As previously indicated, the federal government and 18 capital punishment states had pre- Atkins execution bans regarding intellectually disabled capital offenders, and 16 capital punishment states have adopted post- Atkins bans. All 34 states have adopted legislative and/or judicial intellectual dis- ability defi nitions for Atkins purposes. Most states adopted some variation of the nationally recog- nized clinical defi nitions of intellectual disability, but the level of detail of the defi nitional provisions varies considerably. The statutory ban on the execution of intellectually disabled federal offenders does not include any statutory defi nition of the term. Federal courts, however, have typically applied the three-part clinical defi nitions of the term in their consideration of federal offenders’ Atkins claims (Duvall & Morris, 2006; Tobolowsky, 2014).
Although there has been a slight evolution of the clinical description of the intellectual function- ing element of the intellectual disability defi nition, the post- Penry AAIDD and APA defi nitions have consistently included assessment of this element through IQ testing and test results at least as high as 75, including consideration of the SEM (AAIDD, 2010; APA, 2013; Tobolowsky, 2014). All 34 states with Atkins intellectual disability defi nitions include an intellectual functioning criterion. Although four states have not further defi ned this criterion, the remaining states are almost equally divided between the use of an IQ benchmark for this criterion of either 70 or 75 and below—either as a fi xed benchmark, as the measure for a rebuttable presumption, or through calculations using standard devia- tions below the IQ instrument mean. Some states expressly permit non-IQ evidence regarding this criterion. California is the only state that does not reference an IQ benchmark at all but authorizes a case-by-case determination of intellectual functioning based on all relevant evidence. On the other hand, Arkansas’ defi nition only includes a rebuttable presumption regarding this criterion based on an IQ of 65 or below (Blume, Johnson, & Seeds, 2009; Ellis, 2014; Everington, 2014; Fabian, Thompson, & Lazarus, 2011; Polloway, 2015; Tobolowsky, 2014).
As described in Hall , in addition to Florida, nine other states using an IQ of 70 benchmark could be interpreted to consider an IQ of 70—without consideration of the SEM—as an outcome determina- tive cutoff score that precluded consideration of evidence of the other prongs of intellectual disability ( Hall v. Florida , 2014). The Court’s fi nding that Florida’s use of this approach was unconstitutional would apply equally to these additional states. In addition, while some states expressly required con- sideration of the SEM prior to Hall , other states had not specifi cally addressed this issue. The Hall Court made clear that “clinical defi nitions of intellectual disability, which take into account that IQ scores represent a range, not a fi xed number, were a fundamental premise of Atkins . And those clinical defi nitions have long included the SEM” ( Hall v. Florida , 2014, p. 1999; Tobolowsky, 2014).
Another factor that could potentially impact the interpretation of IQ scores is the “Flynn effect,” addressing the increase in IQ scores over time and the need to make a downward adjustment of IQ scores if based on assessment instruments with norms that do not refl ect this increase. Although the AAIDD and APA have referenced the “Flynn effect,” most states have either not addressed or not resolved its use in Atkins proceedings (Flynn, 2006; Tobolowsky, 2014).
The clinical defi nition of the adaptive functioning criterion of intellectual disability has evolved some- what since Atkins . Prior to Atkins , both the AAIDD and the APA assessed this criterion based on limitations in 2 of 10 (or 11 for the APA) specifi c adaptive skill areas (e.g., self-care, communication, self-direction, and work), and the Court referenced this aspect of the clinical defi nitions in its Atkins opinion ( Atkins v. Virginia , 2002; Bobby v. Bies , 2009). Both of these professional organizations sub- sequently consolidated these specifi c skill areas into three broader categories (i.e., conceptual, social, and practical adaptive skills or domains), and they require assessed limitations in at least one of these adaptive skill categories (AAIDD, 2010; APA, 2013; Tobolowsky, 2014).
All 34 states with Atkins intellectual disability defi nitions include an adaptive functioning crite- rion. However, ten of these states have not legislatively or judicially defi ned this criterion. Eleven states have specifi cally adopted the clinical adaptive functioning criterion referenced in Atkins involv- ing defi cits in 2 of the 10 (or 11) specifi c skill areas, and four states have specifi cally or generally
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adopted the subsequent consolidated adaptive functioning categories. Four states adopted a more general pre- Penry clinical adaptive functioning defi nition. Five states adopted a more generalized or nonclinical defi nition of adaptive functioning or combined a pre- Atkins general clinical defi nition with a nonclinical set of criteria (Blume et al., 2009; Ellis, 2014; Everington, 2014; Fabian et al., 2011; Polloway, 2015; Tobolowsky, 2014).
In light of the importance the Hall Court attached to the intellectual disability clinical defi nitions, jurisdictions’ failure to defi ne the adaptive functioning criterion or their adoption of outdated or nonclinical defi nitions subjects them to potential challenge. Such potential challenges are refl ected in the Court’s 2016 acceptance for resolution of a claim contending that Texas has unconstitutionally “prohibit[ed] the use of current medical standards on intellectual disability, and require[ed] the use of outdated medical standards” in determining both intellectual and adaptive functioning for Atkins purposes ( Moore v. Texas , 2016; Moore v. Texas , Petition, 2015, p. i).
Contemporary clinical defi nitions of intellectual disability have consistently required that an indi- vidual’s intellectual and adaptive functioning limitations originate during the developmental period of life. At the time of Atkins , both the AAIDD and the APA quantifi ed this developmental period onset as occurring prior to 18 years of age (AAIDD, 2010; APA, 2013; Atkins v. Virginia , 2002; Bobby v. Bies , 2009). The APA has subsequently maintained the developmental period onset criterion, but has deleted the specifi c age benchmark (APA, 2013; Hall v. Florida , 2014).
Thirty-two of the 34 states with Atkins procedures include a developmental period onset crite- rion in their intellectual disability defi nitions. Twenty-fi ve of these states use the 18-years-of-age benchmark to defi ne this criterion. Three states use a 22-years-of-age benchmark. Four states do not further defi ne the developmental period onset criterion. Although intellectual disability is generally a “lifelong” condition, some states additionally require that it be established at the time of the crime and/or at the time of the Atkins proceeding (Blume et al., 2009; Ellis, 2014; Everington, 2014; Fabian et al., 2011; Polloway, 2015; Tobolowsky, 2014).
Thus, 34 of the 38 capital punishment states (as of Atkins ) have adopted some variation of the clini- cal intellectual disability defi nitions for Atkins purposes. In Hall , the Court made explicitly clear that the “clinical defi nitions of intellectual disability . . . were a fundamental premise of Atkins ” ( Hall v. Florida , 2014, p. 1999). To the extent that any of these states have not adopted and implemented a full clinical intellectual disability defi nition for Atkins purposes, they risk constitutional challenge, as in Hall ( Moore v. Texas , 2016; Polloway, 2015; Tobolowsky, 2014).
