New important Atkins SCOTUS decision on fall 2025 docket: How to evaluate and interpret multiple IQ scores in Atkins cases (Hamm[AL] v Smith)?

 This fall 2025, the Supreme Court of the United States (SCOTUS) will be hearing a case related to intelligence testing in the context of Atkins intellectual disability (ID) death penalty cases. The case is Hamm v Smith.

The question before SCOTUS is :  Whether and how courts may consider the cumulative effect of multiple IQ scores in assessing Atkins claims (in the context of diagnosis ID in death penalty cases)?

Note.  In order to save space and time, instead of writing “general intelligence” or “general intellectual functioning” every time, I use the abbreviation “IQ”.

The respondent (Joseph Smith) has five IQ test scores from comprehensive IQ tests.  He obtained two scores of 75 and 74 during the developmental period (before age 22), and three scores of 72, 78, and 74 between the ages of 28 and 46.  

This case is important for assessment professionals who conduct intelligence testing in general, and potential ID diagnostic cases (Atkins cases in particular).  I find this SCOTUS case particularly interesting given that in 2021, after the 2021 release of the latest official AAIDD manual (Intellectual disability: Definition, diagnosis, classification, and systems of supports), I published a critique where I specifically stated, as one weakness of the new AAIDD manual that “…many high-stakes ID cases often include case files that include multiple IQ scores across time or from different IQ tests. Some form of guidance, at minimum in a passing reference, to the issues of the convergence of indicators and IQ score exchangeability would have been useful. Users will need to go beyond the AAIDD manual for guidance (see Floyd et al., 2021; McGrew, 2015; and Watson, 2015)” (click here to download and read this critique).

All official petitioner and respondent legal briefs (and amicus briefs) have now been published at the SCOTUS blog as of yesterday.  The number of documents posted on the SCOTUS docket are many.  To help the reader better determine which documents are most critical (the final briefs), instead of clicking away on the various links at the SCOUTUS blog, I’ve organized the petitioner and respondent brief links below.

If you prefer to not wade through all the briefs (it is not for everyone), I would encourage practicing assessment professionals read the three respondent-related briefs.  The points made are relevant to all who conduct intellectual assessments.  As a potential conflict of interest notice, I (Dr. Kevin McGrew), together with Dr. Joel Schneider and Dr. Cecil Reynolds (as noted on page three for the APA amicus brief), were consultants to APA in the drafting of that brief.  This work was performed pro bono. I, at a minimum, suggest reading all the respondent briefs.  If time permits, I would also suggest reading the petitioner’s Alabama brief and the US Justice Department Solicitor General’s brief to better understand the petitioner and respondent positions re Hamm v Smith. 

Petitioner briefs

• The state of Alabama brief.  Alabama is the petitioner.  That is, if you want to read why the State of Alabama asked SCOTUS to hear this case, click on the link provided.
• The Alabama brief also includes a very long appendix for those who want to read the prior courts related testimony from the state and various experts. This is a very long read and is not necessary for readers who only want to understand the legal and professional issues. 
• Supporting amicus brief from the US Justice Department Solicitor General.
• Two supporting briefs from legal groups—the American Legal Foundation and the Criminal Justice Legal Foundation.
• Supporting amicus briefs from other states (Idaho et al.; Kentucky)

Respondent briefs

• Smiths respondent brief.
• Supporting amicus brief from American Psychological Association (APA), American Psychiatric Assocation (ApA), and Alabama APA.
• Supporting amicus brief from AAIDD et al.

Final comment.  Those from school psychology should make note that we three consultants involved in drafting the APA/ApA,AL-APA brief all had our original educational roots in the profession of school psychology.  Furthermore, SP professionals should note the significant number of authoritative references to publications authored by school psychologists in the respondents briefs, as well as in some of the petitioners briefs.  I’ve been doing expert consultation, writing declarations, and testifying in court re: Atkins ID cases since 2009.  Joel Schneider and Cecil Reynolds have also been active in a similar capacity.  There are more psychologists who come from, or are affiliated with, the field of school psychology who have been prominent consultants/experts to lawyers and the courts re Atkins cases.  

Perhaps some of these briefs should be assigned readings (in intellectual assessment courses or special topic seminars) for graduate students being trained in the art and science of intelligence testing and interpretation.

The use of the Woodcock-Johnson Fourth Edition (WJ IV) GIA Cognitive IQ score in intellectual disability (ID) determination

The WJ IV Cognitive GIA in iintellectual disability (ID) assessment from Kevin McGrew

Stability of intelligence from infancy through adolescence

Stability of intelligence from infancy through adolescence: An autoregressive latent variable model (article link)

Huihui Yua, D. Betsy McCoach, Allen W. Gottfriedc, Adele Eskeles Gottfriedd

a Yale University, United States b University of Connecticut, United States c Fullerton Longitudinal Study, California State University, Fullerton, United States d California State University, Northridge, United States

A B S T R A C T

This study examined the stability of the latent construct of intelligence from infancy through adolescence, using latent variable modeling to account for measurement error. Based on the Fullerton Longitudinal Study data, the present study modeled general intelligence across four developmental periods from infancy through adolescence. The Fullerton Longitudinal Study included twelve assessments of intellectual performance over a sixteen-year interval. Three assessments of intellectual performance at each of four developmental periods served as in-dicators of latent intelligence during infancy (1, 1.5, and 2 years old), preschool (2.5, 3, and 3.5 years old), childhood (6, 7, and 8 years old), and adolescence (12, 15, and 17 years old). Intelligence exhibited a high degree of stability across the four developmental periods. For instance, infant intelligence revealed a strong cross-time correlation with preschool intelligence (r = 0.91) and moderate correlations with childhood and adolescent intelligence (r = 0.69 and 0.57, respectively). Intelligence followed a stage-autoregressive pattern whereby correlations between IQ scores decreased as the timespan between assessment waves increased. Further, from infancy to adolescence, the effect of intelligence during earlier periods was completely mediated by intelligence during the adjacent developmental period. In contrast to much prior research, this study demonstrated the stability of general intelligence, beginning in infancy.

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Meta-analysis supports cognitive ability differentiation hypotheses (SLODOR)

A B S T R A C T

The cognitive ability differentiation hypothesis, which is also termed Spearman's Law of Diminishing Returns, proposes that cognitive ability tests are less correlated and less g loaded in higher ability populations. In ad-dition, the age differentiation hypothesis proposes that the structure of cognitive ability varies across respondent age. To clarify the literature regarding these expectations, 106 articles containing 408 studies, which were published over a 100-year time span, were analyzed to evaluate the empirical basis for ability as well as age differentiation hypotheses. Meta-analyses provide support for both hypotheses and related expectations. Results demonstrate that the mean correlation and g loadings of cognitive ability tests decrease with increasing ability, yet increase with respondent age. Moreover, these effects have been nearly constant throughout the century of analyzed data. These results are important because we cannot assume an invariant cognitive structure for dif-ferent ability and age levels. Implications for practice as well as drawbacks are further discussed.

More on Greenspan's model of personal competence: Relationship between IQ and social, practical, and conceptual abilities

I am pleased to see that, after a relatively long draught in published research, someone is again investigating the relations between general intelligence, and the primary domains of adaptive behavior, in models (that when examined closely) that are investigating aspects of Greenspan's' model of personal competence. The title, abstract, and key figure from this new research follow. The article can be read here. Kudos to these researchers

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My primary criticism of this study is that it completely ignores the primary foundation research in this area that occurred between 1990 and 2000, some of which are the primary research studies cited in the AAIDD manuals to support the domains of practical, conceptual and social competence (Greenspan's model). I have provided a list of that research, and results from the most prominent article from that group of researchers, below.












Yes, my name is all over these MIA studies (in the current featured article) so some could see my comments as academic sour grapes for being overlooked. But I see their omission as a lack of scholarly rigor by the researchers and the journal who published the current article. All of the MIA studies can be found at the MindHub--scroll down until you see the list of studies shown above. Then click away and download and read. It would have been nice if the new study results would have been integrated with the extant personal competence research literature.

In the final analysis I am pleased that someone is conducting much needed research on these constructs given the pivotal role they play in the definition and assessment of MR/ID.


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The Death Penalty and Intellectual Disability: AAIDD forthcoming pub--TOC with authors and chapter titles

    

 The Death Penalty and Intellectual Disability: A Guide (1/3/14)*

* Note the above title is as registered by AAIDD with Library of Congress and as presentedon their website. The working title of the task force had been:  Determining Intellectual Disability in the Courts: Focus on Capital Cases

 

As described at the AAIDD publications page:

 In the 2002 landmark decision Atkins v. Virginia 536 U.S. 304, the Supreme Court of the United States ruled that executing a person with intellectual disability is a violation of the Eighth Amendment of the U.S. Constitution, which prohibits “cruel and unusual punishment,” but left states to determine their own criteria for intellectual disability. AAIDD has always advocated against the death penalty for people with intellectual disability and has long provided amicus curiae briefs in Supreme Court cases. Thus, in this comprehensive new book published by AAIDD, notable authors in the field of intellectual disability discuss all aspects of the issues, with a particular focus on foundational considerations, assessment factors and issues, and professional concerns in Atkins assessments. 

                     

Chapter	Titles	Authors
	Preface	Ed Polloway
	Foreword	Honorable Kevin Foley
	Part 1:  Foundational Considerations
1	Guide for Persons with Intellectual Disability and Capital Cases: An Introduction	Edward A. Polloway James R. Patton J. David Smith
2	Intellectual Disability:  A Review of its Definitions and Diagnostic Criteria	Marc J. Tassé
3	Mild Intellectual Disability	Gary Siperstein Melissa Collins
4	Analysis of Atkins Cases	John Blume Karen Salekin
	Part 2:  Assessment Considerations
	A.  General Topics:
5	Concepts of Measurement	Keith Widaman
6	Age of Onset and the Developmental Period Criterion	Stephen Greenspan George Woods Harvey Switzky
	B. Intellectual Functioning:
7	Intellectual Functioning: Conceptual Issues	Kevin McGrew
8	Consideration in the Selection and Analysis of IQ Tests	Dale Watson
9	Variability of IQ scores	Stephen Greenspan J. Gregory Olley
10	Norm Obsolescence: The Flynn Effect	Kevin McGrew
	C. Adaptive Behavior:
11	Evolving Concepts of Adaptive Behavior	Stephen Greenspan
12	Selection of Appropriate Adaptive Behavior Instruments	J. Gregory Olley
13	Challenges in Assessment of Adaptive Behavior in Capital Cases	Caroline Everington Gilbert S. Macvaugh III Karen Salekin Timothy J. Derning
14	Time at Which Disability Must Be Shown in Atkins Cases	J. Gregory Olley
15	Briseño Factors	Stephen Greenspan
	Part 3:  Related Topics
16	Cultural Factors in Assessment	Richard Ruth
17	Assessment Issues: Competence to Waive Miranda Rights and Competence to Stand Trial	Karen Salekin Caroline Everington
18	Considerations of Retrospective Assessment and Malingering	Denis Keyes David Freedman
19	Intellectual Disability, Comorbid Disorders and Differential Diagnosis	George Woods David Freedman Timothy J. Derning
20	School and Other Key Records	James Patton
21	Relevance of Other Assessments in Atkins Evaluations	Karen Salekin Gilbert S. Macvaugh III Timothy J. Derning
22	Professional Issues in Atkins Assessments	Gilbert S. Macvaugh III Mark D. Cunningham Marc J. Tassé