Homicide due to mental disorder

The article by Large et al describes the rise and fall in homicides attributed to mental disorders in England and Wales over the past 50 years. ¹ Since 2000, the rate of homicide due to a mental disorder in England and Wales has been 0.07 per 100 000 or lower. Encouraged by the authors, we examined the rate of homicides due to a mental disorder in The Netherlands. Dutch law considers responsibility for crimes to be diminished if there is a causal relationship between a mental disorder and the crime committed. Five degrees of responsibility are defined (i.e. complete responsibility, slightly diminished, diminished, considerably diminished, and total absence of responsibility). A severe psychiatric disorder, usually of a psychotic nature, is a necessary condition for a ‘total absence of responsibility’ finding.

From 1212 cases of homicide between 1 January 2000 and 31 December 2006, 1020 (84.2%) defendants were psychiatrically assessed pre-trial. Of these, 58 (5.7%) were considered to have total absence of responsibility. Furthermore, 63 (6.2%) were found to have considerably diminished responsibility, 239 (23.4%) diminished responsibility, 309 (30.3%) slightly diminished responsibility, and 259 (25.4%) complete responsibility. A psychotic disorder was diagnosed in 115 (11.3%) people, which is in line with earlier studies. ² The rate of homicide due to mental disorder would be 0.11 per 100 000 when individuals with a total absence of or strongly diminished responsibility are included. If individuals with a diminished responsibility are also included, this would be 0.32 per 100 000.

The difference between England and Wales and The Netherlands may be explained by a different view on the issues of a diminished responsibility. ³ This may also explain the rise and fall of homicides due to mental disorders in England and Wales over the past 50 years.