Snap Shot
- The question: How accurately do children and adults with intellectual disability remember and report events, how vulnerable are they to leading questions and pressure, and what interviewing practices help them give their best evidence?
- What the research shows: In free recall, people with mild intellectual disability generally report less than their peers, but in the few studies able to check, mostly of staged events, what they reported was generally accurate. Accuracy falls with closed, leading, presumptive, and repeated questions, and acquiescence and interrogative suggestibility are higher on average, especially as the level of disability increases. Open-ended methods increase correct information without measurable increases in error, and suspects with intellectual disability often understand Miranda warnings poorly; reviews identify intellectual disability as a characteristic that increases the risk of false confession, although in one large self-report study of prisoners other conditions were stronger predictors.
- What it does not show: The diagnosis does not make a witness incompetent or an account unreliable, and a high suggestibility score does not show that a particular account or confession is false. Most studies are small laboratory studies of mild disability, and very little research has tested intermediaries or other adaptations with adults who have intellectual disability.
- The law: Every person is presumed competent to testify (Fed. R. Evid. 601; Mil. R. Evid. 601; A.R.S. § 13-4061), and the court controls the mode of questioning (Rule 611(a)). Expert testimony is governed by Rule 702 and Houser, and in Arizona by Chapple, Nordstrom, and Lindsey; a Miranda waiver must be knowing and intelligent as well as voluntary; Atkins, Hall, and Moore govern capital eligibility.
- Issues for each side: Prosecutors can rely on the finding that free narratives of witnesses with intellectual disability were generally accurate in the few studies able to check, and should obtain it through open, recorded interviews; defense counsel can examine whether answers were shaped by closed, leading, or repeated questions and whether a client understood the warnings, without treating the diagnosis as a reason to disbelieve.
Intellectual disability is a condition that begins during the developmental period and involves deficits in intellectual functions, such as reasoning, problem solving, and learning, together with deficits in adaptive functioning in everyday life; its severity is classified as mild, moderate, severe, or profound on the basis of adaptive functioning (American Psychiatric Association, 2022). Older research used the terms “mental retardation” or, in the United Kingdom, “learning disability.” Children with disabilities as a group had higher odds of sexual violence than children without disabilities in a meta-analysis of observational studies (pooled odds ratio 2.88; the underlying rates are not given here; Jones et al., 2012), and people with intellectual disability are often the only witnesses to an alleged crime (Ternes & Yuille, 2008). They also come before the courts as suspects and defendants.
The diagnosis alone says little about whether a given account is accurate. The research shows that these witnesses can give accurate accounts, that the form of questioning strongly affects accuracy, and that the level of disability is an important moderator; the same points apply to a suspect in interrogation.
This paper summarizes research on free recall, question types, suggestibility and acquiescence, identification, interviewing adaptations, Miranda comprehension, and false confession risk, and the federal, military, and Arizona law that bears on them.
Free Recall: Accurate but Less Complete
The most consistent finding is that people with intellectual disability, when allowed to describe an event in their own words, provide less information than people without disability, but that the information they provide is mostly accurate. A review of the research on witnesses with intellectual disability reached that conclusion and added that their accounts are strongly influenced by the methods of questioning (Kebbell & Hatton, 1999). In a study in which adults with and without intellectual disability had their photographs taken by a confederate and were interviewed one to two weeks later, the participants with intellectual disability reported significantly fewer details, and the details reported by both groups were mainly accurate (Ternes & Yuille, 2008).
Studies of children point the same way. Children with intellectual disability who were questioned a day after a staged live event matched same-age peers on free recall, general questions, and open-ended questions (Henry & Gudjonsson, 1999). In a follow-up study, children with mild intellectual disability performed as well as same-age peers in free recall and were as able to resist misleading questions, although they did less well on general follow-up questions and changed answers to specific questions more often when interviewed again two weeks later; children with moderate intellectual disability did markedly worse on nearly every question type (Henry & Gudjonsson, 2003). The free narrative is usually the most dependable part of the evidence.
Closed, Leading, and Repeated Questions
Accuracy declines as questioning moves away from open invitations. Children with intellectual disability were more suggestible than same-age peers in response to closed misleading questions, though not more suggestible than younger children of similar mental age (Henry & Gudjonsson, 1999). In an experiment with 41 adults with mild intellectual disability who watched a short film, misleading questions produced a misinformation effect on a later recognition test, and questions that presumed the misleading detail to be true, whether phrased as closed or open questions, produced the largest effects (Bowles & Sharman, 2014). A presumptive question is one that assumes a detail the witness has not reported.
Repetition is a particular concern. In transcripts of Swedish investigative interviews with 33 children and young people with intellectual disabilities who were alleged victims of sexual abuse, the interviewees changed their answers about 40% of the time when option-posing and suggestive questions were repeated, and questions were repeated at least once about 6% of the time in the interviews examined; the number of repeated questions behind the 40% was not located in the published abstract (Cederborg et al., 2009). Because the cases were real, the researchers could not tell which answers were correct; the finding shows that repetition makes an account harder to evaluate. The reason was not tested; one suggested explanation is that a witness reads a repeated question as a sign that the first answer was wrong.
Suggestibility and Acquiescence
Interrogative suggestibility, measured with the Gudjonsson Suggestibility Scales, has two components: yielding to leading questions and shifting answers after negative feedback. Acquiescence is a tendency to agree with a closed question whatever it asks. Adults with mild intellectual disability were more suggestible than adults of average ability, mainly because they yielded more to leading questions, and they also confabulated and acquiesced more (Clare & Gudjonsson, 1993). In a study of 110 children and 221 adults grouped by IQ, both children and adults with intellectual disability had much poorer memory and higher suggestibility than peers of average intelligence; memory explained only part of the difference, and shifting under negative feedback differed by intellectual level among children but not among adults (Gudjonsson & Henry, 2003). A 2026 meta-analysis found large effects on every Gudjonsson Suggestibility Scale index for people with intellectual disability and comparable or higher scores for people with fetal alcohol spectrum disorder whose IQs often fall above the diagnostic threshold (Gilbert et al., 2026). A review of children’s suggestibility likewise linked intellectual impairment to greater suggestibility (Klemfuss & Olaguez, 2020).
Standardized scores have limits. In the eyewitness studies, scores on the Gudjonsson scales predicted performance only modestly to moderately (Henry & Gudjonsson, 2003), and relationships between the scales and eyewitness performance were not consistent across groups (Henry & Gudjonsson, 1999). A high score indicates a vulnerability to be considered alongside the interview itself; it does not establish that a particular answer was the product of suggestion, and a low score does not establish that a witness was not led.
Eyewitness Identification
Identification research is sparse. In the photograph study, adults without intellectual disability made more correct identifications than adults with intellectual disability when the photographer was in the lineup; when the photographer was absent, the groups did not differ significantly, although only the comparison group performed better than chance (Ternes & Yuille, 2008). These small-sample results suggest fair lineup procedures matter at least as much for these witnesses.
Interviewing Adaptations
In a study of adults with mild intellectual disability who watched a staged theft, the cognitive interview, which combines rapport, free report, context reinstatement, and open-ended questioning, increased correct recall of persons, actions, and the gist of conversation compared with a structured interview, without increasing incorrect or confabulated details (Clarke et al., 2013). In a study of 48 adults with intellectual disability, practicing with open-ended questions about an unrelated event early in the interview led to more detail about the target event than practice with specific questions, with no increase in inaccurate details (Yi, 2025). These findings support simple language, one idea per question, open prompts tied to what the witness has said, and avoiding presumptive, forced-choice, and repeated questions.
England and Wales provide registered intermediaries, communication specialists who advise on questioning vulnerable witnesses. Experimental research on their effectiveness is limited; in one study, typically developing children assisted by an intermediary made more accurate identifications from perpetrator-present lineups than children given standard best-practice lineups (Wilcock et al., 2018). Comparable studies with adults who have intellectual disability have not been identified. American courts have not adopted an intermediary system; the comparable tools are the court’s control over the mode of questioning and accommodations arranged by the parties.
Competency to testify is a separate question. In an assessment of 49 adults with intellectual disability who were potential witnesses of ill-treatment, most of those with a Full Scale IQ of 60 or above showed a basic understanding of the oath, while fewer with lower scores did; some who could not explain the oath nonetheless understood “truth” and “lie” when asked about concrete examples (Gudjonsson et al., 2000). The authors cautioned that requiring an explanation of the oath would exclude useful witnesses.
Suspects: Miranda Comprehension and False Confession Risk
In a study of 62 people with intellectual disability, Miranda comprehension was substantially poorer than in the normative sample of a standardized assessment, prior knowledge of the rights was limited, comprehension improved little after hearing a warning, and acquiescence was markedly higher; verbal ability predicted recall and vocabulary of the warning, but IQ did not predict misconceptions or acquiescence (Erickson et al., 2020). In 820 pretrial defendants, those with IQs between about 70 and 85, who do not meet criteria for intellectual disability, also showed impaired recall and understanding of the warnings and often held misconceptions, such as believing the officers were on their side (Tazi & Rogers, 2023).
A scientific review of police-induced confessions treated intellectual disability as one of the personal characteristics that increase the risk of false confession and recommended recording interrogations (Kassin et al., 2010). Self-report data add nuance: in a study of 386 Scottish prisoners that assessed mild intellectual disability among other conditions, the predictors reported as significant were conduct disorder, ADHD, psychological distress and psychiatric symptoms, and compliance, with conduct disorder and ADHD the strongest (Gudjonsson et al., 2021). The research supports careful attention to how a suspect with intellectual disability was questioned and what the suspect understood; it does not show that a particular confession is false. Interrogation is addressed in the False Confessions resources.
Limits of the Evidence
Most studies are small, many involve children, and most concern mild intellectual disability. Films and staged events lack the stress of a real offense, field studies cannot determine which answers were correct, and definitions and IQ cutoffs vary. The research describes how groups perform under particular questioning conditions; it cannot establish whether a particular witness with intellectual disability accurately remembered a particular event or whether a particular answer was the product of a particular question.
Questions to Ask About This Research
When Kebbell and Hatton (1999) or Ternes and Yuille (2008) is cited to show that free recall by people with intellectual disability is accurate though less complete, counsel should ask who was studied and whether it applies to this person: the findings concern mostly mild disability, and Henry and Gudjonsson (2003) found markedly poorer performance among children with moderate disability. When Henry and Gudjonsson (1999, 2003) is cited, counsel should note that the participants were children. When Cederborg et al. (2009) is cited for the 40% figure, counsel should ask what was counted (answer changes in real interviews, without knowledge of which answer was true). When a Gudjonsson Suggestibility Scale score or a meta-analysis such as Gilbert et al. (2026) is offered, counsel should ask whether a group difference on a standardized test shows that this person yielded to suggestion in this interview, given that the scales only modestly predicted eyewitness performance. These questions are explained in “Reading Research Claims: A Guide for Attorneys” on this site.
Intellectual Disability, Memory, and the Law
Federal and Military Standards
Every person is competent to be a witness unless the rules provide otherwise (Fed. R. Evid. 601; Mil. R. Evid. 601), so intellectual disability ordinarily goes to the weight of testimony rather than to its admissibility. The court’s reasonable control over the mode and order of examining witnesses (Fed. R. Evid. 611(a); Mil. R. Evid. 611(a)) provides the basis for accommodations such as plain-language questions and breaks; leading questions on direct examination are permitted when necessary to develop a witness’s testimony (Fed. R. Evid. 611(c); Mil. R. Evid. 611(c)). Expert testimony about intellectual disability and memory is governed by Federal Rule of Evidence 702, as amended December 1, 2023, under Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) and Kumho Tire Co. v. Carmichael (1999), which extended the gatekeeping obligation to all expert testimony, including testimony based on technical or other specialized knowledge. Military Rule of Evidence 702 tracks the federal rule; under Military Rule of Evidence 1102, the 2023 amendment became part of the military rule in 2025 (Joint Service Committee on Military Justice, 2025), and practitioners should confirm current text. Military judges also apply the six United States v. Houser (1993) factors.
For suspects, a waiver of Miranda v. Arizona (1966) rights must be voluntary and made with full awareness of the rights and the consequences of abandoning them (Moran v. Burbine, 1986), and the research on Miranda comprehension bears most directly on whether a waiver was knowing and intelligent. Because coercive police activity is a necessary predicate for finding a confession involuntary (Colorado v. Connelly, 1986), intellectual disability alone does not make a statement involuntary. In the military, a waiver after Article 31 and counsel warnings must be made freely, knowingly, and intelligently, with an affirmative acknowledgment that the accused understands the rights (Mil. R. Evid. 305(e)(1)). In capital cases, Atkins v. Virginia (2002) held that the Eighth Amendment bars execution of people with intellectual disability, noting among its reasons the possibility of false confessions (536 U.S. at 320–321); Hall v. Florida (2014) held that a state may not treat an IQ score above 70 as conclusive without accounting for measurement error; and Moore v. Texas (2017) required courts to be informed by current medical standards.
Arizona
In an Arizona criminal trial every person is competent to be a witness (A.R.S. § 13-4061), and Arizona Rule of Evidence 611(a) likewise gives the court control over the mode of examining witnesses. Arizona Rule of Evidence 702 adopted the Daubert standard effective January 1, 2012, and was amended effective January 1, 2024, to conform to the 2023 federal amendment (Ariz. Sup. Ct. Order R-23-0004). State v. Salazar-Mercado (2014) permits general, educational expert testimony that satisfies Rules 702 and 403. State v. Chapple (1983), Arizona’s leading case on expert testimony about the reliability of eyewitness memory, held that excluding a qualified expert was an abuse of discretion on its facts, while leaving admission generally within the trial court’s discretion; State v. Nordstrom (2001) upheld limiting such an expert to general factors. Experts may not opine on a particular witness’s credibility (State v. Lindsey, 1986, 149 Ariz. at 475). The court decides the voluntariness of a confession outside the jury’s presence, and the jury may weigh evidence bearing on voluntariness (A.R.S. § 13-3988). Arizona’s capital statute, A.R.S. § 13-753, contains its own provisions on intellectual disability in capital cases.
Special Issues in Legal Practice
The principles described above apply with equal force to every party in a legal proceeding. The science operates the same way regardless of who is asking the questions, and the research summarized here does not by itself favor either side. What differs between the parties is not the science but the vantage point — the particular places where these issues tend to surface, and the particular errors each party is best positioned to guard against. The two summaries below identify those recurring issues. They are offered for orientation, not as litigation strategy; in every case the controlling question is what the evidence in that case will, and will not, support, and the expert’s role is to inform the trier of fact rather than to advocate for either side.
Special Issues for Prosecutors
The research supports several propositions prosecutors can legitimately present. A witness with intellectual disability is competent to testify, and in the few studies able to check, mostly of staged events, free recall by such witnesses, particularly those with mild disability, was generally accurate even when they reported less; closed questions carry more risk. A short or simple account is not, by itself, a sign of inaccuracy, and general expert testimony can help jurors avoid assuming that a witness with intellectual disability cannot be believed. In the available studies, open-ended interviewing, the cognitive interview, and narrative practice increased information without measurable increases in error, and prosecutors can ensure that an early account is obtained that way, recorded, and corroborated where possible.
The research also counsels caution. Details obtained through closed, presumptive, forced-choice, or repeated questions are less dependable, and an answer that changed after a question was repeated is difficult to evaluate. Witnesses with intellectual disability acquiesce more, and an interview record that consists largely of “yes” answers to leading questions is vulnerable for that reason. A confession from a suspect with intellectual disability should be evaluated in light of research on Miranda comprehension, suggestibility, and false confession risk, and a complete recording of the interrogation is the best protection for a statement the State intends to rely on.
Special Issues for Defense
The research supports several propositions defense counsel can legitimately present. Witnesses with intellectual disability are more vulnerable than their peers to leading, presumptive, and repeated questions, and their answers can reflect the demands of the interview rather than their memory, even when they are entirely sincere. General expert testimony, with a close reading of how each detail was elicited, can help the factfinder separate the free narrative from answers shaped by questioning. For a client with intellectual disability, the research on Miranda comprehension, acquiescence, and suggestibility supports examining what the client understood about the rights and how the interrogation was conducted.
The research also counsels caution about the limits that apply to the defense. People with intellectual disability can and do give accurate testimony; free recall is often accurate, and in one study children with mild disability resisted misleading questions as well as their same-age peers. A high suggestibility score is not proof that an answer or a confession was false, and an expert may not tell the factfinder that a particular witness is not credible. In one large self-report study of prisoners that examined mild intellectual disability, conduct disorder and ADHD were the strongest predictors of reported false confessions, so testimony about a client’s statement is strongest when it rests on the record of the interrogation rather than on the diagnosis alone.
This paper is for educational purposes only and is not legal advice. The author is a psychologist, not an attorney; summaries of law are general and must be verified against current authority or with a licensed attorney.
References
American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.). https://doi.org/10.1176/appi.books.9780890425787
Bowles, P. V., & Sharman, S. J. (2014). The effect of different types of leading questions on adult eyewitnesses with mild intellectual disabilities. Applied Cognitive Psychology, 28(1), 129–134. https://doi.org/10.1002/acp.2953
Cederborg, A.-C., Danielsson, H., La Rooy, D., & Lamb, M. E. (2009). Repetition of contaminating question types when children and youths with intellectual disabilities are interviewed. Journal of Intellectual Disability Research, 53(5), 440–449. https://doi.org/10.1111/j.1365-2788.2009.01160.x
Clare, I. C. H., & Gudjonsson, G. H. (1993). Interrogative suggestibility, confabulation, and acquiescence in people with mild learning disabilities (mental handicap): Implications for reliability during police interrogations. British Journal of Clinical Psychology, 32(3), 295–301. https://doi.org/10.1111/j.2044-8260.1993.tb01059.x
Clarke, J., Prescott, K., & Milne, R. (2013). How effective is the cognitive interview when used with adults with intellectual disabilities specifically with conversation recall? Journal of Applied Research in Intellectual Disabilities, 26(6), 546–556. https://doi.org/10.1111/jar.12049
Erickson, S. L., Salekin, K. L., Johnson, L. N., & Doran, S. C. (2020). The predictive power of intelligence: Miranda abilities of individuals with intellectual disability. Law and Human Behavior, 44(1), 60–70. https://doi.org/10.1037/lhb0000356
Gilbert, D. J., Azumara, S. I., Wheatcroft, J. M., Steele, K., Cook, P., Mukherjee, R., Gudjonsson, G., & Brown, N. N. (2026). FASD and intellectual disability equivalence: A meta-analysis of suggestibility during forensic interviews. Behavioral Sciences & the Law, 44(3), 450–460. https://doi.org/10.1002/bsl.70052
Gudjonsson, G. H., Gonzalez, R. A., & Young, S. (2021). The risk of making false confessions: The role of developmental disorders, conduct disorder, psychiatric symptoms, and compliance. Journal of Attention Disorders, 25(5), 715–723. https://doi.org/10.1177/1087054719833169
Gudjonsson, G. H., & Henry, L. (2003). Child and adult witnesses with intellectual disability: The importance of suggestibility. Legal and Criminological Psychology, 8(2), 241–252. https://doi.org/10.1348/135532503322363013
Gudjonsson, G. H., Murphy, G. H., & Clare, I. C. H. (2000). Assessing the capacity of people with intellectual disabilities to be witnesses in court. Psychological Medicine, 30(2), 307–314. https://doi.org/10.1017/S003329179900149X
Henry, L. A., & Gudjonsson, G. H. (1999). Eyewitness memory and suggestibility in children with mental retardation. American Journal on Mental Retardation, 104(6), 491–508. https://doi.org/10.1352/0895-8017(1999)104<0491:EMASIC>2.0.CO;2
Henry, L. A., & Gudjonsson, G. H. (2003). Eyewitness memory, suggestibility, and repeated recall sessions in children with mild and moderate intellectual disabilities. Law and Human Behavior, 27(5), 481–505. https://doi.org/10.1023/A:1025434022699
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Jones, L., Bellis, M. A., Wood, S., Hughes, K., McCoy, E., Eckley, L., Bates, G., Mikton, C., Shakespeare, T., & Officer, A. (2012). Prevalence and risk of violence against children with disabilities: A systematic review and meta-analysis of observational studies. The Lancet, 380(9845), 899–907. https://doi.org/10.1016/S0140-6736(12)60692-8
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Legal Authorities
Atkins v. Virginia, 536 U.S. 304 (2002).
Colorado v. Connelly, 479 U.S. 157 (1986).
Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).
Hall v. Florida, 572 U.S. 701 (2014).
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999).
Miranda v. Arizona, 384 U.S. 436 (1966).
Moore v. Texas, 581 U.S. 1 (2017).
Moran v. Burbine, 475 U.S. 412 (1986).
State v. Chapple, 135 Ariz. 281, 660 P.2d 1208 (1983).
State v. Lindsey, 149 Ariz. 472, 720 P.2d 73 (1986).
State v. Nordstrom, 200 Ariz. 229, 25 P.3d 717 (2001).
State v. Salazar-Mercado, 234 Ariz. 590, 325 P.3d 996 (2014).
United States v. Houser, 36 M.J. 392 (C.M.A. 1993).
U.S. Const. amend. VIII.
10 U.S.C. § 831 (Article 31, Uniform Code of Military Justice).
Ariz. Rev. Stat. Ann. § 13-753.
Ariz. Rev. Stat. Ann. § 13-3988.
Ariz. Rev. Stat. Ann. § 13-4061.
Fed. R. Evid. 601, 611, 702.
Mil. R. Evid. 305, 601, 611, 702, 1102.
Ariz. R. Evid. 611, 702.
Ariz. Sup. Ct. Order R-23-0004 (amending Ariz. R. Evid. 702, effective Jan. 1, 2024).
Related topic papers: Memory in Special Populations · Suggestibility of Children’s Memory · ADHD and Memory · Working Memory · Improving Eyewitness Memory · Memory Expert Testimony
Related topics from Arizona Forensic Services: False Confessions · False Confessions: Suggestibility