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 those 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 pass 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 subaverage” 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 2 Some 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.
3 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 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 *9 offense, 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
