Intellectual Disability (ID) is an impairment of general mental abilities that impacts an individual’s ability to function with both conceptual and practical tasks. Individuals with ID can struggle with issues such as reasoning, social interactions, job responsibilities, and personal care. The 2013 revisions to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Health Disorders (DSM-5) changed the diagnosis process so that a diagnosis of ID is no longer based on IQ scores alone, although a standardized assessment is still part of the diagnosis process. An individual with ID typically has an IQ of 70 or below, and can only be considered ID if symptoms begin during the individual’s childhood. It often co-occurs with other conditions such as depression, attention-deficit/hyperactivity disorder, and autism spectrum disorder. There are a variety of causes for ID, including genetic, physical (the result of some infections or malnutrition), and environmental (such as drug or alcohol use during pregnancy, complications during pregnancy, or oxygen depreciation during or after birth).
Intellectual disability used to be referred to as “mental retardation,” a derogatory term mostly no longer in use, even though it might still appear in some texts, programs, laws, or regulations.
Signs of Intellectual Disability
There are three domains in which adaptive functioning is impaired for individuals with ID:
The Conceptual Domain:
- Skills in language, reading, writing, math, reasoning, knowledge, and memory.
The Social Domain:
- Empathy, social judgment, interpersonal communication skills, the ability to make and retain friendships, and similar capacities.
The Practical Domain:
- Self-management in areas such as personal care, job responsibilities, money management, recreation, and organizing school and work tasks.
An individual with ID begins showing symptoms early in childhood as he or she develops more slowly than their peers and has more trouble learning. ID tends to manifest in common symptoms such as:
- Learning more slowly than other children of the same age.
- Rolling over, sitting up, crawling, or walking later than developmentally appropriate.
- Difficulty communicating or socializing with others.
- Lower than average scores on IQ tests.
- Difficulties speaking, or beginning to speak later than developmentally appropriate.
- Having problems remembering things.
- An inability to connect actions with consequences.
- Difficulty with problem-solving or logical thinking.
- Trouble learning in school.
- An inability to do everyday tasks like getting dressed or using the restroom without help.
How Intellectual Disability Might Impact Behavior
Intellectual disability is a lifelong condition that cannot be cured, but services and support – when available – play an important role and can enable the person to thrive. However, the functional gaps between adults with ID and adults without the condition may grow wider over time. Accordingly, adults with ID will not always act in a way that other adults would.
Individuals with ID may have a strong need to be accepted by others, which can lead them to agree to help with criminal activities to gain friendship; it may be that the individual with ID does not understand that the actions are criminal, or that there may be consequences for the behavior. When questioned by law enforcement, individuals with ID may unintentionally misunderstand questions and give answers that leave them more vulnerable to arrest and incarceration.
Although each individual with ID is unique, there are some common behaviors that may complicate their interactions with the criminal justice system. Individuals with ID may:
- Hide their disability.
- Pretend to understand their rights even if they do not.
- Not understand or respond to commands, instructions, etc.
- Act upset at being detained and/or try to run away.
- Try to appease interrogators by saying what the police want to hear.
- Have difficulty describing facts or details.
- Confess to crimes they did not commit.
- Be easily influenced by and eager to please others.
- Be unaware of how serious or dangerous the situation is.
Resources for More Information
 Robert Perkse, “Perske’s List: False Confessions From 75 Persons With Intellectual Disability,” American Association on Intellectual and Development Disabilities, October 2011, https://aaidd.org/docs/default-source/publications/perske-s-list-false-confessions-from-75-persons-with-intellectual-disability.pdf?sfvrsn=0.
Download the Fact Sheet
The CCRI worked with the Bazelon Center for Mental Health Law to produce this Fact Sheet in 2017. Please note that this document only offers an overview and simply serves as a starting point in considering the impacts of a particular condition on an individual. This Fact Sheet does not provide the level of detail, citations, medical terminology, or full diagnostic criteria that an expert or medical professional would need to make a diagnosis or that a lawyer would need to have to advocate most effectively on behalf of her client.