Introduction: General Themes, Reform, Chapter Outlines

Chapter 1
Introduction: General Themes, Reform, Chapter Outlines

General themes

This book is concerned with the operation of the common-law defence of insanity and the related doctrine of automatism. In particular the book will focus on providing a consistent and principled approach to the reform of the insanity defence and the doctrine of automatism. In order to achieve this, the book will explore the appropriate boundaries of each of these in turn.

The defence of insanity and the doctrine of automatism each raise concerns reflecting their individual spheres of operation and development. The first part of this Introduction will outline several of the concerns relating to the defence of insanity and automatism individually. The second part of the Introduction will then indicate the broad issues to be considered, as well as the competing demands which must be balanced, by any reform proposal. The final part of the Introduction will provide an outline of the scope of each chapter in respect to both the general themes addressed and the options for reform discussed.

It will be argued that by including a volitional limb in the common-law defence of insanity, by using a refined notion of meta-responsibility in relation to drug-associated psychosis, and by introducing a new defence of impaired consciousness, a more consistent and principled approach to mental state defences may be achieved.


Chapter 2 outlines the elements of the common-law defence of insanity which arose from the rules established in M’Naghten’s case in 1843.1 In brief, for an accused to be afforded a defence, he or she must have experienced a ‘defect of reason’ arising from a ‘disease of the mind’ which affected his or her ability to know the nature and quality of the criminal act or that it was wrong. Some Australian jurisdictions now also include an added component of the effect of a disease of the mind on the ability or capacity to control the accused’s conduct.

The expressions ‘disease of the mind’, ‘mental disease’ or some other statutory variant are used to describe those internal conditions recognized by the law which, when resulting in a relevant incapacity, will give rise to the defence of insanity. Hence, a preliminary question which arises in the context of the defence of insanity concerns clarifying which states of mental malfunctioning will constitute a disease of the mind. One aspect of this question involves determining the degree to which a disease of the mind should reflect the medical notion of mental disorder. As will be outlined in Chapter 3, two approaches have been adopted in respect of this issue. Some jurisdictions have interpreted the expression consistently with clinical conceptions of mental disorder, thereby giving prominence to expert psychiatric evidence. Other jurisdictions however have chosen to incorporate judicial pronouncements into their definition, thereby asserting the normative and policy-driven nature of the enquiry.

A second question which arises in the context of the insanity defence concerns determining what types of incapacity should be allowed to ground the defence. On current formulations of the defence at common law a disease of the mind must give rise to a ‘defect of reason’ in order for the defence to be established. Such a ‘defect of reason’ is conventionally understood as a defect in an individual’s capacity for rational thought. As a result of such an interpretation, volitional defects which are not symptomatic of a state of cognitive defect will not be recognized as sufficiently incapacitating for the purposes of the defence. As will be discussed in Chapter 2, the ‘cognitive bias’ on the part of the common law has come to be viewed as overly restrictive in failing to take into account a variety of mental disorders. Chapter 5 will argue in support of the inclusion of an independent volitional limb to operate alongside the M’Naghten rules. Such a defence of ‘volitional insanity’ will operate to exempt an individual from criminal responsibility where he or she cannot control his or her conduct, even where he or she knows the nature, quality and wrongness of his or her conduct.


As will be discussed in Chapter 2, the doctrine of automatism has come to be understood as involving those mental conditions that cause an individual to act in an involuntary fashion. A distinction is drawn between those states which go to the question of an accused’s involuntariness (’sane’ automatism) and those states of involuntariness which are due to the effects of a disease of the mind (’insane’ automatism). While sane automatism will result in an outright acquittal, insane automatism will generally result in the accused being detained in a secure hospital and subjected to a therapeutic regime.

Given the different outcomes there is a strong incentive for an accused to raise evidence of sane automatism. However, in the absence of a reliable means of identifying the precise cause of an accused’s state of mental malfunction, a principal concern with states of automatism is their susceptibility to abuse. Such a concern is particularly acute in the context of ‘psychological-blow’ automatism involving severe psychological trauma leading to a dissociative state.

One particular feature of cases where psychological-blow automatism has been pleaded is that the conduct in such cases has been characterized by motivated, goal-directed behaviour. Expert evidence is divided in respect of whether or not such behaviour may be characterized as involuntary. Consequently, in such cases there is a concern that there will be a failure to convict where appropriate and not acquit where such acquittals are warranted. In order to foreclose such an outcome, Chapter 6 will argue for the introduction of a new defence of ‘impaired consciousness’. The new defence of impaired consciousness will require individuals who claim to have experienced a state of dissociation arising from a psychological blow to satisfy certain normative conditions before they are excused.

Options for reform

In considering reform proposals in respect of the defence of insanity and the doctrine of automatism, several competing factors must be taken into account. One such factor involves ensuring that the scope of the defence of insanity and automatism is not drawn too broadly so as to exempt from responsibility those individuals who, while rational, choose to engage in criminal conduct. As such individuals are able to distinguish between right and wrong and able to control their conduct, they are fit subjects of the criminal law. Chapter 4

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