonable application of the holding of Atkins, and that the TCCA’s decision was based on an unreasonable finding of fact in light of the record before it. The federal district court denied relief, and he appealed. DISCUSSION I. AEDPA Review 28 U.S.C. § 2254(d) bars relitigation of any claim “adjudicated on the merits” in state court, subject only to exceptions in Section 2254(d)(1) and (d)(2). Harrington v. Richter, — U.S. -, 131 S.Ct. 770, 784, 178 L.Ed.2d 624 (2011). Section 2254(d)(1) contains two overlapping but distinct exceptions: an “unreasonable application” prong and a “contrary to” prong. See Terry Williams v. Taylor, 529 U.S. 362, 404, 120 S.Ct. 1495, 1519, 146 L.Ed.2d 389 (2000). Federal courts may not grant habeas relief pursuant to § 2254(d)(1) “unless the adjudication of the claim ... resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States.” 28 U.S.C. § 2254(d)(1). In this context, “clearly established federal law ‘refers to the holdings, as opposed to the dicta, of [the Supreme] Court’s decisions as of the time of the relevant state-court decision.’” Valdez v. Cockrell, 274 F.3d 941, 946 (5th Cir.2001) (quoting Terry Williams, 529 U.S. at 412, 120 S.Ct. at 1523). Section 2254(d)(2) excepts from the general bar on relief those cases in which the adjudication of the claim “resulted in a decision that was based on an unreasonable determination of the facts in light of the evidence presented in the State court proceeding.” 28 U.S.C. § 2254(d)(2). A reviewing federal court presumes that the state court’s factual findings are sound unless the petitioner rebuts the “presumption of correctness by clear and convincing evidence.” Miller-El v. Dretke, 545 U.S. 231, 240, 125 S.Ct. 2317, 2325, 162 L.Ed.2d 196 (2005); Maldonado v. Thaler, 625 F.3d 229, 236 (5th Cir.2010). This standard is demanding but not insatiable; deference does not by definition preclude relief. Miller-El, 545 U.S. at 240, 125 S.Ct. at 2325. As the Supreme Court has recently reminded, “If [§ 2254(d)’s] standard is difficult to meet, that is because it was meant to be.... It preserves authority to issue the writ where there is no possibility fair-minded jurists could disagree that the state court’s decision conflicts with [the Supreme] Court’s precedent. It goes no farther.” Harrington, 131 S.Ct. at 786 (emphasis added) (internal quotation marks and citation omitted). Petitioner claims that he is entitled to relief under both 28 U.S.C. § 2254(d)(1) and 28 U.S.C. § 2254(d)(2); he asserts that the state court’s adjudication resulted in a decision contrary to and involving an unreasonable application of clearly established federal law and was based on an unreasonable determination of the facts in light of the evidence presented in the State Court proceeding. We address these claims in turn. II. Section 2251(d)(1) Claims A state court’s judgment falls within the “unreasonable application” exception of § 2254(d)(1) if the state court correctly identifies the governing legal principle from the Supreme Court’s decisions, but unreasonably applies it to the facts of the particular case, Busby, 359 F.3d at 713, or where it “ ‘extends a legal principle from [Supreme Court] precedent to a new context where it should not apply or unreasonably refuses to extend that principle to a new context where it should apply.’ ” LaCaze v. Warden of La. Corr. Inst. for Women, 645 F.3d 728, 734 (5th Cir.2011) (quoting Terry Williams, 529 U.S. at 407, 413, 120 S.Ct. at 1520, 1523). A federal court cannot reverse the denial of habeas relief simply by concluding that the state court decision applied clearly established federal law erroneously; rather, the court must conclude that such application was also unreasonable. See Horn, 508 F.3d at 313. In fact, “a condition for obtaining habeas corpus from a federal court” is a showing “that the state court’s ruling on the claim being presented ... was so lacking in justification that there was an error well understood and comprehended in existing law beyond any possibility for fairminded disagreement.” Harrington, 131 S.Ct. at 786-87 (emphasis added). The first step in determining whether a state court unreasonably applied clearly established federal law is to identify the Supreme Court holding that the state court supposedly unreasonably applied. See Valdez, 274 F.3d at 946 (citation omitted). In the instant case the relevant holding is that of Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002). In Atkins, the Supreme Court held that “death is not a suitable punishment for a mentally retarded criminal.” Id. at 321, 122 S.Ct. at 2252. It based this holding on its conclusion that the Eighth Amendment’s meaning is to be drawn “from the evolving standards of decency that mark the progress of a maturing society.” Id. at 311-12, 122 S.Ct. at 2247. To determine what “evolving standards of decency” would dictate in this context, the Court turned to a consideration of “the judgment of legislatures that have addressed the suitability of imposing the death penalty on the mentally retarded[.]” Id. at 313, 122 S.Ct. at 2247. After considering these judgments, the Court stated that “a national consensus” had developed against the imposition of the death penalty on the mentally retarded. Id. at 316, 122 S.Ct. at 2249. While it found that there was a national consensus opposing the execution of the mentally retarded, the Court acknowledged that there existed disagreement “in determining which offenders are in fact retarded.” Id. at 317, 122 S.Ct. at 2250. In addition, it observed that “[n]ot all people who claim to be mentally retarded will be so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus.” Id. Rather than formulating a rule for what subset of those who claimed to be mentally retarded would be ineligible for the death penalty, the Court left to the states “ ‘the task of developing appropriate ways to enforce the constitutional restriction upon [their] execution of sentences.’ ” Id. (quoting Ford v. Wainwright, 477 U.S. 399, 405, 416-17, 106 S.Ct. 2595, 2605, 91 L.Ed.2d 335 (1986)); see, e.g., Hill v. Humphrey, 662 F.3d 1335, 1342, 1360-61 (11th Cir.2011) (en banc) (stating that the United States Supreme Court “did not provide definitive procedural or substantive guides for determining when a person” is mentally retarded and holding that the Georgia Supreme Court did not violate any “clearly established” federal law by upholding Georgia’s reasonable doubt standard for establishing mental retardation). Petitioner argues that Atkins requires state courts to apply the clinical definitions of mental retardation promulgated by the American Association on Mental Retardation (“AAMR”) and American Psychological Association (“APA”) in evaluating murderers like Petitioner for possible mental retardation. Petitioner relies in particular on footnote 22 of Atkins, which noted, in the course of recounting the perceived national consensus, that state definitions of mental retardation “generally conform ... to the clinical definitions set forth” by the AAMR and APA. Atkins, 536 U.S. at 317 n. 22, 122 S.Ct. at 2250 n. 22. This means the Texas court’s analysis unreasonably applied Atkins’ holding, Petitioner concludes, because he believes the state court analysis does not conform with the AAMR and APA definitions, under which he contends he is retarded. To evaluate his claim, we turn to the TCCA’s decision and its grounding in Ex parte Briseno, 135 S.W.3d 1 (2004). Petitioner specifically alleges that the TCCA’s reliance on the Briseno factors for determining his retardation, rather than the AAMR definition, was an unreasonable application of and contrary to Atkins. We disagree. It is impossible to conclude that the state court’s analysis here, and its reliance on the factors outlined in Briseno, resulted in a decision that was based on an unreasonable application of Atkins’s holding. Before Atkins, the Texas legislature determined that to be classified as retarded, a person must prove three facts by a preponderance of the evidence: (a) significantly subaverage general intellectual functioning (proven by showing an IQ below 70) and (b) deficits in adaptive behavior that (c) originated during the developmental period (before age 18). See Tex. Health & Safety Code § 591.003(13). This definition is almost identical to the AAMR definition of mental retardation. The Texas Court of Criminal Appeals adopted the AAMR definition of retardation for death penalty cases in Briseno. 135 S.W.3d at 8. The Briseno court recognized that the AAMR definition was designed for the purpose of providing social services, not for the purposes of determining whether a person was “so impaired as to fall within the range of mentally retarded offenders about whom there is national consensus.” It also recognized that determining deficits in adaptive behavior (the second element) was highly subjective. Id. at 8. To account for these weaknesses in definition, the Briseno court listed seven factors to flesh out the AAMR definition to determine whether the convict falls within Atkins so as to be protected against the death penalty. The court held: The adaptive behavior criteria [second element] are exceedingly subjective, and undoubtedly experts will be found to offer opinions on both sides of the issue in most cases. There are, however, some other evidentiary factors which factfinders in the criminal trial context might also focus upon in weighing evidence as indicative of mental retardation or of a personality disorder: • Did those who knew the person best during the developmental stage— his family, friends, teachers, employers, authorities — think he was mentally retarded at that time, and, if so, act in accordance with that determination? • Has the person formulated plans and carried them through or is his conduct impulsive? • Does his conduct show leadership or does it show that he is led around by others? • Is his conduct in response to external stimuli rational and appropriate, regardless of whether it is socially acceptable? • Does he respond coherently, rationally, and on point to oral or written questions or do his responses wander from subject to subject? • Can the person hide facts or lie effectively in his own or others’ interests? • Putting aside any heinousness or gruesomeness surrounding the capital offense, did the commission of that offense require forethought, planning, and complex execution of purpose? 135 S.W.3d 1, 8 (2004). The Briseno court, in other words, fashioned these evidentiary factors as a means “of developing appropriate ways to enforce the constitutional restriction” set out in Atkins. And on their face, nothing about them contradicts Atkins, as they were developed explicitly to comply with Atkins. This court has never cast doubt on this approach. To the contrary, in Clark v. Quarterman, 457 F.3d 441 (5th Cir.2006), this court held that “it is not ‘clearly established Federal law as determined by the Supreme Court of the United States’ that state court analysis of subaverage intellectual functioning must precisely track the AAMR’s recommended approach.” 457 F.3d at 445. Clark specifically rejected Petitioner’s argument that “the Texas courts must apply the approach articulated by the [AAMR], which dictates that IQ examiners account for the appropriate confidence band.” Id. If Texas need not follow AAMR procedures when determining subaverage intelligence (a relatively objective determination), then it would be senseless to think Texas must follow AAMR procedures when determining deficits in adaptive behavior (a far more subjective determination). In light of this court’s previous treatment of the Briseno factors, the Supreme Court’s broad holding in Atkins, and the irrelevance for the purposes of this inquiry of Atkins’ dicta (such as footnote 22), we conclude that the application of the Briseno factors, even in the absence of specific employment of the AAMR’s methodology for determining deficiencies in adaptive behavior, cannot be an “unreasonable application” of Atkins’ broad holding. Atkins clearly did not hold — and Petitioner does not even assert that Atkins held — that states must employ the AAMR or APA definitions of mental retardation, let alone that they must employ the same underlying clinical analysis that the AAMR and APA use to determine which patients meet each prong of those organizations’ definitions; the absence of such a holding is determinative here. This analysis also disposes of Petitioner’s overlapping argument that the state court decision was “contrary to” clearly established federal law. A state court’s decision is “contrary to” clearly established federal law if “it relies on legal rules that directly conflict with prior holdings of the Supreme Court or if it reaches a different conclusion than the Supreme Court on materially indistinguishable facts.” Busby v. Dretke, 359 F.3d 708, 713 (5th Cir.2004). For the same reasons that employment of the Briseno factors to determine adaptive functioning is not an unreasonable application of Atkins, the Briseno factors themselves do not “contradict” the Supreme Court’s holding in Atkins. See Terry Williams, 529 U.S. at 405, 120 S.Ct. at 1519 (holding state court decision is “contrary” when it “applies a rule that contradicts the governing law set forth in our cases”). This will come as no surprise, since this court has already concluded that the Briseno is not “contrary to” Atkins in precisely this regard. See Woods v. Quarterman, 493 F.3d 580, 587 n. 6 (5th Cir.2007) (“[Petitioner] also argues that Ex parte Briseno, relied on by the state habeas court, is contrary to Atkins in the way it allows courts to evaluate limitations in adaptive behavior .... We find nothing in Briseno that is inconsistent with Atkins in this regard.”). III. Section 225^(d) (2) Claims With Section 2254(d)(1) unavailable as a means for obtaining federal habeas relief, Petitioner must rely on Section 2254(d)(2), but ultimately in vain. Section 2254(d)(2) excepts from the section’s general prohibition on habeas relief cases where the adjudication of the claim in state court “resulted in a decision that was based on an unreasonable determination of the facts in light of the evidence presented in the State court proceeding.” 28 U.S.C. § 2254(d)(2). The TCCA concluded that Petitioner lacked the deficits in adaptive behavior which, combined with his subaverage intellectual ability, would have yielded the characteristics of mental retardation that render him not morally culpable of a capital crime. Petitioner, on the other hand, argues that the VABS test is dispositive: Under AAMR guidelines, a person with a VABS score of 57 and an IQ test of 69 usually would be classified as mildly mentally retarded. Petitioner argues that the Briseno factors are not adequate tools to determine whether a person is retarded, and that the TCCA’s determination was unreasonable. We must consider these claims through AEDPA’s discriminating lens, noting that “relief may not be granted unless the decision was based upon an unreasonable determination of the facts in light of the evidence presented in the State court proceedings. A factual determination made by a state court must be rebutted by clear and convincing evidence.” Clark, 457 F.3d at 443. “Factual determinations by state courts are presumed correct absent clear and convincing evidence to the contrary, § 2254(e)(1), and a decision adjudicated on the merits in a state court and based on a factual determination will not be overturned on factual grounds unless objectively unreasonable in light of the evidence presented in the state-court proceeding, § 2254(d)(2).” Miller-El v. Cockrell, 537 U.S. 322, 340, 123 S.Ct. 1029, 154 L.Ed.2d 931. As factfinder, the trial court is entitled to deference in credibility determinations. Thompson v. Keohane, 516 U.S. 99, 111, 116 S.Ct. 457, 465, 133 L.Ed.2d 383 (1995) (quoting Miller v. Fen-ton, 474 U.S. 104, 114, 106 S.Ct. 445, 452, 88 L.Ed.2d 405 (1985)). “The question of whether a defendant suffers from mental retardation involves issues of fact, and thus is subject to a presumption of correctness that must be rebutted by clear and convincing evidence under Section 2254(e)(1).” Maldonado v. Thaler, 625 F.3d 229, 236 (5th Cir.2010). Accordingly, the state courts’ factual determination is presumed correct unless Petitioner rebuts it with clear and convincing evidence. The state trial court relied on three pieces of evidence to determine that Petitioner had no significant deficits in adaptive behavior: • Expert testimony stated that Chester could communicate clearly, understood current, topical matters, and understood his current legal situation. • Chester’s criminal spree demonstrated the ability to plan, avoid detection, and lie. • Chester attempted to escape police custody by lying about the location of the hidden murder weapon so that he could grab it. Petitioner responds that the Briseno factors and the state’s evidence only focus on recent events (the crimes and recent interviews) as opposed to his full history. Petitioner presented (and represents in his petition) the following evidence: • The Vineland Adaptive Behavior Survey score of 57. Under AAMR guidelines, this indicates that Chester has deficits in adaptive behavior. • Expert testimony from Dr. Orloff. • Testimony from family members that Chester was always “stupid.” • Testimony from school personnel stating that Chester was stupid or retarded. • Evidence that Chester enrolled and participated in the Mentally Retarded Offenders Program of the Texas Department of Criminal Justice. The state trial court found, however, that Petitioner’s evidence was unpersuasive or not credible. It discounted the family and school administrator’s testimony as indicative only of a learning disability, not retardation. Further, the court found that the family had an incentive to lie. Similarly, it found that Dr. OrlofPs testimony was not credible, due to his insufficient exposure to Petitioner and to his lesser credentials. Also, Petitioner’s enrollment in the Mentally Retarded Offenders Program’was not dispositive because official policy allowed non-retarded convicts to participate. The Texas Court of Criminal Appeals, while acknowledging that test scores alone might have indicated mental retardation, nevertheless was compelled to find that the evidence supported the trial court’s finding that Petitioner is not mentally retarded. Petitioner has offered no “clear and convincing evidence” rebutting the underlying findings or the ultimate finding against mental retardation. While a different factfinder might reach a different conclusion than the state courts, this court only reviews the proceedings .to determine whether Petitioner presented clear and convincing evidence that rebuts the presumption that the state trial court’s determination was correct. § 2254(d)(2), (e)(1). Petitioner failed to do so. Proceedings at the state trial court were a battle between experts with additional testimony and evidence that was inconclusive and invited credibility testing. It is not this court’s place to second-guess the court’s credibility determinations. This analysis conclusively establishes that § 2254(d)(2) avails Petitioner nothing. But we wish to note a few striking facts from the record that highlight the deficiency of petitioner’s claim that the state courts’ factual findings regarding deficiencies in adaptive behavior were “unreasonable.” Petitioner carefully cased the house of his victims, located the telephone box, cut the telephone wires] entered through an unlocked door (presumably to avoid the noise that would accompany breaking in), disguised himself in a ski mask, and raped/sodomized the two women inside using all the precautions one might expect to see from a clever criminal. After murdering the girls’ uncle, Petitioner fired his gun into the locked doors of the victim’s car, apparently reasoning that shooting a lock would break it and cause it to fail. This was hardly the work of a person with diminished mental capacity; it was problem-solving in response to a crisis. Atkins explains: [C]linical definitions of mental retardation require not only subaverage intellectual functioning, but also significant limitations in adaptive skills such as communication, self-care, and self-direction that became manifest before age 18. Mentally retarded persons frequently know the difference between right and wrong and are competent to stand trial. Because of their impairments, however, by definition they have diminished capacities to understand and process information, to communicate, to abstract from mistakes and learn from experience, to engage in logical reasoning, to control impulses, and to understand the reactions of others. There is no evidence that they are more likely to engage in criminal conduct than others, but there is abundant evidence that they often act on impulse rather than pursuant to a premeditated plan, and that in group settings they are followers rather than leaders. 536 U.S. at 318, 122 S.Ct. at 2250 (emphasis added). It seems obvious that Petitioner did not act on an impulse, but rather “pursu[ed] a premeditated plan,” acting of his own volition rather than as a “followed ].” Id. Indeed, he masterminded a sophisticated break-in and dealt with a crisis as it developed. Nothing about this crime suggests Petitioner had difficulties “processing] information” or “engaging] in logical reasoning.” Id Of course, the Petitioner’s burden here is much higher than simply convincing us that Petitioner is not mentally retarded under Atkins. He has to show by clear and convincing evidence that the state court’s determination was unreasonable; he falls far short of this burden. CONCLUSION Because the TCCA’s decision was not contrary to or an unreasonable application of clearly established federal law, and because it was not based on an unreasonable factual determination in light of the evidence before it, we AFFIRM the district court’s denial of habeas relief. . Indeed, the Briseno factors obviously evoke Atkins's language which, in turn, evokes the AAMR findings. The first Briseno factor, regarding developmental stages, ties to the Afkins discussion of the onset of mental retardation before age 18. 536 U.S. at 318, 122 S.Ct. 2242. The second and third, regarding impulsive behavior and leadership, tie to the Atkins note that the retarded “often act on impulse rather than pursuant to a premeditated plan, and that in group settings they are followers rather than leaders.” Id. The fourth, regarding rational actions and social propriety, ties to the Atkins discussion of "understandfing] the reactions of others.” Id. The fifth, regarding focused responses to questions, evokes the Atkins discussion of “diminished capacities to understand and process information, to communicate....” Id. The sixth, concerning the ability to deceive, seems related to Atkins's mention of “capacit[y] to understand and process information, to communicate, to abstract from mistakes and learn from experience, to engage in logical reasoning.... ” Id. And the seventh, involving forethought and planning, seems tied to Atkins's mention of action "pursuant to a premeditated plan.” Id. The Briseno factors thus are not arbitrary creations of the Texas judiciary but rather carefully constructed considerations that tie directly to Atkins. . Chester’s IQ tests have resulted in varying numbers, but most of those numbers would qualify him as mentally retarded under the AAMR definition if coupled with deficits in adaptive behavior. . Petitioner and the dissent repeatedly claim that the state courts relied "solely” on the Briseno factors. The dissent uses this device to assert that the TCCA's decision is "contrary” to Atkins legally. But the TCCA opinion (a) states the proper test, (b) states how the AAMR guidelines are informed by the Briseno factors, and (c) corrects the state habeas court to confirm that Petitioner's diagnostic tests alone usually indicated a diagnosis of mild mental retardation. The court clearly took the test results into account but found them overborne by evidence and credibility determinations of the trial court. This is not "sole reliance” on improper factors but a faithful application of the principle, acknowledged in Atkins itself, that the adaptive functioning component of mental retardation is complex. The dissent would, contrary to Atkins, either prevent the state court from applying its expertise here, or confine the state “solely” to diagnostic test results in debatable cases. . Petitioner’s other crimes, hilly documented in the state court record and in the TCCA's opinion, further illustrate his cunning criminal calculations. As an example, the murder of John Sepeda — to which Petitioner confessed — similarly involved the cutting of telephone lines leading into a residence’s call box. And before murdering Cheryl DeLeon, Petitioner unscrewed the lightbulb in the outdoor security light. Evidently, Petitioner was able "to abstract from mistakes and learn from experience....” Atkins, 536 U.S. at 318, 122 S.Ct. at 2250.
DENNIS, Circuit Judge, dissenting: I respectfully dissent because the majority opinion affirms a Texas Court of Criminal Appeals (TCCA) death penalty judgment that is contrary to the federal law clearly established by Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002): When Atkins banned the execution of mentally retarded offenders, it defined mental retardation as generally conforming to the three-part clinical definitions set forth by the American Association on Mental Retardation (AAMR) and the American Psychiatric Association (APA), which were quoted by the Court in Atkins. In the present case, the TCCA, instead of applying the “adaptive skill areas” part of that definition, id. at 308 n. 3, 122 S.Ct. 2242, applied its own substantively contrary state law, known as the “Briseno factors,” in erroneously deciding that Elroy Chester failed to prove that he is mentally retarded. For this reason, I would vacate the federal district court’s judgment affirming the TCCA’s judgment and remand the case to the federal district court for further proceedings applying the entire correct clinical definition of mental retardation as required by Atkins. In Atkins, the Supreme Court held that the Eighth Amendment’s prohibition of “cruel and unusual punishments” bars the execution of mentally retarded offenders. The Court reasoned that: (1) there is a national consensus among state legislatures and Congress that the execution of mentally retarded offenders is excessive punishment, id. at 314-16, 122 S.Ct. 2242; (2) the statutory definitions of “mental retardation” used by states in that national consensus are not identical, but generally conform to, the clinical definitions of “mental retardation” set forth by the AAMR and APA, id. at 317 n. 22, 122 S.Ct. 2242; and (3) the Supreme Court’s independent evaluation of the issue revealed no reason for the Court to disagree with the national legislative consensus, id. at 321, 122 S.Ct. 2242. Based on this rationale, the Atkins Court concluded that the Eighth Amendment “ ‘places a substantive restriction on the State’s power to take the life’ of a mentally retarded offender,” id. (quoting Ford v. Wainwright, 477 U.S. 399, 405, 106 S.Ct. 2595, 91 L.Ed.2d 335 (1986)), and that this constitutional restriction protects individuals who “fall within the range of mentally retarded offenders about whom there is a national consensus,” id. at 317, 122 S.Ct. 2242. Further, Atkins made plain that the AAMR and APA “clinical definitions of mental retardation require not only subaverage intellectual functioning, but also significant limitations in adaptive skills such as communication, self-care, and self-direction that became manifest before age 18.” Id. at 318, 122 S.Ct. 2242. Thus, in deciding whether a person is mentally retarded and therefore exempt from execution under the Eighth Amendment, a state court must apply each of the three prongs — subaverage intellectual functioning; adaptive functioning limitations; and onset prior to age eighteen — of a definition that generally conforms to the AAMR and APA clinical definitions of “mental retardation.” In Atkins, the Court also concluded that “[n]ot all people who claim to be mentally retarded will be so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus. As was our approach in Ford v. Wainwright with regard to insanity, “we leave to the State[s] the task of developing appropriate ways to enforce the constitutional restriction upon [their] execution of sentences.’” Id. at 317, 122 S.Ct. 2242 (alterations in original) (citation omitted) (quoting Ford, 477 U.S. at 416-17, 106 S.Ct. 2595). In so doing, the Ford Court made clear that when “the Eighth Amendment bars execution of a category of defendants defined by their mental state[,] [t]he bounds of that category are necessarily governed by federal constitutional law.” Ford, 477 U.S. at 419, 106 S.Ct. 2595 (Powell, J., concurring in part and concurring in the judgment, but speaking for the majority on this point). Thus, by closely following Ford, Atkins signals clearly that federal constitutional law governs the bounds of the category of mentally retarded individuals who are exempt from execution, although the states, within the confines of due process, may devise procedures to govern mental retardation determinations. Our en banc court and panels have adopted this understanding of Atkins. See Moore v. Quarterman, 533 F.3d 338, 341 (5th Cir.2008) (en banc) (“Atkins specifically reserved to the states the adoption of procedures to implement its new constitutional rule....” (emphasis added)); Wiley v. Epps, 625 F.3d 199, 207 (5th Cir.2010) (“[E]ven though Atkins left to the states the job of implementing procedures for determining who is mentally retarded, ‘it was decided against the backdrop of the Supreme Court’s and lower court’s due process jurisprudence.’ ” (emphasis added) (quoting Rivera v. Quarterman, 505 F.3d 349, 358 (5th Cir.2007))). Accordingly, the states retain substantial discretion to create appropriate procedures, but they may not substantively redefine mental retardation so as to permit the execution of those who “fall within the range of mentally retarded offenders about whom there is a national consensus.” Atkins, 536 U.S. at 317, 122 S.Ct. 2242. In Atkins, the Supreme Court quoted and referred to the AAMR definition of mental retardation as follows: “Mental retardation refers to substantial limitations in present functioning. It is characterized by [ (1) ] significantly subaverage intellectual functioning, [ (2) ] existing concurrently with related limitations in two or more of the following applicable adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work[; and (3) ] Mental retardation manifests before age 18.” 536 U.S. at 309, 122 S.Ct. 2242. The Texas habeas trial court, in considering Chester’s habeas petition, did not apply the second element of the AAMR definition to determine if Chester had “related limitations in two or more of the following applicable adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work.” Instead, the trial court applied the “Briseno factors,” a series of questions originally suggested by the TCCA in Ex parte Briseno, 135 S.W.3d 1 (Tex.Crim.App.2004), which the TCCA itself has described as being “non-diagnostic criteria.” Ex parte Van Alstyne, 239 S.W.3d 815, 820 (Tex.Crim.App.2007). Although the factors were initially conceived of as “evidentiary factors which factfinders ... might also focus upon in weighing evidence as indicative of mental retardation or of a personality disorder,” Briseno, 135 S.W.3d at 8, the TCCA in the present case used the Briseno factors as a substantive part of its mental retardation definition, instead of the second prong of the AAMR definition (the AAMR clinical adaptive skills criteria) to determine that Chester had not proved he had adaptive skills deficits, and, therefore, that Chester failed to prove he is mentally retarded. See Ex parte Chester, No. AP-75037, 2007 WL 602607 (Tex.Crim.App. Feb. 28, 2007) (unpublished). Chester introduced evidence that he scored under 70 in 4 of the 5 full-scale IQ tests that he has taken since the age of seven years, and scored 57 on the Vineland Adaptive Behavior Survey (VABS), a clinical adaptive functioning test. His evidence showed he has been unable to live or work independently, and his experts and lay witnesses related that he suffered from mild mental retardation and was deficient in several adaptive behavioral areas. The state habeas trial court, which gave no reason for applying the Briseno factors to the exclusion of the AAMR adaptive skills criteria and the VABS test results, found that Chester failed to disprove any of the Briseno factors, was therefore not limited in adaptive functioning, and thus not mentally retarded for this reason alone. See Chester, 2007 WL 602607, at *4. The TCCA affirmed, approving of the trial court’s use of the Briseno factors to the exclusion of clinical adaptive skills criteria to define mental retardation. Id. at *9. The U.S. District Court denied federal habeas relief, on the ground that Chester’s application failed under the seventh Briseno factor alone. Chester v. Quarterman, No. 5:05cv29, 2008 WL 1924245, at *7 (E.D.Tex. Apr. 29, 2008) (unpublished). The TCCA’s decision was contrary to the federal law that was clearly established by the Supreme Court in Atkins. Under Atkins, state courts must apply a mental retardation definition that generally conforms to all three parts of the clinical AAMR or APA definitions. The TCCA’s unique nondiagnostic Briseno factors are more constricted than, unrelated to, and substantively contrary to the adaptive deficits criteria identified in the second prongs of the AAMR and APA clinical definitions of mental retardation. Exclusively applying the Briseno factors to assess the substantive adaptive skills prong of the mental retardation definition inevitably leads to anomalous and unreliable results, including the execution of offenders who should be classified as mentally retarded and shielded from execution under Atkins and the comprehensive clinical definitions quoted therein. In other words, by affirming the Texas courts’ erroneous use of the Briseno factors in place of the adaptive skills prong of the substantive three-part rule defining mental retardation, the majority allows those state courts to circumvent the constitutional rule of Atkins and to use their more constricted definition of mental retardation to exclude substantial numbers of mentally retarded offenders from protection from execution under the Eighth Amendment. Because the decisions of the TCCA and the federal district court are based on the same error of clear constitutional law, the judgment of the federal district court should be set aside and the case should be remanded to it for further proceedings generally conforming to the clinical definitions of mental retardation as required by Atkins. I. The petitioner, Elroy Chester, robbed and raped two young women at gunpoint in their home. When the women’s uncle unexpectedly arrived at the house, Chester shot and killed him. He pleaded guilty to the crime of capital murder and was sentenced to death by a Texas jury in 1998. His conviction and sentence were affirmed on direct appeal. Chester then sought post-conviction relief at the state and federal levels on the grounds that he could not be executed because he is mentally retarded. Chester’s federal habeas petition was pending in 2002 when the Supreme Court held in Atkins that the Eighth Amendment forbids the execution of mentally retarded offenders. Consequently, Chester’s petition was dismissed without prejudice to allow him to renew his claim for state post-conviction relief on the basis of Atkins. Chester v. Cockrell, 62 Fed.Appx. 556 (5th Cir.2003). The TCCA granted Chester leave to file a successive state habeas petition and remanded his case to the state trial court for further proceedings. The trial court held an evidentiary hearing on the Atkins claim. In order to prove that he was mentally retarded, under Atkins, 536 U.S. 304, 122 S.Ct. 2242, and Briseno, 135 S.W.3d l, Chester was required to show by a preponderance of the evidence that he had (1) significantly subaverage general intellectual functioning and (2) related limitations in adaptive functioning, (3) the onset of which had occurred before Chester reached age 18. Briseno, 135 S.W.3d at 7. Chester introduced substantial evidence of his mental retardation, including full-scale IQ scores of 69 at age seven, 59 at age twelve, 77 at age thirteen, 69 at age eighteen, and 66 at age twenty-nine and a score of 57 on VABS, a standardized test of adaptive functioning. The Texas Department of Criminal Justice administered one of these IQ tests — on which Chester scored a 69 — and the VABS test in 1987, when Chester was eighteen years old. The State’s own expert testified that a person with those test scores would be correctly diagnosed as mentally retarded. In addition, an expert retained by Chester testified that he was indeed mentally retarded. Chester also supplied other evidence tending to show that he suffers from limitations in adaptive functioning. He presented evidence that he was placed in special education early in schooling and admitted into the prison Mentally Retarded Offenders Program (MROP) at approximately age eighteen; achievement testing in prison placed him at third grade levels or below. Two of his sisters testified regarding his adaptive behavior deficits, including his inability to five or work independently. A special education teacher testified regarding his limited abilities at school. One expert diagnosed Chester as mentally retarded based on a review of his records, interviews with Chester, and observation of the State expert’s interview with him. Another expert classified him as mildly mentally retarded based on a review of his MROP records. Chester asserted that he demonstrated deficits regarding the broader conceptual and practical adaptive skill areas, as well as the specific skill areas of communication, work, functional academics, self-direction, and community use. The trial court, adopting the entirety of the prosecution’s proposed findings of fact and conclusions of law, concluded that Chester had failed to carry his burden of proof as to either of the first two elements of mental retardation: significantly subaverage general intellectual functioning and related limitations in adaptive functioning. The trial court found that Chester failed to prove that he had adaptive skill deficits but it did not apply the clinical AAMR criteria to make this finding. Instead, it applied the Briseno “evidentiary factors” and concluded that, under the Briseno factors, Chester was not limited in adaptive functioning and therefore failed to satisfy the adaptive functioning prong of the tripartite clinical definitions of mental retardation. He therefore was found to be not mentally retarded. If the trial court had applied the clinical adaptive functioning criteria instead, Chester’s evidence arguably would have shown he satisfied this prong as well as the other two and that he is mentally retarded. On appeal, the TCCA partly overruled the trial court’s findings and conclusions. Chester, 2007 WL 602607. The TCCA held that Chester “has met his burden in regard to demonstrating significant limitations in intellectual functioning,” id. at *3, and that “there is no dispute as to the third part of the test, that the evidence in favor of a finding of mental retardation occurred and was recorded before the applicant reached the age of eighteen,” id. at *2. Thus, the TCCA held that Chester had satisfied the first and third prongs of the definition of mental retardation. However, the TCCA denied habeas relief because it concluded that Chester had not “[s]hown [significant [deficits in [a]daptive [b]ehavior” as required by the second prong, id. at *4, and he had therefore not carried the burden of showing that he was mentally retarded. In reaching this conclusion, the TCCA did not consider the AAMR’s or APA’s clinical definitions of mental retardation, but relied exclusively on the factors that had previously been presented in Briseno as merely “some other evidentiary factors which factfinders in the criminal trial context might also focus upon in weighing evidence as indicative of mental retardation or of a personality disorder,” Briseno, 135 5.W.3d at 8. See Chester, 2007 WL 602607, at *4-5. Chester then filed another federal habeas petition. In that proceeding, the state did not dispute that the evidence of his mental deficits developed before he was eighteen years old or “that Chester suffers from significantly sub-average intellectual functioning.” Chester, 2008 WL 1924245, at *2. But the district court departed even further than the state courts from the Atkins clinical definitions of mental retardation, expressly holding that a finding as to just one of the seven Briseno factors was a sufficient basis for denying an Atkins claim: “[A]n affirmative finding as to the seventh and final Briseno evidentiary factor is sufficient by itself to uphold a denial of relief in a habeas corpus proceeding.” Id. at *7. Thus, the district court held that the TCCA’s “rejection of [Chester’s] mental retardation claim is neither inconsistent with, nor the result of an unreasonable application of, clearly established federal law,” and denied habeas relief. Id Chester now appeals from the district court’s order denying habeas relief. II. “In a habeas corpus appeal, we review the district court’s findings of fact for clear error and review its conclusions of law de novo, applying the same standard of review to the state court’s decision as the district court.” Beazley v. Johnson, 242 F.3d 248, 255 (5th Cir.2001) (quoting Thompson v. Cain, 161 F.3d 802, 805 (5th Cir.1998)) (internal quotation marks omitted). I conclude that Chester has shown that his habeas petition should be granted under the “contrary to” clause of AEDPA, 28 U.S.C. § 2254(d)(1). Therefore, I need not consider whether he also satisfies the “unreasonable application” clause of AED-PA, 28 U.S.C. § 2254(d)(1), and need not review the district court’s findings of fact for clear error. “Under the Antiterrorism and Effective Death Penalty Act (AEDPA), a federal court may not grant § 2254 habeas relief on any ground previously disposed of on the merits by a state court unless the state decision ‘was contrary to, or involved an unreasonable application of, clearly established [fjederal law, as determined by the Supreme Court of the United States,’ or ‘was based on an unreasonable determination of the facts in light of the evidence presented in the [s]tate court proceeding.’ ” Geiger v. Cain, 540 F.3d 303, 306-07 (5th Cir.2008) (alterations in original) (quoting 28 U.S.C. § 2254(d)(l)-(2)); see also Woods v. Quarterman, 493 F.3d 580, 584 (5th Cir.2007). “A state court decision is contrary to clearly established federal law if it ‘applies a rule that contradicts the governing law set forth in [Supreme Court] cases,’ or if the state court confronts a set of facts that are materially indistinguishable from a decision of [the Supreme Court] and nevertheless arrives at a result different from [the Court’s] precedent.’ A state court decision involves an unreasonable application of clearly established federal law if the state court ‘correctly identifies the governing legal rule but applies it unreasonably to the facts of a particular prisoner’s case....’” Williams v. Quarterman, 551 F.3d 352, 358 (5th Cir.2008) (alterations in original) (citations omitted) (quoting Williams v. Taylor, 529 U.S. 362, 405-08, 120 S.Ct. 1495, 146 L.Ed.2d 389 (2000)). III. In Atkins, the Supreme Court early in its opinion set forth in full the generally accepted clinical definitions of mental retardation: The American Association on Mental Retardation (AAMR) defines mental retardation as follows: “Mental retardation refers to substantial limitations in present functioning. It is characterized by significantly subaverage intellectual functioning, existing concurrently with related limitations in two or more of the following applicable adaptive skill areas: communication, self-care, home living, social skills, community use, self-direction, health and safety, functional academics, leisure, and work. Mental retardation manifests before age 18.” Mental Retardation: Definition, Classification, and Systems of Supports 5 (9th ed.1992). The American Psychiatric Association’s [ (APA) ] definition is similar: “The essential feature of Mental Retardation is significantly subaverage general intellectual functioning (Criterion A) that is accompanied by significant limitations in adaptive functioning in at least two of the following skill areas: communication, self-care, home living, social/interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety (Criterion B). The onset must occur before age 18 years (Criterion C). Mental Retardation has many different etiologies and may be seen as a final common pathway of various pathological processes that affect the functioning of the central nervous system.” Diagnostic and Statistical Manual of Mental Disorders 41 (4th ed.2000). “Mild” mental retardation is typically used to describe people with an IQ level of 50-55 to approximately 70. Id., at 42-43. Atkins, 536 U.S. at 308 n. 3, 122 S.Ct. 2242. The Court then surveyed developments in state and federal law that showed a growing nationwide consensus that mentally retarded defendants should not be executed. See id. at 313-16, 122 S.Ct. 2242. Beginning with a Georgia law enacted in 1988, the Court counted eighteen states, along with the federal government, which had enacted legislation prohibiting the execution of mentally retarded defendants. See id. at 313-15, 122 S.Ct. 2242. Furthermore, the Court observed that “even in those States that allow the execution of mentally retarded offenders, the practice is uncommon[:] ... only five [states] have executed offenders possessing a known IQ less than 70” since 1989. Id. at 316, 122 S.Ct. 2242. The Court therefore concluded that “a national consensus has developed against” the execution of mentally retarded defendants. Id. “To the extent there is serious disagreement about the execution of mentally retarded offenders, it is in determining which offenders are in fact retarded.... Not all people who claim to be mentally retarded will be so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus.” Id. at 317, 122 S.Ct. 2242. The Court noted that “[t]he [states’] statutory definitions of mental retardation are not identical, but generally conform to the clinical definitions” promulgated by the AAMR and the APA. Id. at 317 n. 22, 122 S.Ct. 2242. Thus, the Court’s holding that “a national consensus has developed,” id. at 316, 122 S.Ct. 2242, was based on statutes which employed “definitions of mental retardation” that “generally conform to the clinical definitions” quoted above, id. at 317 n. 22, 122 S.Ct. 2242. As an additional step in its reasoning, the Court undertook an “independent evaluation of the issue.” Id. at 321, 122 S.Ct. 2242. In this step, the Court reasoned that “by definition,” people with mental retardation have certain characteristics that make their execution cruel and unusual. Id. at 318, 122 S.Ct. 2242. These characteristics include “diminished capacities to understand and process information, to communicate, to abstract from mistakes and learn from experience, to engage in logical reasoning, to control impulses, and to understand the reactions of others.” Id. Because of these characteristics, “executing the mentally retarded will not measurably further the goal of deterrence,” id. at 320, 122 S.Ct. 2242, and “the lesser culpability of the mentally retarded offender ... does not merit that form of retribution.” Id. at 319, 122 S.Ct. 2242. Moreover, mentally retarded defendants “face a special risk of wrongful execution” because of “the possibility of false confessions, [and] the lesser ability of mentally retarded defendants to make a persuasive showing of mitigation.” Id. at 320-21, 122 S.Ct. 2242. Therefore, the Court concluded, there was “no reason to disagree with the judgment of ‘the legislatures that have recently addressed the matter’ and concluded that death is not a suitable punishment for a mentally retarded criminal.” Id. (quoting Enmund v. Florida, 458 U.S. 782, 801, 102 S.Ct. 3368, 73 L.Ed.2d 1140 (1982)). In short, the holding of Atkins is that the Eighth Amendment prohibits the execution of individuals who are “so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus.” Id. at 317, 122 S.Ct. 2242. And the Court described the parameters of that “national consensus” as “generally conforming] to the clinical definitions” of mental retardation used by the AAMR and APA. Id. at 317 & n. 22, 122 S.Ct. 2242. The Court refrained from setting forth procedures for determining whether a particular defendant is “so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus.” Id. at 317, 122 S.Ct. 2242. Rather, it declared, “we leave to the States the task of developing appropriate ways to enforce the constitutional restriction upon their execution of sentences.” Id. (quoting Ford, 477 U.S. at 405, 106 S.Ct. 2595) (brackets and internal quotation marks omitted). The Atkins Court noted that this was the same “approach” that the Court had previously followed “in Ford v. Wainwright with regard to insanity.” 536 U.S. at 317, 122 S.Ct. 2242. We have previously observed that “Ford is instructive” in Atkins cases “because of the similarity of the competency and mental retardation issues: both decisions affirmatively limit the class of persons who are death penalty eligible.” Rivera, 505 F.3d at 358. The Court’s opinions in Atkins and Ford both expressly announced “that the Constitution ‘places a substantive restriction on the State’s power to take the life’ ” of certain offenders. Atkins, 536 U.S. at 321, 122 S.Ct. 2242 (quoting Ford, 477 U.S. at 405, 106 S.Ct. 2595); see also Panetti, 551 U.S. at 957, 127 S.Ct. 2842 (same). In Ford, Justice Powell’s controlling concurring opinion explained that when “the Eighth Amendment bars execution of a category of defendants defined by their mental state[,] [t]he bounds of that category are necessarily governed by federal constitutional law.” 477 U.S. at 419, 106 S.Ct. 2595. Further, the Panetti Court explained that Ford “broadly identified]” a “substantive standard for incompetency”; applying this substantive standard, the Panetti Court “rejected] the standard followed by the Court of Appeals” as being inconsistent with Ford. 551 U.S. at 960, 127 S.Ct. 2842. Thus, it is clear under both Ford and Panetti that the definition of incompetency to be executed is a matter of federal substantive constitutional law. Because Atkins expressly adopted Ford’s approach by announcing “a substantive restriction,” 536 U.S. at 321, 122 S.Ct. 2242, while giving states procedural room to “develop[ ] appropriate ways to enforce” that restriction, id. at 317, 122 S.Ct. 2242, it follows that under Atkins, too, the substantive definition of mental retardation for Eighth Amendment purposes is a matter of federal constitutional law. Atkins identified a substantive standard for mental retardation by announcing that states may not execute offenders who are “so impaired as to fall within the range of mentally retarded offenders about whom there is a national consensus.” Atkins, 536 U.S. at 317, 122 S.Ct. 2242. The Court explained that the “national consensus” was based on state-law definitions of mental retardation that “generally conform to the clinical definitions” in the AAMR-9 and DSM-IV-TR, which the Court quoted in full in its opinion. Id. at 308 n. 3, 317 & n. 22, 122 S.Ct. 2242. Therefore, in