[3]*3
ORDER
COCHRAN, J.,
delivered the Order of the Court,
joined by KELLER, P.J., MEYERS, PRICE, WOMACK, JOHNSON, KEASLER, and HERVEY, JJ.
Applicant was convicted of capital murder and sentenced to death for the 1991 robbery-murder of Dimmitt County Sheriff Ben Murray. After the Supreme Court’s decision in Atkins v. Virginia,1 applicant filed a subsequent writ of habeas corpus application alleging that he was mentally retarded and therefore exempt from execution. Based upon applicant’s prima fa-cie showing, we remanded his writ application to the convicting court for further proceedings. The trial court conducted a lengthy evidentiary hearing and made findings of fact that applicant failed to prove, by a preponderance of the evidence, that he is mentally retarded. We agree and therefore deny relief.
I.
The evidence at applicant’s capital murder trial showed that Sheriff Ben Murray was robbed and murdered in his home during the night of January 5,1991. Sheriff Murray had been stabbed numerous times and then shot in the head. His pistol, a “Thompson” pistol, and an unknown amount of money were taken. Applicant was arrested the next day. A sample of blood taken from the sheriff’s carpet matched applicant’s blood, and a sample of blood taken from applicant’s clothing matched the sheriffs blood.
While in jail on this charge, applicant suggested an escape plan to another inmate, Ricardo Basaldua.2 Applicant, who was a jail trustee, obtained a knife and gave it to Basaldua. Applicant instructed him to tell one of the jailors that he, Basaldua, needed to wash some clothes. Then, according to applicant’s plan, once Basaldua was outside his cell, he was to grab the jailor’s keys and release applicant. Basaldua did so, but he stabbed the jailor when the jailor refused to hand over his jail and truck keys. Applicant, Basal-dua, and a third prisoner, Roy Garcia, escaped in the jailer’s truck. Applicant drove. They abandoned the truck behind a Wal-Mart in a different town, and applicant led them to a tree where he dug up the gun that he had used to kill Sheriff Murray. Applicant found food and water for the three men who then hid in the woods for three days. During this time, Roy Garcia had two epileptic seizures. Applicant told Basaldua that they needed to kill Garcia because he would only slow them down, but Basaldua said, “No.” Finally, police surrounded the escapees who hid in the grass, and applicant threw away the gun before they were recaptured. Ba-saldua then led the officers to where applicant had thrown his gun. According to Basaldua, applicant was the planner and ringleader of the escape.
After his capture, Basaldua told the police what applicant had told him about the murder of Sheriff Murray. According to Basaldua, applicant and a cohort, Alberto Gonzales, appeared at the Sheriffs home offering to sell some rings.3 Applicant and [4]*4Gonzales did not actually have any rings to sell, but they used this as a ruse to get into the Sheriffs home. Once inside, a struggle began, and they stabbed the Sheriff. Then applicant grabbed the Sheriff’s pistol and shot him. They found some money “on” or “between” the walls of the Sheriff’s home. According to Basaldua, applicant had hidden the money he stole from the Sheriffs home and promised to share it with Basaldua if he helped applicant escape from jail.
The jury convicted applicant of capital murder and, based upon their answers to the special punishment issues, the trial court sentenced him to death. We upheld that conviction and sentence in a unanimous unpublished opinion.4 Applicant filed his original habeas corpus writ application on July 31,1995. This Court denied relief based on the trial court’s findings of fact and conclusions of law on November 27,1996. Thereafter, applicant filed a writ of habeas corpus in the federal district court, but that too, was denied, and the Fifth Circuit affirmed the district court’s judgment on November 26, 2001.
Applicant filed this subsequent writ application on July 10, 2002, the date he was scheduled to be executed, alleging that he was mentally retarded and therefore his execution was constitutionally impermissible under Atkins v. Virginia. We issued a stay of execution and remanded the writ application to the convicting court to conduct an evidentiary hearing on applicant’s Atkins claim. The trial judge who had presided over applicant’s capital murder trial conducted a five-day evidentiary hearing on the question of whether applicant was mentally retarded.5 On October 7, 2003, the trial court made findings of fact and concluded that:
The Applicant, Jose Garcia Briseno, is not mentally retarded, and the State of Texas is therefore not precluded from carrying out the sentence of death in accordance with the verdict of the jury in the trial court.6
The trial court forwarded the habeas record to this Court for a final determination on whether to grant or deny relief under Atkins.
II.
This Court does not, under normal circumstances, create law. We interpret and apply the law as written by the Texas Legislature or as announced by the United States Supreme Court. In Atkins, the [5]*5Supreme Court announced that there is a national consensus that those who suffer from mental retardation should be exempt from the death penalty, but it simultaneously left to the' individual states the substantive and procedural mechanisms to implement that decision. The Texas Legislature has not yet enacted legislation to carry out the Atkins mandate. Nonetheless, this Court must now deal with a significant number of pending habeas corpus applications claiming that the death row inmate suffers from mental retardation and thus is exempt from execution.7 Recognizing that “justice delayed is justice denied” to the inmate, to the victims and their families, and to society at large, we must act during this legislative interregnum to provide the bench and bar with temporary judicial guidelines in addressing Atkins claims.8 Thus, we set out the following judicial standards for courts considering those claims under article 11.071.9
A. Defining “mental retardation” for purposes of Atkins.
As the Supreme Court had previously noted, the mentally retarded are not “all cut from the same pattern ... they range from those whose disability is not immediately evident to those who must be constantly cared for.”10 In Atkins, the Supreme Court noted that any “serious disagreement about the execution of mentally retarded offenders ... is in determining which offenders are in fact retarded.” 11 Reasoning 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,”12 the Court left “to the States the task of developing appropriate ways to enforce the constitutional restriction upon its execution of sentences.”13
The term “mental retardation” encompasses a large and diverse population suffering from some form of mental disability. The DSM-IV14 categorizes the mentally retarded into four subcategories: mildly mentally retarded, moderately mentally retarded, severely mentally retarded, and profoundly mentally retarded.15 Some 85% of those officially categorized as mentally retarded fall into the highest group, [6]*6those mildly mentally retarded,16 but “mental retardation is not necessarily a lifelong disorder.”17 The functioning level of those who are mildly mentally retarded is likely to improve with supplemental social services and assistance.18 It is thus understandable that those in the mental health profession should define mental retardation broadly to provide an adequate safety net for those who are at the margin and might well become mentally-unimpaired citizens if given additional social services support.
We, however, must define that level and degree of mental retardation at which a consensus of Texas citizens would agree that a person should be exempted from the death penalty. Most Texas citizens might agree that Steinbeck’s Lennie19 should, by virtue of his lack of reasoning ability and adaptive skills, be exempt. But, does a consensus of Texas citizens agree that all persons who might legitimately qualify for assistance under the social services definition of mental retardation be exempt from an otherwise constitutional penalty? Put another way, is there a national or Texas consensus that all of those persons whom the mental health profession might diagnose as meeting the criteria for mental retardation are automatically less morally culpable than those who just barely miss meeting those criteria? Is there, and should there be, a “mental retardation” bright-line exemption from our state’s maximum statutory punishment? As a court dealing with individual cases and litigants, we decline to answer that normative question without significantly greater assistance from the citizenry acting through its Legislature.
Although Texas does not yet have any statutory provisions to implement the Atkins decision, the 77th Legislature passed House Bill 236 in 2001, even before the Atkins decision was announced, which would have prohibited the execution of mentally retarded defendants convicted of capital murder and sentenced to death.20 That bill adopted the definition of mental retardation found in Tex. Health & Safety Code § 591.003(13): “ ‘mental retardation’ means significant subaverage general intellectual functioning that is concurrent with deficits in adaptive behavior and originates during the developmental period.”21 This bill, however, was vetoed by the Governor. The 78th Texas Legislature did not [7]*7pass a statute implementing Atkins, although several bills were introduced and considered.22
This Court has previously employed the definitions of “mental retardation” set out by the American Association on Mental Retardation (AAMR), and that contained in section 591.003(13) of the Texas Health and Safety Code.23 Under the AAMR definition, mental retardation is a disability characterized by: (1) “significantly subav-erage” general intellectual functioning;24 (2) accompanied by “related” limitations in adaptive functioning;25 (3) the onset of which occurs prior to the age of 18.26 As noted above, the definition under the Texas Health and Safety Code is similar: “ ‘mental retardation’ means significantly subaverage general intellectual functioning that is concurrent with deficits in adaptive behavior and originates during the developmental period.”27
[8]*8Some might question whether the same definition of mental retardation that is used for providing psychological assistance, social services, and financial aid is appropriate for use in criminal trials to decide whether execution of a particular person would be constitutionally excessive punishment.28 However, that definitional question29 is not before us in this case because applicant, the State, and the trial court all used the AAMR definition. Until the Texas Legislature provides an alternate statutory definition of “mental retardation” for use in capital sentencing, we will follow the AAMR or section 591.003(13) criteria in addressing Atkins mental retardation claims.
The adaptive behavior criteria 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 evidentia-ry 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 [9]*9offense, did the commission of that offense require forethought, planning, and complex execution of purpose?
Although experts may offer insightful opinions on the question of whether a particular person meets the psychological diagnostic criteria for mental retardation, the ultimate issue of whether this person is, in fact, mentally retarded for purposes of the Eighth Amendment ban on excessive punishment is one for the finder of fact, based upon all of the evidence and determinations of credibility.30
B. Atkins does not require a jury determination of mental retardation in a post-conviction proceeding.
Applicant requested that a jury be empaneled to decide the factual issue of his claim of mental retardation. The convicting court denied this request, as did we. We conclude that there is no mechanism set out in our applicable habeas statute, article 11.071, that provides for a jury trial of an issue first raised in a post-conviction habeas corpus proceeding.31
Applicant contends that he was entitled to a jury determination of mental retardation pursuant to the Supreme Court’s recent decision in Ring v. Arizona32 combined with Atkins. For the following reasons, we disagree and hold that Ring and Atkins do not require a post-conviction jury determination of applicant’s claim of mental retardation.
First, we conclude that Ring does not have retroactive effect in a post-conviction habeas corpus application.33 Even if the holding of Atkins applied retroactively and may allow a person sentenced to death under Texas law to have a claim of mental retardation first addressed under article 11.071,34 we join those courts that have held that the Supreme Court’s decision in [10]*10Ring, requiring a jury determination of every fact that increases the maximum statutory penalty, is not retroactively applicable to cases on post-conviction habeas corpus review.35
Second, even if Ring were retroactive, that case does not establish a constitutional requirement that a jury determine the question of mental retardation.36 A lack of mental retardation is not an implied element of the crime of capital murder which the State is required to prove before it may impose a sentence above the maximum statutory punishment for that crime.37 Instead, as the Supreme Court made explicit in Atkins, proof of mental retardation “exempts” one from the death penalty, the maximum statutory punishment for capital murder.38 There was certainly no indication from the Supreme Court in Atkins that the fact of mental retardation is one that a jury, rather than a judge, must make. Indeed, as one state court has noted:
the majority of states which have provided a statutory exemption from capital punishment for the mentally retarded have made the finding of mental retardation a matter for the trial judge as opposed to the jury.39
[11]*11Had the Supreme Court, in its survey of these statutes in Atkins, found them constitutionally defective, it surely would have said so. Instead, the Supreme Court explicitly left “ ‘to the States the task of developing appropriate ways to enforce the constitutional restriction upon its execution of sentences.’ ”40
Third, our state habeas statute does not provide for a jury determination of fact issues on post-conviction habeas corpus review. Instead, it requires the convicting court to address and determine all previously unresolved factual issues.41 It is within the Legislature’s prerogative to enact a statute requiring or allowing a jury determination of mental retardation on post-conviction review, but unless it does so, we must follow the Legislature’s current statutory procedures.42 Thus, we hold that, when an inmate sentenced to death files a habeas corpus application raising a cognizable Atkins claim, the factual merit of that claim should be determined by the judge of the convicting court. His findings of fact and conclusions of law shall be reviewed by this Court in accordance with article 11.071, § ll.43
[12]*12C. The defendant bears the burden of proof, by a preponderance of the evidence, to establish that he is mentally retarded.
By our count, twelve of the nineteen states with statutes prohibiting the execution of mentally retarded defendants place the burden of proof upon the defendant to show mental retardation by a preponderance of the evidence.44 Similarly, House Bill 614, though not enacted by the 78th Texas Legislature, provided that the defendant must prove the issue of mental retardation by a preponderance of the evidence. The issue of mental retardation is similar to affirmative defenses such as insanity, incompetency to stand trial, or incompetency to be executed, for which the Texas Legislature has allocated the burden of proof upon a defendant to establish by a preponderance of the evidence.45 Therefore, we adopt that allocation of the burden and standard of proof, at least in the context of determining mental retardation in the habeas corpus setting where the inmate traditionally bears the burden of proof.46
Our review of a trial court’s findings of fact and conclusions of law concerning a claim of mental retardation remains the same as it has always been on habeas corpus applications. We defer to the trial court’s factual findings underlying his recommendation when they are supported by the record.47 Thus, we afford almost total [13]*13deference to a trial judge’s determination of the historical facts supported by the record, especially when those fact findings are based on an evaluation of credibility and demeanor.48 However, if the trial court’s ruling is not supported by the record, this Court may reject the findings.49
With the above substantive and procedural standards as a guide, we turn now to a review of the evidence offered at applicant’s Atkins evidentiary hearing.
III.
As this case amply demonstrates, determining what constitutes mental retardation in a particular case varies sharply depending upon who performs the analysis and the methodology used.50 Here, for example, the primary defense expert’s background is in the treatment of mental illness and mental retardation.51 His overall position was that one had to look for the person’s adaptive deficits and limitations, putting aside his positive adaptive skills. His focus is upon socially acceptable and successful skills. The State’s expert’s background is in statistical methodology and forensic diagnosis. His overall position was that one must look to the person’s positive adaptive abilities and coping skills. His focus is upon whether the person has rational responses to external situations, not necessarily whether those responses are lawful or socially appropriate. The defense expert sees the glass half-empty, the State’s expert sees the glass half-full. Both experts relied upon the same evidence and objective data to support their conclusions, yet the defense expert diagnosed mental retardation while the State’s expert found no mental retardation but did find evidence consistent with antisocial personality disorder.52
[14]*14A. Applicant did not prove, by a preponderance of the evidence, that he has significantly subaverage general intellectual functioning.
At the Atkins evidentiary hearing, applicant’s counsel stated that there was not much dispute about applicant’s IQ level. He had been tested in June, 2002, when he was 45, by applicant’s expert and obtained a full-scale IQ score of 72. He was tested by the State’s expert approximately one year later and obtained a full-scale IQ score of 74.53 According to the DSM-IV, “significantly subaverage intellectual functioning” is defined as an IQ of about 70 or below.54 Based upon these tests and the experts’ interpretation of their significance, the trial court entered a factual finding that:
[t]he preponderance of the evidence does not show that these test scores over-state the actual intellectual functioning of Applicant; the evidence in fact showed that there are good indications that the test scores understated Applicant’s intellectual functioning.
There is ample evidence in the record that supports this factual finding and thus we adopt the trial court’s finding.
B. Applicant did not prove, by a preponderance of the evidence, that he had significant limitations in adaptive functioning.
It is in the area of adaptive behavior that applicant’s and the State’s experts widely differed in their opinions concerning the same historical facts.
The evidence showed that, until the age of nine or ten, applicant was raised by his maternal great-grandmother. According to Diana Villarreal, applicant’s cousin, his great-grandmother disciplined applicant by tying him to a bed frame and whipping him. She remembers that applicant’s great-grandmother would say, “Ask him why,” when Diana asked about the beatings, but applicant would never tell her. [15]*15As a result of this discipline, applicant would run away, often for days at a time.55 To the defense experts, this was an example of a deficit in adaptive behavior because running away shows poor decision-making; a well-adapted person would seek assistance from another family member, teacher, friend, or social services provider. To the State’s expert, this was an example of good survival skills,56 and as one of the first symptoms noted in the DSM-IV of “conduct disorder,” a precursor to “antisocial personality disorder.”
Applicant attended East Elementary School in Carrizo Springs I.S.D. According to one of applicant’s cousins, this was a school for “problem children” who disrupted the classroom, but his other cousin testified that it was a school for those who had fallen behind in their work because of illness, truancy, or migrant living.57 Applicant’s records showed that his early school work was entirely unsatisfactory, but that he improved somewhat and, after being retained in “pre-primer,” was promoted to the next grade each year thereafter.58 Both the defense and State experts agreed that applicant’s school records reasonably reflected his academic functioning abilities.
At the age of thirteen, applicant went to Peoria, Illinois, to live with his mother;59 however, from age fourteen to eighteen applicant was under the care of Illinois juvenile authorities because of repeated acts of delinquency, including five “runaway” violations, truancy, aggravated battery, and two burglaries.60 According to Illinois juvenile authorities:
Joe reports that his running away from home is not due to an unpleasant home or family life. Instead, he says he does so because it is sometimes fun to stay out all night and partly because of his dislike for school. Joe also mentioned that sometimes he does not know why he leaves home, “something just comes into my head, I run away. The next day I feel sorry.” Joe admits that he has lied many times. He says he realizes that many times he has promised people that he would behave and then would break those promises. Joe feels his parents love and care about him. Both Mr. Briseno [applicant’s step-father] and Joe [16]*16feel that there has not been enough discipline given at home, yet Joe says his step-dad has a very bad temper and has on occasion beaten him. Police reports and school records mention that Joe has run away because of fear of such beatings.61
From this evidence, the defense experts saw “impulsivity,” a trait associated with mental retardation.62 On the other hand, the State’s expert saw this impulsive behavior as consistent with conduct disorder.
According to Illinois juvenile records, applicant had “slithered” through the Texas school system. He had a “high dull normal” or “low average” intelligence,63 and, at first, functioned academically at about the fourth grade level. After four years in the juvenile facilities, he was issued an eighth grade diploma.64 His behavior and work performance was “very positive,”65 although he did not express a desire to continue his education. He wanted to be a mechanic and “pump gas.”66 Both the defense and State experts pointed to the same juvenile records showing applicant’s responses to a series of assessment questions as evidence of either poor, or good, reasoning ability.67 It is highly [17]*17significant that in none of these voluminous records is there any indication from any source that any person thought applicant might be mentally retarded.
Applicant’s records and self-reports show that he began drinking alcohol at the age of nine and started abusing other substances, including marijuana, glue, LSD, speed, and barbiturates before he was 18. Both the defense and State experts agreed that applicant’s drug use may have impaired his brain functioning as well as his academic and social skills progress.
Once he was released from the Illinois juvenile system at the age of eighteen, applicant returned to Texas. By the time he was twenty-one, he had been sentenced to the Texas Department of Criminal Justice (TDCJ) for burglarizing a jewelry store with an accomplice and stealing $10,000 worth of rings, brooches and necklaces. Before this, he had been arrested for assault with a knife, a previous burglary of a building, and car theft. He returned to TDCJ shortly after he was released on parole for burglary of a vehicle. After his second release from TDCJ, he was returned again on a forgery conviction, and then, when he “escaped” during a prison furlough, he committed aggravated assault and was sentenced to more time in prison. Applicant spent approximately ten out of the fifteen years between his release from Illinois juvenile authorities and the murder of Sheriff Murray in Texas prisons.68
To the defense experts, this criminal conduct was not inconsistent with mental retardation because these crimes “were not that hard,” and they displayed an im-pulsivity and lack of successful life skills.69 To the State’s expert, this criminal conduct was consistent with antisocial personality disorder which is typified by problems with finding and keeping a job, with marriage, with law-abiding behavior, with lying, and by reckless disregard for the safety of others. He stated that applicant’s impulsivity was antisocial behavior — striking out against other people.70
[18]*18Four TDCJ officers testified at the Atkins hearing that applicant’s behavior seemed “normal” and “appropriate” in prison. He could understand them and they could understand him. They saw him reading magazines and filling out commissary forms appropriately.71 The former Chief Deputy of Dimmit County testified that he had approximately ten different dealings with applicant and found him to be “intelligent, shrewd, and very cunning.” This witness had interrogated applicant before and noted that:
someone that’s mentally retarded ... it’s hard to carry a conversation with them sometimes because they wander a lot. [Applicant] does not wander. He can keep a conversation going and he can stay in sequence.
Applicant testified briefly at the Atkins hearing and his testimony was clear, coherent and responsive. He denied doing some of the activities that the State’s lay witnesses had said he did while he was awaiting trial on the capital murder charge twelve years earlier, such as using the local law library, cooking Mexican breakfasts for the prisoners, accompanying the jailer and keeping a written tally of the jailer’s “prisoner count.”
Based upon a lengthy recitation of the testimony at the evidentiary hearing, the trial court entered a factual finding that:
The Applicant has not shown by a preponderance of the evidence that he has such “limitations in adaptive functioning” as would meet that prong of the diagnostic criteria for mental retardation. The preponderance of the evidence showed that Applicant does not have significant limitations in adaptive functioning.
Because there is ample evidence in the record to support this factual finding and the trial court’s credibility determinations, we adopt this finding.
In sum, we conclude that, while there is expert opinion testimony in this record that would support a finding of mental retardation, there is also ample evidence, including expert and lay opinion testimony, as well as written records, to support the trial court’s finding that applicant failed to prove that he is mentally retarded. We defer to the trial court’s credibility determinations, adopt the trial court’s ultimate findings of fact, and, based on those findings and our independent review, we deny relief.
HOLCOMB, J., filed a dissenting opinion.