Child witnesses with ‘mild’ intellectual disabilities just as capable

Child witnesses with ‘mild’ intellectual disabilities are as reliable as other children with same mental age

By Deirdre Brown and , | March 2016 

Research demonstrates reliability of their evidence and paves the way for this vulnerable group to participate properly in legal systems.

Child witnesses with ‘mild’ intellectual disabilities are typically just as reliable as other children of the same mental age, according to our research. We found, for example, that the testimony of a 12-year-old child who has the thinking skills of a 9-year-old is as detailed and reliable as that of a typical 9-year-old child. ‘Mild’ means children whose mental functioning is in the bottom 1 per cent of the population.

These findings from our research, conducted in the UK, demonstrate that once investigators know such a child’s developmental or mental age, they can pitch interviews at the level they would adopt for a typically developing child of that age.

“Investigators should know a child’s developmental or mental age before interviews so that they can tailor questions appropriately, assess testimony realistically and act confidently on the evidence.”

Higher risk of abuse

Children with intellectual disabilities are particularly vulnerable, but they are often excluded from legal proceedings. Studies suggest that one in three children with disabilities experiences some form of abuse or maltreatment, partly because such children rely more on others for care. Their needs may be so great and resources may be so stressed – either within families or in institutional settings – that they are at risk of abuse. Yet maltreatment of such children is less likely to be investigated because, according to research, legal systems, police and interviewers typically lack confidence in what they say. Practitioners, lawyers, judges and jurors should therefore be informed that children with ‘mild’ intellectual disabilities have the same accuracy of recall as do children of the same mental or developmental age. Disseminating this finding could improve child protection considerably.

Early, open-ended interviews best for child witnesses

Our findings also show that children should be interviewed early on. All the children in our study, regardless of their intellectual abilities, recalled more information more accurately after six months if they had first been interviewed after only a short delay. Also, open-ended questioning produced higher-quality recall than did a more focussed style of questioning that some professionals adopt when they interact with a child with intellectual disability.

We examined the performance of children whose mental functioning was in the bottom 1 per cent of the population. Almost all attended special schools and had special curricula and teaching aid. The children with intellectual disabilities were between 7 and 12 years old and had one of two levels of disability: 46 were in the ‘mild’ range and 34 in the more severe ‘moderate’ range. We studied an additional 116 children with typical intellectual development, making a total of 196 children. All took part in an event at their school and were later questioned about it.

The interviews followed a protocol that is internationally promoted as the best way to assess allegations of child maltreatment. Half the children were interviewed a week after the event and then again six months later. The other half were interviewed only once, six months after the event.

Severity of intellectual disability is important

The children with ‘mild’ intellectual disability typically had poorer recall than did mainstream children of the same age. However, their performance almost invariably matched that of children of the same mental or developmental age. This was true with regard both to details about the event and to how they answered leading or misleading questions that might be used in legal cross-examination. The narrative quality of their storytelling was also comparable.

Our findings make a compelling case that investigators should be told the mental age of a child with intellectual disabilities before interviewing the child. Investigators often lack this information. Studies show that disabilities are often neither recognised nor documented and that judges, for example, often don’t modify their questioning to take disabilities into account.

Providing information about children’s mental age – and acting on it – would be a considerable breakthrough. Most people with intellectual disability don’t look different from anyone else, and they may not act differently from the mainstream population. Their disability may not become clear for some time. So being briefed on mental age is important. Even then, it can be challenging to sit in front of someone who looks like a 12-year-old and keep in mind that the person is functioning like a 9-year-old.

Our findings were different for children with more severe ‘moderate’ disability. They had poorer recall than did mainstream children of the same intellectual age. So a 10-year-old with ‘moderate’ intellectual disability, perhaps giving him a mental age of 4, did not recall things as well as a typically developing 4-year-old child.

This finding doesn’t mean that the evidence such children give is unreliable. Rather, it shows that knowledge of such disability is vital, in particular for determining whether to use a more nuanced style of questioning. All the children we interviewed responded more accurately to broad open-ended questions than to narrow, focussed questions and were able to provide relevant information in response to them. This was just as true for children with ‘moderate’ intellectual disabilities, but they struggled to provide fuller information. Having clear knowledge of their intellectual abilities would help interviewers to know the level of structured prompts that this group requires at particular points to elicit the most—and the most accurate—information.

Investigators should know mental age of child witness

Our research expands knowledge on the reliability of childhood testimony, studies of which have tended to focus on children with mainstream abilities. It tells us that investigators can have the same level of confidence in children with mild intellectual disabilities as they do in children who don’t have a disability, provided they know the mental age of the child and act accordingly. Conveying this knowledge would be inexpensive and wouldn’t require a lot of training. Doing so would be a highly cost effective policy shift that could be enacted relatively easily and offer enhanced legal protection to a vulnerable group of children.


 Brown DA, Lewis CN & Lamb ME (2015), Preserving the past: An early interview improves delayed event memory in children with intellectual disabilities, Child Development, 86.4

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