12 Intellectual disability12.4 Clinical
12.4 Offenders with intellectual disability
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Written by Resident Doctor Committee · Published
Who reaches the justice system
Offending is concentrated among people with borderline or mild intellectual disability, who reach the justice system far more often than those with moderate, severe or profound disability.
In moderate, severe or profound disability, carers and services manage challenging behaviour rather than prosecuting it.
Milder disability may go undetected in custody.
Prevalence in prison
Figures vary because studies measure different things: diagnosis needs intellectual and adaptive impairment beginning in development, whereas screens and intelligence test cut-offs do not.
Method | Reported figure |
|---|---|
Psychiatric assessment, ten international prison surveys | Typically 0.5 to 1.5% |
Screening in prisons and custody suites | About 5 to 7% |
The Learning Disability Screening Questionnaire reported sensitivity around 91% and specificity around 92%, and a positive result needs follow-up rather than counting as a diagnosis.
Unreliable accounts
Process | What it is |
|---|---|
Acquiescence | Agreeing regardless of content |
Yield | Accepting a leading suggestion |
Shift | Changing answers after negative feedback |
Compliance | Agreeing despite private disagreement |
Confabulation | Filling memory gaps with plausible detail, without deliberate deception |
Yield and shift contribute to interrogative suggestibility.
Understanding of a caution is checked through accessible explanation and demonstration, not a simple "Do you understand?". Repeating the exact words does not show comprehension.
Police custody
PACE Code C (Police and Criminal Evidence Act) defines vulnerability functionally, so suspected vulnerability triggers safeguards without waiting for a diagnosis.
The appropriate adult supports communication and safeguards fairness but does not replace a solicitor or interpreter.
Mental Health Act 1983
Where learning disability alone is relied on, specified powers require associated abnormally aggressive or seriously irresponsible conduct, but this does not apply to section 2 in the same way.
Treatment and release
Offence-related treatment is adapted, not withheld: slower pace, repetition, concrete examples and role play.
Small studies of adapted sexual offending treatment report improvements in knowledge, empathy or distorted beliefs, but these do not prove reduced reoffending.
Section 117 aftercare applies after qualifying hospital sections (3, 37, 45A, 47, 48), not after ordinary prison release.