dissenting:
I respectfully dissent from the majority’s decision to vacate the district court’s judgment granting Moore relief from the death penalty. Specifically, I do not agree that Moore failed to exhaust his state court remedies. Even if I were to agree that Moore failed to exhaust his state court remedies, I believe that he nevertheless is entitled to federal habeas review because he has shown both sufficient cause for the default and actual prejudice. Additionally, a fundamental miscarriage of justice will result if we fail to consider the merits of Moore’s Atkins claim. Finally, there was sufficient evidence to support the district court’s finding that Moore is mentally retarded. Therefore, the federal district court’s ruling granting Moore ha-beas relief should be affirmed.
1.
Exhaustion of State Remedies
The state presented three alternative arguments on appeal: (1) Moore failed to exhaust state court remedies; (2) the federal district court erred in reviewing Moore’s claim de novo; and (3) the district court’s factual findings were clearly erroneous. The majority opinion disposes of the case on the exhaustion issue, finding that, under Dowthitt v. Johnson, this case is “more accurately analyzed under the ‘exhaustion’ rubric[.]” 230 F.3d 733, 745 (5th Cir.2000).1 Because the majority finds that Moore presented material additional evidence in federal court that was not presented to the state court, the majority concludes that Moore’s Atkins claim is unexhausted, and therefore dismisses his petition. Given the circumstances of this case, however, the majority’s finding of failure to exhaust is in error.
My first point of contention is with the test created by the majority. The majority recognizes that Moore filed his subsequent state habeas petition after Atkins v. Virginia, 536 U.S. 304, 321, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002), but before the Texas Court of Criminal Appeals decided Ex Parte Briseno, 135 S.W.3d 1, 8 (Tex.Crim.App.2004), the case in which the Texas Court of Criminal Appeals adopted the definition of mental retardation to be used in Atkins cases. Nevertheless, the majority has decided that “it is fair to conclude that even for habeas petitions filed pre-Briseno, a petitioner has not adequately presented the substance of his Atkins claim to the [Texas Court of Criminal Appeals] unless he has, at the very least, (1) outlined either the AAMR criteria or the substantially equivalent § 591.003(13) definition of mental retardation and (2) either alleged why he satisfies each criterion or asserted reasons why he is currently incapable of presenting any evidence on a particular prong.” Apparently, the majority has come to this conclusion because the Texas Court of Criminal Appeals indicated in Briseno that it had “previously em*495ployed” the AAMR definition of mental retardation in cases making claims under Penry v. Lynaugh, 492 U.S. 302, 109 S.Ct. 2934, 106 L.Ed.2d 256 (1989). Though the Texas courts previously had relied on definitions of mental retardation in Penry cases, they had not yet clarified what standard would be used in Atkins cases, as they were directed to do by the Supreme Court.2 At the time Moore filed his subsequent state habeas petition, there was nothing in Texas’ Atkins jurisprudence to direct Moore on how to present evidence of mental retardation in his petition. Therefore, I disagree with the majority that it is “fair to conclude” that Moore was required to present his mental retardation evidence in the manner set forth by the AAMR or the Texas Health and Safety Code.
Despite the fact that Moore was not required to present his mental retardation evidence in accordance with definitions not yet adopted by Texas, Moore did give evidence of mental retardation such that his petition was sufficiently “detailed in fact and law” to warrant a finding of exhaustion.3 In his subsequent state habeas petition, Moore provided evidence of a low IQ, that he had been in special education, had brain damage, and that the onset of these problems was prior to age 18. To claim that he is mentally retarded, Moore had to assert: (1) significantly subaverage general intellectual functioning; (2) limitations in adaptive functioning; (3) an onset prior to age 18. Briseno, 135 S.W.3d at 8. Clearly, Moore touched on all three of the criteria for mental retardation in his subsequent state habeas petition.4 Therefore, he “presented the substance of his claim to the state court[ ]”, thus satisfying the exhaustion requirement. Vasquez v. Hillery, 474 U.S. 254, 258, 106 S.Ct. 617, 88 L.Ed.2d 598 (1986).
The majority turns to this Circuit’s recent opinion, Moreno v. Dretke, as authority to disregard that Moore’s claim of being in special education classes is evidence that he suffers from limited adaptive functioning. 450 F.3d 158 (5th Cir.2006). In Moreno, this Court declined to issue a COA on Moreno’s Atkins claim, finding no error in the district court’s decision that the state court reasonably held that Moreno did not present a prima facie Atkins claim. In his subsequent state habeas petition, Moreno presented evidence that he scored a 64 on an IQ test when he was 35 years old. He also alleged that he attended special education classes as a child, thus arguing that he suffered adaptive limitations. The Moreno panel stated that Moreno’s “only evidentiary support for [the special education] claim was the psychologist’s report reciting Moreno’s self-reported educational background. He could not identify any specific special education classes or provide documentation of those classes.” Id. at 164. The majority in this case uses this statement from Moreno to conclude that Moore’s claim that he was in special education classes is not sufficient to constitute proof of limited adaptive functioning. The majority’s conclusion is in error.
In Moreno, the Court based its decision on much more than the lack of supporting *496evidence of special education classes. The Moreno panel explained, “[m]uch of this evidence, such as Moreno’s employment history, fails to suggest adaptive limitations. Balanced against this meager evidence of adaptive limitations is the substantial evidence that Moreno possesses adaptive behavioral skills.” Id. The Moreno panel did not conclude that claiming to have been in special education classes was not enough to qualify as proof of limited adaptive functioning, but that, in Moreno’s case, the evidence to the contrary outweighed the allegations that Moreno was in special education classes because he suffered limited adaptive functioning. This is not the situation in Moore’s case, and therefore, the case before us is distinguishable from Moreno.
Since Moore adequately presented the substance of his claim in state court — that he is mentally retarded and therefore not eligible for the death penalty according to Atkins — his claim was properly exhausted and there was no bar to the district court ruling on the merits of Moore’s Atkins claim. Accordingly, any new evidence presented to the district court merely supplemented Moore’s state claim. As the'majority explains:
“We have consistently held that a petitioner fails to exhaust state remedies when he presents material additional evidentiary support to the federal court that was not presented to state court.” Anderson v. Johnson, 338 F.3d 382, 386 (5th Cir.2003). Evidence is not material for exhaustion purposes if it “supplements, but does not fundamentally alter, the claim presented to the state court.” Id. at 386-87.
To support the claim that he suffers from limited adaptive functioning, Moore offered a vast amount of evidence in federal court that was not presented to state court, including testimony from family, friends, teachers, and neighbors, as well as school records. This testimony merely supplemented Moore’s claim that he was in special education classes and suffered limited adaptive functioning. Moore is allowed to “supplement and clarify” his claims presented in state court “through expansion of the record” with evidence such as “more sophisticated statistical analyses than were presented in state courts” and “introduction of new factual materials supportive of those already in the record[.]” See Randy Hertz & James S. Liebman, Federal Habeas Corpus Practice and Procedure § 23.3c, at 1088-89 (5th ed.2005) (internal citations omitted). Because Moore’s additional evidence presented in federal court did not “fundamentally alter the legal claim” presented in state court, his claim was not unexhausted. See Vasquez, 474 U.S. at 260, 106 S.Ct. 617.
The majority attempts to distinguish this case from Morris v. Dretke, 413 F.3d 484 (5th Cir.2005), a case in which this Circuit found that, though the petitioner presented more evidence in federal court than in state court, his Atkins claim was not unexhausted. The Court came to this conclusion even though it found that Morris’ federal claim was “unquestionably in comparatively stronger evidentiary posture than it was in state court” because Morris presented an IQ score in federal district court and had not presented an IQ score in his state court habeas petition. Id. at 496 (internal citations omitted). The Morris Court found that Morris “clearly acknowledged that IQ evidence was lacking in [Morris’] particular case, but still insisted ‘[t]here is good reason to believe that [Morris is retarded] ... because of the documented history of adaptive deficits[.]’ ” Id. (citations omitted).
Apparently, the Morris Court looked to Morris’ evidence of limited adaptive func*497tioning to compensate for the lack of an IQ score. Even the majority in this case concedes the Moms Court’s point that “the AAMR’s three diagnostic criteria are interdependent.” See Id. at 497. Thus, there is no reason why, in Moore’s case, this Court could not look to the evidence of special education and brain injury to deduce that Moore had limited adaptive functioning. This is especially true since, as in Morris, there is “nothing in [the] record that shows that [Moore] ‘attempted to expedite federal review by deliberately withholding essential facts from the state courts.’ ” Id. at 496. Therefore, the outcome in Morris actually supports Moore in this case. Where, as in Moore’s situation, the substance of a petitioner’s -claim was presented in state court, and additional, supplemental evidence is presented in federal court, that petitioner has exhausted his claim in federal court, even if his federal court evidence makes his case stronger.
2.
Exceptions to the Exhaustion Rule
The failure to exhaust may be excused if the petitioner “can demonstrate cause for the defaults and actual prejudice.” Martinez v. Johnson, 255 F.3d 229, 239 (5th Cir.2001). This Circuit has recognized that “[c]ause is defined as something external to the petitioner, something that cannot fairly be attributed to him that impedes his efforts to comply with the state procedural rule. ‘Cause’ factors may include interference by officials that makes compliance with the procedural rule impracticable, a showing that the factual or legal basis for the claim was not reasonably available to counsel, and ineffective assistance of counsel [... ] on direct appeal.” Matchett v. Dretke, 380 F.3d 844, 848-49 (5th Cir.2004) (internal citations omitted). Further, prejudice is found where “the specific facts and circumstances of the proceeding in which the error occurred” have “worked to the petitioner’s actual and substantive disadvantage.” Hertz & Liebman, supra, § 26.3c, at 1346-47 (emphasis in original)(citing United States v. Frady, 456 U.S. 152, 170, 102 S.Ct. 1584, 71 L.Ed.2d 816 (1982) and United States v. Olano, 507 U.S. 725, 734-35, 736, 739-41, 113 S.Ct. 1770, 123 L.Ed.2d 508 (1993)).
Given this standard, it is evident that even if Moore’s claims are unexhausted, he satisfies the “cause and prejudice” exception to the exhaustion rule. Though Moore did not provide all of the evidence available to him in order to support his assertion that he attended special education classes as a child, nor did he express his mental retardation evidence using the AAMR categories, he did state that “[t]o date, there has been no published case from the Court of Criminal Appeals giving guidance to what constitutes retardation under Texas law.” Contrary to the majority’s position, Moore’s statement regarding the then-uncertain state of Texas law does provide an explanation of why such supporting evidence was lacking— Moore had not received guidance from Texas courts on how to present his evidence of mental retardation post-Atkins. Certainly, something external to Moore, namely that Texas had not yet decided Briseno, caused Moore’s inability to present his mental retardation evidence according to an established Texas procedure. Further, the facts and circumstances of Moore’s case demonstrate that Moore was prejudiced by this lack of guidance. The fact that Moore did not know how to set forth his mental retardation evidence such that it would be acceptable to the Texas Court of Criminal Appeals caused the state court to dismiss Moore’s subsequent state habeas petition. This is clearly an “actual and substantive disadvantage” suffered by *498Moore. As such, Moore has satisfied the “cause and prejudice” exception to the exhaustion rule.
Another exception to the exhaustion rule applies to situations where the petitioner can “demonstrate ... that failure to consider the claims will result in a fundamental miscarriage of justice.” Coleman v. Thompson, 501 U.S. 722, 750, 111 S.Ct. 2546, 115 L.Ed.2d 640 (1991). The Supreme Court has made clear that the “miscarriage of justice” exception extends to cases in which “[t]he Constitutional violation has probably resulted in the imposition of a death sentence upon one who is actually innocent of a death sentence.” Hertz & Liebman, supra, § 26.4, at 1369 (internal citations omitted); see also Dug-ger v. Adams, 489 U.S. 401, 411 n. 6, 109 S.Ct. 1211, 103 L.Ed.2d 435 (1989). This means that a petitioner can invoke the “miscarriage of justice” exception if, but for the failure to exhaust, “the petitioner would have not been eligible for the death penalty because some constitutional or state statutory prerequisite for the imposition of a death sentence could not have been satisfied.” Hertz & Liebman, supra, § 26.4, at 1369-71; see also Sawyer v. Whitley, 505 U.S. 333, 343, 345-50, 112 S.Ct. 2514, 120 L.Ed.2d 269 (1992). Moore easily satisfies this exception because, as explained in section 3 of this dissent, when allowed to look at the merits of Moore’s Atkins claim, the district court properly found that Moore is mentally retarded. Therefore, in accordance with the Supreme Court’s finding in Atkins, Moore is ineligible for the death penalty, as his execution would constitute cruel and unusual punishment in violation of the Eighth Amendment. In other words, the evidence in this case shows that any alleged failure to exhaust is excused because Moore is actually “innocent of the death penalty.”
3.
The District Court’s Finding of Mental Retardation
The majority does not reach the issue of whether the district court erred in finding that Moore is mentally retarded. It is necessary to reach this issue, however, because Moore’s Atkins claim was either exhausted in state court, or his failure to exhaust is excused. Therefore, this appeal cannot be disposed of on a finding of failure to exhaust. Accordingly, it is necessary to turn to the state’s argument that the district court’s factual findings were clearly erroneous.
The district court analyzed Moore’s ha-beas petition using the AAMR definition of mental retardation, one of the mental retardation definitions adopted by the Texas Court of Criminal Appeals in Briseno. The AAMR defines mental retardation as:
A disability characterized by significant limitations in both intellectual functioning and in adaptive behavior, as expressed in conceptual, social, and practical adaptive skills. This disability originates before age 18. Briseno, 135 S.W.3d at 8; American Association of Mental Retardation, Mental Retardation: Definition, Classification and Systems of Supports (10th Ed.2002) at 1.
Therefore, as explained earlier, to prove that he is mentally retarded, Moore had to establish: (1) significantly subaverage general intellectual functioning; (2) limitations in adaptive functioning; and (3) an onset prior to age 18. See Briseno, 135 S.W.3d at 8. The district court properly found that Moore presented sufficient evidence to warrant a finding of mental retardation.
First, Moore met his burden of showing that he suffered from subaverage general intellectual functioning. The state claims that the district court erred in finding Moore mentally retarded, because that *499finding was made in the absence of a single, valid IQ score, and instead on the sole basis of subjective, anecdotal testimony from biased family members. Moore has taken four IQ tests over his lifetime. The first was the Primary Mental Abilities Test (“PMA”) given at age 6, on which he scored a 74. He also received a 76 on the WAIS-R taken at age 24 in 1991, which was adjusted to a 72.1 to account for the Flynn effect.5 On the WAIS-III, administered in 2004, Moore scored a 66. Lastly, Moore took a TONI-2 non-verbal reasoning test and scored in the Very Poor Range. At trial, though Dr. Gary Mears, the state’s expert psychologist, did testify that he had some questions about the accuracy of the IQ scores, he also stated that he would agree with Dr. Antolin Llórente, Moore’s expert psychologist, that Moore satisfied the significantly subaverage general intellectual functioning prong of the mental retardation definition. Dr. Lló-rente testified that all of Moore’s IQ scores, including the one taken at age 6, were consistent with the WAIS-III score of 66. Dr. Llórente also testified that Moore was assessed for response bias to determine whether he was fabricating his results, and no such bias was found. Given the agreement among the experts and the concession by the state’s expert, there appears to be sufficient evidence for the district court to have determined that Moore satisfied this prong of the definition.
Secondly, to support the claim that he suffers from limited adaptive functioning, Moore offered a significant amount of evidence in federal court, including testimony from family, friends, teachers, and neighbors, as well as school records.6 Though Dr. Mears stated that Moore was not limited in adaptive functioning, he admitted that he could not effectively assess adaptive functioning without the use of adaptive functioning scales. Dr. Llórente, though, did confidently conclude that Moore suffered from adaptive deficits in every area of set forth by the DSM-IV or the AAMR. Likewise, there was sufficient evidence for the district court to conclude that the onset of Moore’s mental retardation occurred before age 18. Again, the experts agreed that this was the case. In addition to the experts, testimony was given by Moore’s family members explaining that it was common knowledge within the community that Moore was “slow” as a child. Overall, the district court listened to the opinions of experts, heard testimony from family members, and reviewed Moore’s academic records, vocational work, communication skills, health and safety, social skills, leisure, self-care, home living, use of community resources, and victimization and gullibility. Based on all of these factors, there was sufficient evidence for the district court to conclude that each prong of the definition of mental retardation was satisfied. Therefore, it was not clearly erroneous for the district court to conclude that Moore is mentally retarded.
4.
District Court’s Standard of Review
The majority also does not reach the issue of whether the district court applied an incorrect standard of review to Moore’s *500habeas petition. Again, it is necessary to reach this issue because this case cannot be disposed of on the exhaustion question alone. Considering the procedural history of this case, it is apparent that the district court employed the correct standard of review.
The state takes issue with the district court’s decision to review Moore’s claim de novo and its explanation that it was doing so because the state court’s dismissal was procedural in nature and was not an adjudication on the merits. Though the state argues that large portions of Moore’s mental retardation claim are procedurally defaulted, the state still maintains that the dismissal of Moore’s subsequent state ha-beas application may not have been independent of Atkins and, thus, may not be an absolute procedural dismissal. If this is the case, then the district court should have only reviewed the state court’s dismissal to determine whether it was “contrary to, or involved an unreasonable application of, clearly established federal law as determined by the United States Supreme Court, or resulted in a decision based on an unreasonable determination of the facts in light of the evidence presented in the state court proceeding,” as directed by AEDPA. 28 U.S.C. § 2254(d)(l)-(2).
However, Moore’s claim was not adjudicated on the merits in state court. The Texas Court of Criminal Appeals dismissed Moore’s application because it found that Moore had failed to allege specific facts in his application that would satisfy the elements of the Texas subsequent application rule. This was a pure procedural decision, and did not involve the Texas Court of Criminal Appeals hearing Moore’s evidence to determine whether he is in fact mentally retarded. When a state court does not adjudicate a claim on its merits, the federal court must determine the claim de novo. Miller v. Johnson, 200 F.3d 274, 281 n. 4 (5th Cir.2000). Therefore, AEDPA’s deferential standard of review does not apply. As such, the district court did not err in undertaking a de novo review of Moore’s Atkins claim.
Conclusion
For the reasons indicated, the district court did not err in hearing Moore’s federal habeas petition. Furthermore, the district court’s ruling granting Moore habeas relief was not in error. Because it holds otherwise, I dissent from the majority opinion.
. In footnote 8, the majority concludes that, because it was not adequately briefed, the state has waived its argument that Moore’s Atkins claim is procedurally defaulted because the state court’s dismissal was based on the requirements of Tex.Code Crim. Proc. art. 11.071 § 5(a), which was an independent and adequate state court ground. I agree with the assessment that this argument is waived.
. Atkins, 536 U.S. at 317, 122 S.Ct. 2242 (leaving to the states "the task of developing appropriate ways to enforce the constitutional restriction^]”).
. The majority opinion states that Moore’s petition "cannot be considered sufficiently 'detailed in fact and law’ to warrant a finding of exhaustion.”
.The majority does not take issue with Moore's evidence of "significantly subaverage intellectual functioning” and "onset prior to age 18.” The only problem appears to be with Moore's evidence of limited adaptive functioning.
. The Weschler Adult Intelligence Scales test (the "WAIS”) is the standard instrument in the U.S. for assessing intellectual functioning. The Flynn effect recognizes that norm IQ scores across a population have increased approximately 3 points per decade.
. There is evidence that Moore was not in special education classes, but in "corrective classes.” It appears that this distinction is inconsequential, because the point is that Moore was not able to keep up with children his age.