Abstract

Definitions and associated descriptions of the condition now commonly known as intellectual disability serve many functions. The Atkins v. Virginia U.S. Supreme Court decision (2002) has called attention to the importance of clear, objective, and measureable wording of the definition. This article discusses the potential for misunderstanding and misinterpretation of such words as ability and cognitive, the importance of clarifying the role of measurement error and sociocultural factors, and the noncausal relationship between impairment in intelligence and adaptive behavior.

Definition of Intellectual Disability in Criminal Court Cases

The definition of intellectual disability (ID) and its supporting statements that explain and clarify the definition must fulfill many functions. One of these functions is to clarify the meaning and characteristics of the disability when a person who has or may have ID is accused of a crime and appears in court. The common characteristics of people with ID place them at greater risk of contact with the criminal justice system (Hayes, 2012). Thus, any definition should be worded in a way that allows the courts to understand and implement the definition in an objective and fair manner. Although most of the functions of a definition, including legal functions, have international applications, the United States has at least one application of the definition that is not shared with most other countries. The U.S. Supreme Court's 2002 Atkins v. Virginia decision prohibits the death penalty for persons with “mental retardation.” Thus, it is essential that the revision of any definition take into consideration the ways that courts may interpret and apply the definition, knowing that for some people, the court's interpretation will have life or death consequences.

People with ID may appear in court for several reasons. These may involve civil matters, such as guardianship or controversies regarding proper school placement or services. They may also involve criminal matters, which vary greatly in seriousness from minor offenses, such as shoplifting or disruptive behavior in public places, to felonies, such as armed robbery or murder. Hayes (2012) cited studies of the prevalence of ID in the criminal justice system with figures that varied from 1.7 percent to 18.3 percent. An objectively stated and uniformly accepted definition is necessary to gain more accurate estimates of prevalence of offending or prevalence of people with ID in jails and prisons.

Courts should understand the common characteristics of ID to decide whether the matter will be decided by the legal system or referred to the local human service system for informal resolution and the creation of appropriate supports and services that will prevent recidivism. If a defendant has an established diagnosis of ID, that diagnosis will usually be known to the court. However, for individuals whose disability is not visible and who have not been identified by any service provider, judges will have to rely on established definitions of ID if they are to take the disability into account in sentencing. Therefore, it is very important that the prevailing definitions be in reasonable agreement with regard to the name of the condition and the criteria for diagnosis. The following discussion is intended to identify some areas in which the wording of the definition can easily be misunderstood or misinterpreted in court.

Competence to Stand Trial

Although a determination of competence to stand trial (i.e., competence to proceed or adjudicative competence) is not dependent on a definition of ID, defendants with ID may be evaluated to determine whether they meet this standard. The Dusky v. United States (1960) U.S. Supreme Court case affirmed that defendants cannot be brought to trial unless they understand the charges against them and are able to assist their attorney in their own defense. Although the so-called Dusky Standard is interpreted differently from state to state, attorneys and professionals who perform competence evaluations can assist the court by using current definitions of ID to explain the defendant's difficulties in meeting this standard. If the defendant is found not competent to stand trial, he or she may be compelled to participate in “competence restoration” training to meet the Dusky Standard to go to trial. People with ID may have a very difficult time understanding and acting on the abstractions involved in the Dusky Standard, and a clear definition of the disability may assist the court and the professionals to understand the defendant's challenges.

Capital Offenses and Other Felonies

Hearings to determine whether a defendant has an ID under the Atkins decision rely on the adversarial court process in which expert witnesses for the prosecution and the defense present their opinions regarding the diagnosis. As these witnesses are examined and cross-examined, their opinions rest in part on the definition of ID that is recognized in that state or federal jurisdiction. Although these definitions vary, experts typically invoke authoritative sources to support the definition on which their diagnosis is based. In cross-examination, attorneys commonly challenge the basis for the expert's opinion. Such challenges may rest heavily on the wording of the definition. It is, therefore, essential that authoritative definitions are worded in clear and measureable terms to the extent feasible.

IQ or Something Else?

The 2010 AAIDD manual (Schalock et al., 2010) allows for less strict reliance on IQ scores than in the past. This change of emphasis has several important implications for measurement of the so-called “first prong” of the definition. Some experts believe that there is strong support for the use of other measures, such as executive functioning, working memory, or cognitive profiles. If such concepts are introduced into definitions of ID, the concepts must have a valid and well-agreed-on method of measurement. If concepts other than intelligence are included in definitions, the qualifications of experts must include a stronger emphasis on clinical experience with people with ID and training in psychometrics. Regardless of the definition used, experts must rely on an objectively stated definition, rather than on clinical impressions.

The Relationship Between Intelligence and Adaptive Behavior

The fallacious argument has sometimes been made in Atkins cases that a diagnosis of ID requires a showing that the defendant's deficits in adaptive behavior were caused by low intelligence. Such a causal link has never been required by previous AAIDD or American Psychiatric Association (APA) definitions, although the wording of some other definitions or proposed definitions could lead to this conclusion. Previous AAIDD definitions have used wording such as impaired intelligence “is associated with” impaired adaptive behavior (Heber, 1961), or are “existing concurrently with” (American Association on Mental Retardation, 1992; Grossman, 1973, 1977, 1983), or impairment exists “both in intellectual functioning and in adaptive behavior “ (American Association on Mental Retardation, 2002; Schalock et al., 2010). The APA has used similar language. The Diagnostic and Statistical Manual of Mental Disorders (DSM) used the phrases “associated with” (1968) and “accompanied by” (1987, 1994, 2000).

This history is important to note, because a less careful investigator may check online sources and find, for example, the Encyclopedia of Mental Disorders (2013), which defines “mental retardation” as “a level of intellectual functioning … that is well below average and results in significant limitations in the person's daily living skills (adaptive functioning).” If such a definition were accepted in court, it would require the expert to do the impossible task of proving that the defendant's low intelligence “resulted in” impaired adaptive behavior.

Ability

Definitions or the interpretations of definitions in court may refer to the defendant's ability, which is a theoretical construct similar to potential, neither of which can be validly measured for an individual. Whatever is implied by use of the word ability is probably adequately covered by conventional measures of intelligence.

What is Cognitive?

A good example of the importance of precise language in definitions and the supporting language accompanying definitions is use of the word, “cognitive.” Although it is sometimes used as a euphemism for intelligence, cognitive impairment more commonly refers to the results of brain injury or dementia. The inclusion of “cognitive” in descriptions of ID risks confusion and misleading conclusions.

Measurement Error

Reports of psychological or educational measurement by expert witnesses routinely take into account measurement error in their findings, for instance by reporting the standard error of measurement or a confidence interval of the test scores. Some definitions of ID (or mental retardation) in state statutes related to the death penalty (or definitions from civil law that are adapted for use in criminal court) fail to mention measurement error and can be interpreted to prohibit the consideration of measurement error. Authoritative definitions by professional organizations must make the importance of measurement error clear and provide expert witnesses a reference to support the application of this important psychometric principle.

Sociocultural Factors

Definitions of ID are typically brief, easily understood statements that are accompanied by more extensive supportive material that clarifies the meaning and applications of the definition for different purposes. Virtually all expert witnesses would agree that sociocultural factors must be taken into account when the purpose of a definition of ID is to plan individualized services for a person with ID. In a criminal courtroom application (and to a certain extent in other legal hearings concerning eligibility, such as eligibility for Social Security Income disability benefits), the definition is used to make a black-or-white decision about whether the diagnosis applies to the defendant. To the extent that the diagnostic evaluation relies on standardized tests, sociocultural factors are taken into consideration in the norming of the tests. That is, the tests' norm groups match the demographics of the most recent U.S. census, which includes people of varied sociocultural backgrounds. To the extent that the evaluation relies on information from non-normed sources (e.g., interviews, records reviews, informal tasks), the expert must use careful clinical judgment in taking sociocultural factors into account.

If the definition of ID uses words such as “impairment relative to one's sociocultural background,” it invites subjective alterations of findings. Widaman and Siperstein (2009) have thoroughly addressed the problem of subjective alteration of scores to compensate for cultural and socioeconomic factors. This problem has been addressed for standardized testing of intelligence and educational achievement for defendants from Spanish-speaking countries by the Batería III Woodcock-Muñoz (Woodcock, Muñoz-Sandoval, McGrew, & Mather, 2007), which is appropriately standardized for this use. However, the assessment of adaptive functioning must rely to some extent on the judgment of the expert. A caution from the AAIDD User's Guide: Mental Retardation (10th edition) must apply to the expert's judgment: “Do not allow cultural or linguistic diversity to overshadow or minimize actual disability” (Schalock et al., 2007, p. 23).

Current Functioning?

It is common for definitions to refer to deficits in current functioning. Although this wording is useful in acknowledging that the individual's functioning could have been different at an earlier time, it creates ambiguity in Atkins cases with regard to when the impaired functioning must have occurred. The AAIDD (Schalock et al., 2010) and other definitions require that impaired functioning be documented (although not diagnosed) in childhood, and the rationale for the Atkins decision's finding of less culpability rests on impairment at the time of the crime, but opinions differ with regard to the need to document impairment in current functioning. State law and legal precedent in most of the 33 states that currently impose the death penalty require that the defendant in an Atkins proceeding prove that his or her current functioning is impaired in both intellectual and adaptive functioning. Although current intellectual functioning of an incarcerated defendant can be assessed by an appropriate IQ test, AAIDD (Schalock et al., 2010, 2012) has emphasized that adaptive functioning is typical community functioning, which cannot be validly assessed for a person in jail or prison. The supporting material for any definition of ID should clarify that impaired current functioning does not refer to functioning in prison or other settings where behavior is restricted.

Summary

The name of the condition that we currently refer to as ID, its definition, and the supportive materials that explain the definition have changed continually since the AAIDD's first definition over 100 years ago (Committee on Classification of Feeble-Minded, 1910), and authoritative information about ID will likely continue to change in the future. These changes are necessary to address current knowledge of the condition and changing applications of definitions. Each change must be carefully considered in light of its current and anticipated uses. Increasing recent attention to people with ID in the criminal justice system has highlighted some of the wording in definitions that can be interpreted in different ways, misunderstood, or distorted. Such imprecise wording can undermine the purposes of the definition, and in the case of defendants with ID in the criminal justice system, it has the potential to deny defendants their legal rights. Future changes in definitions should be carefully considered with regard to ways that the wording of the definitions may be applied in court or in other legal settings.

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Author notes

Author:

J. Gregory Olley (greg.olley@cidd.unc.edu), Carolina Institute for Developmental Disabilities, CB 7255, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7255.