dissenting.
I would hold that Goodwin made a sub-missible case for mental retardation such that he is entitled to a jury trial on that issue. As the principal opinion notes, Atkins v. Virginia, 536 U.S. 304, 122 S.Ct. 2242, 153 L.Ed.2d 335 (2002), makes it unconstitutional to subject a mentally retarded individual to the death penalty.
In Johnson v. State, 102 S.W.3d 535 (Mo. banc 2003), this Court ordered a new penalty phase trial to determine whether the offender was mentally retarded and, thus, whether a sentence of death would violate the constitutional standard recognized in Atkins. Johnson controls this case and, like Johnson, Goodwin should receive a new penalty phase trial. Like Johnson, Goodwin was tried, convicted, and sentenced to death. On direct appeal, his conviction and sentence were affirmed before the Atkins decision. State v. Goodwin, 43 S.W.3d 805 (Mo. bane 2001). In both cases, trial experts opined that the offender was not mentally retarded; in both cases there was evidence that supported and refuted that opinion. In each case, the motion court heard evidence of the offender’s retardation and considered, as well, the testimony of trial experts that the offender was not retarded. This Court in Johnson held that this dispute is to be resolved in a new penalty phase trial — and not by the motion court judge — where there is a genuine dispute as to the ultimate fact of whether the offender is retarded. 102 S.W.3d at 541. Unless Goodwin waives his right to a jury trial, a jury should determine this issue. Mo. Const, art. I, sec. 18(a); sec. 565.006, RSMo 2000.
Usually a post-conviction proceeding under Rule 29.15 involves the question of whether the offender received effective assistance of counsel. Although Goodwin’s arguments are couched as attacks on the adequacy of his trial counsel, and that is how the principal opinion analyzes the issue, this is not the only way to address the issue. Rule 29.15(a) broadly encompasses a claim that a “conviction or sentence imposed violates the constitution” or a claim that “the sentence imposed was in excess of the maximum sentence authorized by law.”1 Johnson relied upon these provisions of Rule 29.15(a) in applying Atkins, rather than focusing on whether trial counsel was ineffective. Id. at 537. Even though the principal opinion rejects the challenge to the adequacy of representa*43tion, Goodwin’s motion suffices to raise the constitutionality of his sentence. Goodwin does not have to meet the ineffective assistance of counsel test to prevail on his mental retardation claim. Rather, if he can demonstrate, by a preponderance of the evidence, that he is mentally retarded, then his death sentence is unconstitutional. Id. at 540.
The question for the motion court is whether there is evidence that, if believed, would cause the finder of fact in a penalty phase trial to find that Goodwin is mentally retarded. Id. at 541. Put another way, the question is whether Goodwin can make a submissible case of mental retardation. Even though there may be significant evidence to refute that claim, as there was in Johnson, the issues of credibility are for the jury, not for the motion court. The evidence Goodwin submitted in support of his Rule 29.15 claim meets this standard.
The principal opinion asserts that Goodwin did not provide documented evidence that he was retarded before age 18. The evidence presented at the Rule 29.15 hearing shows otherwise. Although, as detailed in the principal opinion, there was ample evidence that Goodwin was not retarded, there was also enough evidence that he was retarded to make a submissi-ble case.
Goodwin’s main witness at the Rule 29.15 hearing, where the sole issue was mental retardation, was Dr. Denis Keyes, an educational psychologist. Dr. Keyes specializes in mental retardation and death penalty issues, and his research was cited by the Supreme Court in Atkins. 536 U.S. at 316 n. 20,122 S.Ct. 2242.
Goodwin presented expert testimony that he is mentally retarded, with I.Q. scores of 67-74 and low adaptive skills during childhood. A 1980 I.Q. score, when Goodwin was a teenager, was 72, within the mentally retarded range, and he scored 69 on earlier verbal portions of the test. Moreover, a kindergarten teacher apparently believed that Goodwin was retarded, and he failed third and fourth grade. Goodwin was placed in a special high school program and never received the credits required to graduate from the regular high school. Witnesses testified that Goodwin exhibited serious adaptive problems as a child. None of the experts who opined that Goodwin was not retarded conducted any adaptive functioning tests. Dr. Keyes, who was the only expert to testify that Goodwin was retarded, was also apparently the only expert to review Goodwin’s adaptive skills, an essential part of a mental retardation diagnosis.
Dr. Keyes’ professional opinion is that Goodwin is “within the mild range of mental retardation, probably smack in the middle of it [with an] I.Q. around sixty-three, sixty-five.” Although Dr. Keyes is the first professional to diagnose Goodwin with mental retardation, he believes that the other experts did not consider Goodwin’s poor adaptive skills because they were not considering a mental retardation diagnosis.
The Missouri statute, section 565.030.6, RSMo Supp.2004, does not have an I.Q. cut-off or refer to any I.Q. component in the definition of “mental retardation.” Experts, however, use various I.Q. tests as part of the assessment of mental retardation. The experts at trial agreed that, with the five-point margin of error, I.Q. scores of up to 75 could be considered within the mentally retarded range. Goodwin had verbal and total scores within this range.
As noted, Johnson, 102 S.W.3d 535, is similar and on point. In both cases, there was evidence at trial that the defendant was not mentally retarded. Johnson’s experts testified that he was in the “low average” or “dull normal” range. Id. at *44538-39. One expert, who believed Johnson was mentally retarded, was known to the defense but was not called to testify. Id. Likewise, the evidence at Goodwin’s trial was mixed; although his experts testified that he was not mentally retarded, there was some evidence that could support a finding that he was. In both cases, there was considerable contrary evidence available to the motion court, so that “reasonable minds could differ as to movant’s mental abilities.” 102 S.W.3d at 540.
The role of the motion court in a case such as this is not to make the factual determination itself, as the judge did in this case. Where there is a real dispute as to the evidence, the proper remedy is to vacate the judgment and set the matter for a new trial in the penalty phase, as this Court did in Johnson. Id. at 541. The motion court in this case perceived its job as determining whether or not Goodwin is mentally retarded. However, once the threshold of a submissible case is established, that determination is to be made in a new penalty phase trial, by a jury, unless a jury is waived.
The principal opinion credits the motion court’s determination that Dr. Keyes’ testimony “laek[ed] the necessary evidence required to support his conclusions.” The motion court rejected Dr. Keyes as an expert and as a witness. The motion court found Dr. Keyes’ testing of Goodwin to be unreliable because he is not a licensed psychologist and because he relied on adaptive skills information provided by Goodwin’s family.
The considerations that caused the motion court to reject Dr. Keyes’ testimony do not negate his status as an expert witness, nor do they make his expert testimony inadmissible. All of the factors recited by the motion court go to the weight of the testimony, not to its admissibility. Resolution of disputes in the evidence, and evaluation of the credibility of an expert witness, is for the jury, not the motion court. See, e.g., Georgescu v. K Mart Corp., 813 S.W.2d 298, 299 (Mo. banc 1991). The principal opinion recognizes that credibility is normally for the jury but here thinks that the judge found the expert so unworthy of belief that it could make an exception. Exceptions should not be made, or we run the risk of the exception becoming the rule.
The principal opinion notes that Dr. Keyes’ adaptive functioning testimony is inappropriate because it was conducted when Goodwin was over 30 years old. However, the interviews were specifically designed to elicit information about Goodwin as a child. This holding by the principal opinion amounts to a determination that a person can never be found to be retarded if the necessary adaptive testing and documentation were not done before age 18, or if documentation for some reason cannot be retrieved. This interpretation of the statute does not satisfy the constitutional standard set forth in Atkins because it could allow a mentally retarded person to be executed.
The only question for the motion court at a Rule 29.15 evidentiary hearing is whether there is, in effect, a submissible case that the movant is mentally retarded. Goodwin presents such a case, and he should receive a new penalty phase jury trial on that issue.
. Rule 29.15(a) provides: “Nature of Remedy — Rules of Civil Procedure Apply. A person convicted of a felony after trial claiming that the conviction or sentence imposed violates the constitution or laws of this state or the constitution of the United States, including claims of ineffective assistance of trial and appellate counsel, that the court imposing the sentence was without jurisdiction to do so, or that the sentence imposed was in excess of the maximum sentence authorized by law may seek relief in the sentencing court pursuant to the provisions of this Rule 29.15. This Rule 29.15 provides the exclusive procedure by which such person may seek relief in the sentencing court for the claims enumerated. The procedure to be followed for motions filed pursuant to this Rule 29.15 is governed by the rules of civil procedure insofar as applicable.”