[Forensic psychiatric examinations of the mentally retarded]

3,343 forensic psychiatric examinations were recorded in Norway from 1980 to 1996. 294 patients were diagnosed as mentally retarded. The annual number of mentally retarded persons increased during the observation period, but the relative percentage remained stable. The majority of the retarded persons being discussed had been charged with sexual felony, and some with arson. About half had previous convictions. Few had problems with alcohol or other intoxicants. Every fourth retarded person examined was considered not only to be mentally retarded, but also to suffer from other psychiatric disorders. We discuss to what extent deinstitutionalization of retarded persons and the accompanying social isolation they experience could contribute to the increase in maladaption and criminal behaviour. It is stressed that many of the sexual felonies may be explained by the fact that the mentally retarded are mentally immature.