Criminal Law Essay on Insanity

The defences of insanity, substantial impairment by abnormality of mind and automatism play a vital role in avoiding criminal liability. Principally, the defences reflect the idea that intellectually challenged individuals should not be penalised but rather treated of their mental impairment. However the outcomes of each defence have also been criticised as ‘anomalous and arbitrary’ due to conflicting legal and medical definitions. Consequently, support for the abolishment of these defences has been proposed to be replaced by sentencing discretion so that consistent and proportionate application of the law is achieved. However ultimately, abolishing the defences is undesirable as it is both ineffective and morally wrong to punish the mentally ill through sentencing. Rather, these defences need to be defined more clearly to curtail anomalous outcomes. The first half of this essay shall focus on key drawbacks of these defences in regards to judicial and medical interpretation as well as the role that sentencing plays in the class of the intellectually challenged. The second half shall assess reforms seeking to qualify and to abolish the defences altogether.

Problems Arising from Broad Definitions of Mental Incapacity Defences
Generally, the law acknowledges that mentally incapacitated offenders should not be treated in the same way as offenders of rational intelligence. Insanity is defined by the M’Naghten Rules as a ‘defect of reason’ caused by ‘disease of the mind’. However this classification of insanity has been criticised for being too broad often making it difficult to contrast from automatism. Automatism, described by Lord Goddard as akin to a novus actus interveniens causing involuntarily muscle movement, theoretically differs from insanity in two major instances. It is characterised by:
1. aetiology of an external kind (the ‘internal’/’external’ test)
2. minimal likelihood of recurrence
However in practice, the ‘internal’/’external’ test is a

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