A National Survey of Offending Behaviour amongst Intellectually Disabled Users of Mental Health Services in Ireland


Persons with an Intellectual Disability have been shown to be overrepresented within the Criminal Justice System. This applies to the setting of police custody[1], [2] where police officers have been shown to have poor skills in recognising mental disorder and Intellectual Disability[3]

The UK Police & Criminal Evidence Act of 1984 (PACE) provides for the nomination of a “responsible adult“ for “vulnerable suspects” but equivalent Irish Regulations are not so well developed[4] and so constitutes an absence of appropriate safeguards for persons with an Intellectual Disability who come in contact with the Criminal Justice System.

Murphy et al[5] reported from a sample of 10% of the Irish prison population that as many as 28.8 % of Irish prisoners may have a Learning Disability as measured using the Kaufmann Brief Intelligence test, Wide range achievement test and the vocabulary subtest of the Weschler Adult Intelligence test –revised.

Issues of capacity also complicate the application of a legal paradigm to problem behaviours. The overlap between offending behaviour and “challenging behaviour“ as described by Emerson[6] means that much offending behaviour goes unreported. This phenomenon has been well described by Lyall [7] and is encapsulated by the comment that “staff at one residential home said they would hesitate to report rape”.

Simpson et al[8] conclude their Systematic Review of the evidence regarding the association between Intellectual Disability and offending, by commenting that there is “no clear evidence that the prevalence of offending among people with a Learning Disability is higher than for the wider population… offending among those with an IQ less than 50 is rare”.

Holland[9] has reported that of those persons with an LD who offend, young males are over-represented.

To date no previous study has been untaken to estimate the level of offending behaviour amongst service users of Irish mental health services who have an Intellectual Disability.

The Forensic Learning Disability Working Group of the Irish College of Psychiatrists was established in order to establish the level of need for a Forensic Learning Disability service in Ireland and develop a College position paper. A national survey was undertaken in order to inform the conclusions and recommendations which were subsequently set out in the position paper People with a learning disability who offend: forgiven but forgotten ?[10].

A National Survey of Offending Behaviour amongst Intellectually Disabled Users of Mental Health Services in Ireland


The items of data measured comprised demographic details such as gender and age range ( 18-25 years, 25-55 years, 55 years and over). For each subject a level of disability was requested and this was defined as per DSM-IV[11] criteria for mental retardation.

An explanatory note was also included in the postal survey stating that target behaviour was behaviour of such severity that in the absence of a learning disability criminal proceedings would ensue. The purpose of this approach was to capture all offending behaviour without reference to issues of an individual’s capacity or criminal intent . Catagories of offence were also defined:

Text Box 1: Offence Types

Offence Types

  • Offences against Property
  • Arson / Fire Setting
  • Criminal Damage
  • Larceny / Burglary
  • Car Theft / Joyriding
  • Offences against Person
  • Drug / Alcohol Related Offences
  • Assault / Battery
  • Manslaughter
  • Murder
  • Indecent Exposure
  • Stalking / Dangerous Threatening Behaviour
  • Sexual Assault on a Child
  • Sexual Assault on an Adult
  • Prostitution / Soliciting

A postal survey was undertaken targeting the lead clinicians of all Intellectual Disability Psychiatry , General Adult Psychiatry and Forensic Psychiatry Services in the Republic of Ireland. A second mail shot was sent out 6 weeks prior to the closing date for receipt of responses.

This survey requested anonymous data on service users with an Intellectual disability and offending behaviour.


Response rate:

  • Of the original 52 services contacted 28 responded giving an overall
  • Response rate of 56%.
  • The response rate was best for the Intellectual Disability Sector (93%)
  • and worst for the General Adult Psychiatry Services (33%).
  • There was a 100 % response rate from the Irish National Forensic
  • Mental Health service.

Service user characteristics

Overall data relating to 431 service users nationally was returned. 349 service users (81%) were male and 82 ( 19%) were female. The vast majority of service users were aged 25-54years( 73.8%), followed by those aged 18-24 years ( 17.6%) . Those aged 55years and over only constituted 8.6% of our sample. The most overrepresented group in our sample were those reported to have an IQ in the severe range ( 45%) , while those with an IQ in the moderate range constituted 41.3% and those in the mild range were in a minority of only 13.7%

Offence Types

The most frequent offence type was assault ( 37.4%) followed by indecent exposure ( 13.7%). All offences and their frequencies are illustrated in Table 1

Table 1

Offence Type






Indecent Exposure



Threatening behaviour/Stalking



Criminal damage



Sexual assault on an adult



Sexual assault on a child



Larceny/ burglary






Drug related






Car theft/ joyriding












Serious offences

82 extremely serious offences were reported ( 5 instances of unlawful killing , 28 instances of sexual assault on an adult , 27 instances of sexual assault on a child and 22 instances of firesetting/Arson) . Only 3 subjects of this study who come within this category were located within the Irish Forensic mental health services and consequently the vast majority of service users presenting with these severe offending behaviours are being managed within either Intellectual Disability Services or General Adult Psychiatry Services.

In summary , males were massively overrepresented in relation to all serious offence types. Those aged 25-54 was massively overrepresented in relation to all severe offence types, except for unlawful killing for which no age range clearly predominated.

In relation to level of Disability, unlawful killing was predominantly ascribed to subjects in the moderate range, as was sexual assault on an adult. Those in the severe range were overrepresented in relation to sex offending on a child. No level of disability predominated in relation to fire-setting / arson .

Service users urgently requiring Forensic LD

Responses to our survey yielded a total of 90 individuals for whom service providers stated there was an urgent need for a National Forensic Learning Disability service.


The results of this survey indicate that there is a significant population of 431 service users with an Intellectual disability who present with behavioural problems which service providers catagorise as “offending”. This constitutes a massive unmet need in the absence of a Forensic Learning Disability Service in Ireland.

In addition, service providers have highlighted 90 service users whom they deem to be in urgent need of a Forensic Learning Disability Service.

The demographic characteristics of our sample population resemble those of other forensic populations with an Intellectual disability which have reported by Holland[12] as predominantly young and of male gender.

The level of disability of our study sample reflects the population of persons attending Intellectual Disability services in Ireland and is predominantly constituted by persons in the moderate or severe range.

Although greater degrees of disability will likely correlate with a diminished likelihood of culpability, offending behaviours still require a clinical response in the absence of access to a criminal justice process.

We consider that those offenders in the mild range may either be attending General Adult Psychiatry services for which our survey response rate was poor. In addition is is likely that the majority of offenders with a mild Intellectual Disability may in fact be found within the Irish prison service.

Of this study population , a minority of 82 service users are reported to have a record of extremely serious offending behaviour( e.g. unlawful killing, sexual assault , arson). The demographic characteristics of this group resemble the overall study population . As only 3 of these services users were reported to be in the care of the National Forensic Mental Health Service the vast majority of this population is presenting with a clinical risk which is being managed without ongoing expert input from forensic services and in settings where a most vulnerable peer group is potentially exposed to grave harm.


It is recognised internationally that service development for offenders with an Intellectual Disability is hampered by the tendency for this population to “ fall between stools “ in relation to placement within programmes and dedicated revenue streams[13].

It is welcome that A Vision for Change[14], the current Irish Mental Health Policy has for the first time acknowledge the need for an Irish Forensic Learning Disability Service but only recommends the provision of one 10 bedded inpatient unit for the whole of the republic of Ireland

Day[15] has recommended that an adequate sub-regional service would require 30 (medium secure) beds for Intellectually Disabled offenders per 500,000 population. The Irish Department of Health in 1996 suggested 3 regional 10 bedded units would be adequate[16].

Recommendations from the Irish National Disability Authority in 2003 favoured 4 regional units affiliated to the Irish National Forensic Mental Health Services[17].

We reiterate the recommendations contained in the recent Irish College of Psychiatrists document People with a Learning Disability who offend: forgiven but forgotten ?[18]

In summary , we consider that the development of a Forensic Learning Disability Service for the Republic of Ireland should be actioned as a matter of priority and in keeping with stated government mental health policy.

We also recommend that such a service should be delivered by fully resourced multidisciplinary teams across settings of varying therapeutic security ( from high to low and community environments).

Specifically Two 30 bedded inpatient units would be a minimum initial requirement in addition to dedicated step-down community residential facilities to prevent silting of the service.

Court Diversion schemes similar to those in place for mentally disordered offenders[19] should also be developed.

In order to progress the development of an Irish National Forensic Learning Disability Service multi-agency collaboration will be required between relevant Government Departments and chief stakeholders within the Irish Health Service, Healthcare professions, Prison service, Criminal Justice Service and organisations representing key stakeholders.

[1] Lund, J. (1990) Mentally retarded criminal offenders in Denmark. British Journal of Psychiatry, 156, 726-731

[2] Gudjonsson G.H., Clare I.C., Rutter S et al. (1993) Persons at Risk during Interview in Police Custody: the Identification of Vulnerabilities . ( Royal Commission on Criminal Justice Research study No. 12 ) London HMSO,

[3] Lyall, I. Holland, A.J., Collins ,S. et al. (1995) Incidence of persons with a learning disability detained in police custody: a needs assessment for service development. Medicine , Science and the Law, 35, 61-71.

[4] Criminal Justice Act, 1984 ( Treatment of Persons in Custody in Garda Siochana Stations ) Regulations 1987.

Law Reform.

[6] Emerson, E. (1995) Challenging Behaviour: Analysis and Intervention in people with Learning Disabilities. Cambridge University Press, Cambridge.

[7] Lyall, I., Holland, A., Collins, S. Offending by adults with learning disabilities and the attitudes of staff to offending behaviour: implications for service development. Journal of Intellectual Disability Research. Dec 1995. 39 (6) 501-508

[8] Simpson, M. & Hogg, J. (2001) Patterns of offending among people with Intellectual Disability: a Systematic Review. JIDR, 44, 384-396

[9] Holland, T., Clare, I., Mukhopadhyay, T. Prevalence of “criminal offending” by men and women with intellectual disability and the characteristics of “offenders”: implications for research and service development. Journal of Intellectual Disability Research May 2002, 46 (supplement 1) 6-20

[10] Irish College of Psychiatrists (2007) Persons with a Learning Disability who offend: forgiven but forgotten ? ( OP63)

[11] American Psychiatric Association. DSM-IV Diagnostic And Statistical Manual of Mental Disorders. Fourth Edition Text Revision

[12] Holland, T., Clare, I., Mukhopadhyay, T. Prevalence of “criminal offending” by men and women with intellectual disability and the characteristics of “offenders”: implications for research and service development. Journal of Intellectual Disability Research May 2002, 46 (supplement 1) 6-20

[13] Myers, F. (2004) On the Borderline? People with Learning Disabilities and/ or Autism Spectrum Disorders in Secure, Forensic and other Specialist settings. Scottish Development Centre for Mental Health.

[14] Department of Health and Children (2006) A Vision for Change. Report of the Expert Group on Mental Health Policy

[15] Day K. Mental health services for people with mental retardation: a framework for the future. Journal of Intellectual Disability Research 1993 37 7-17

[16] Department of Health.(1996) Discussion Document on Mental Health Needs of Persons With Mental Handicap .Dept of Health, Hawkins House, Dublin 2. Irish Department of Health 1996

[17] National Disability Authority (Ireland) 2003.Review of Access to Mental Health Services for People with Intellectual Disabilities

[18] Irish College of Psychiatrists (2007) Persons with a Learning Disability who offend: forgiven but forgotten ? ( OP63)

[19] O’Neill, C Liaison between criminal justice and psychiatric systems: Diversion services. Irish Journal of Psychological Medicine 2006 ; 23(3): 87-88