Involuntary Conduct: Defence of Impaired Consciousness

Chapter 6
Involuntary Conduct: Defence of Impaired Consciousness

Introduction

It was noted in the previous chapter that the importance of voluntariness to criminal liability is recognized in both common law and code jurisdictions.¹ All criminal offences require proof of a physical element or actus reus. The physical element must be performed voluntarily. Conduct is only voluntary where it is the product of the will of the person performing the conduct.² A person is not criminally responsible for conduct which occurs independently of the exercise of his or her will.³ The requirement that an accused’s conduct be the result of the exercise of his or her will has been interpreted to be the same as the requirement that conduct be voluntary.⁴ On the above analysis, the absence of voluntariness means that while the actus reus or physical element of the offence may be established (for example, the accused shot the victim), the accused may avoid criminal liability on the basis that he or she did not will the prohibited act (for example, the shooting was the result of a spasm or impaired consciousness).

Traditionally two varieties of states of involuntariness are distinguished: those which do not involve some form of impaired consciousness and those which do involve a state of impaired consciousness. Cases involving behaviour arising from a reflex response, bodily spasm and convulsions do not arise as a result of a state of impaired consciousness. However, some claims of involuntary conduct arise from causes involving a state of impaired consciousness. Such states include concussion caused from a blow to the head,⁵ the consumption of alcohol or drugs,⁶ hypoglycaemia⁷ and epilepsy.⁸ Further, the High Court in R v Falconer⁹ has held that an emotionally traumatic event (a ‘psychological blow’) may produce an extraordinary degree of stress so as to result in a state of dissociation.¹⁰ A state of involuntary conduct arising from some form of impaired consciousness is referred to as automatism.¹¹

A distinction is drawn between two varieties of automatism depending on whether the condition suffered by the accused is a form of mental disorder. Where the state of impaired consciousness resulting in involuntariness stems from some form of mental disorder such a state is referred to as ‘insane automatism’. Where however, the state of impaired consciousness resulting in involuntariness does not arise from some form of mental disorder such a state is referred to as ‘sane automatism’. This chapter will be concerned with states of sane automatism.

Arranged schematically the above taxonomy may be figured as follows:

Figure 6.1 Traditional taxonomy of conduct

As discussed in Chapter 2, different procedural and dispositional issues arise depending on whether a state of impaired consciousness is characterized as arising from a disease of the mind or not. In the context of conduct arising from a disease of the mind at common law, where such conduct is not voluntary, it will at best give rise to a defence of mental impairment: it will not result in an outright acquittal.¹² As discussed in Chapter 5, notwithstanding the involuntary nature of such conduct, social-defence considerations require an accused to plead the defence of mental impairment and receive the special verdict rather than obtain an outright acquittal. As a result, Chapter 5 argued for the recognition at common law of an independent volitional limb to the defence of mental impairment. While such a limb would continue to recognize social-defence considerations, it would dispense with the current requirement that an accused raise evidence that his or her volitional impairment is symptomatic of a cognitive defect. Where, however, an accused’s involuntary behaviour does not arise from a disease of the mind, then an accused is entitled to an acquittal as a pre-condition of criminal responsibility, that is, voluntariness, is not satisfied.

Before proceeding it may be noted that the Criminal Codes of Queensland and Western Australia which are based on the Griffith Code take a fundamentally different approach to the common law. Unlike the common law, the Griffith Code does not conceptualise voluntariness as part of the physical element or actus reus of the offence. The concepts of actus reus and mens rea are not used in the Queensland and Western Australian Codes.¹³ In Queensland and Western Australia a lack of will operates as a defence, it being found in the Queensland and Western Australian Codes in ‘Chapter 5-Criminal Responsibility’, and ‘Chapter V-Criminal Responsibility’ respectively, alongside other factors which operate to negate criminal responsibility such as mistake, emergency and duress. This chapter will not be concerned with these Code States but will focus on altering the common law approach to the question of voluntariness as an aspect of the physical element of an offence. A consequence of the change sought to be made will be to bring the common law approach more in line with the current Griffith Code approach to voluntariness as an excuse.

Behaviour arising from a reflex response, bodily spasm or convulsion has been viewed as being an uncontroversial instance of involuntariness.¹⁴ In such situations, quite clearly, an accused’s bodily movements are not the result of an exercise of will on his or her part but are produced by some other agency. However, instances which are more problematic are those where the alleged lack of voluntariness stems from a mental state. In particular, the extension of the doctrine of sane automatism to cases of dissociation arising from psychological-blow automatism has been viewed as problematic in several respects.¹⁵

In order to meet the challenge posed by such problematic cases this chapter will argue for moving the voluntariness requirement for instances other than reflex, spasm and convulsion from the actus reus or physical element of an offence to a defence structure akin to that found in the Griffith Code. Hence, it will be argued that claims of involuntariness arising from a state of impaired consciousness which do not arise from a disease of the mind should be treated as excuses. That is, rather than being viewed as it currently is in the common law as relevant to the actus reus, or physical element of an offence, it will be argued that an instance of sane automatism is best viewed as operating as it does in the Griffith Code, as an excuse.

The chapter will begin with an outline of the operation of excuses, showing a necessary condition of such excuses and the degree to which certain criminal-law defences satisfy such a condition. This will be followed by an analysis of the voluntariness requirement in the criminal law. The analysis will distinguish between involuntary movements which are the result of bodily spasms and reflex actions and those states of volitional impairment which are the result of a state of impaired consciousness (sane automatism). It will then be indicated why claims of sane automatism should be viewed in terms of an excusatory defence rather than as an aspect of the actus reus of an offence. Succinctly stated, by viewing sane automatism as a defence, claims of volitional impairment arising from a state of impaired consciousness will be required to satisfy an objective condition as is demanded of other excuses in the criminal law. Before proceeding to formulate the proposed partial defence of impaired consciousness, this section will note and respond to the claim that removing sane automatism from the actus reus of the offence and viewing it as a defence would be unfair to an accused seeking an outright acquittal. Following on from this, the next section will formulate and describe the proposed partial defence of impaired consciousness. The defence of impaired consciousness aims to ensure that claims of volitional impairment are subject to the same restrictions as other excuse conditions in the criminal law. The final substantive matter which will be considered is a suggestion calling for the subsuming of states of involuntariness under a broad mental-disorder defence. It will be argued that such an approach should be rejected in favour of using the defence of impaired consciousness in order to distinguish between those varieties of impaired consciousness which arise from a disease of the mind and those which do not. The conclusion will provide an overview of the results of the analysis.

A working theory of excuses

Several distinctions may be drawn amongst the extant varieties of substantive, as distinct from procedural, criminal-law defences.¹⁶ One distinction which may be drawn in the classification of criminal-law defences is that between ‘justifications’ and ‘excuses’.¹⁷ Justifications involve conduct which is morally warranted, that is, conduct which is not considered to be wrong.¹⁸ A paradigmatic instance of justification is self-defence: the defence of self or other from unlawful attack being considered to be morally warranted conduct under all circumstances. An excuse represents a legal conclusion that the conduct is wrong, undesirable, ought not to be tolerated and should be avoided in the future, even in the same situation.¹⁹ However, criminal liability is reduced in cases of excuse because while the conduct is wrong for one reason or another the accused’s blameworthiness is mitigated. That is, excuses are applied to those instances where, while an accused’s conduct is wrong, there is some reason for which he or she is not held fully responsible.

As will be outlined below, the reasons for which an accused’s blameworthiness is reduced will differ from one excuse to another. It has been held that as there are no formal dispositional consequences arising from the distinction between justifications and excuses, the distinction is of little practical significance in Australian law.²⁰ However, the distinction between excuses and justifications remains important in terms of the analysis of complex moral situations.²¹ References to criminal-law defences in this chapter will be taken to refer to excuses as the conduct engaged in by an accused wishing to raise evidence of involuntariness will not involve conduct which is morally warranted. If such conduct was justified there would be no need for an accused to raise evidence of involuntariness, as he or she could rely on an outright acquittal on the basis of a justificatory defence. My concern in this chapter is with the provision of excuses to those accused that because of a mental, emotional or physical condition experience a state of impaired consciousness resulting in volitionally impaired conduct.

An accused will be allowed to raise an excuse if and when it is judged that even someone well equipped with rational powers (of self-control, foresight and so on) would have behaved in a similar fashion in the circumstances. That is, in order to judge whether an accused is deserving of an excuse, the law introduces an objective standard into excuse formulations so as to allow an accused’s behaviour to be assessed against such a standard. In principle, modern excuses hold an accused to some form of objective standard in judging his or her efforts. For example, in the context of the defence of duress, current excuse formulations require that an accused’s capacity to resist be sufficiently impaired that he or she could not reasonably have been expected to have avoided the offence.²² The law’s willingness to excuse an accused under such conditions reflects a normative judgment in respect of the adequacy of his or her effort to resist. Several excuses have explicit objective standards as part of their criteria,²³ while others have broad criteria that invite a general normative assessment by the jury and, in this fashion, introduce what is essentially an objective standard.²⁴ The operation of this normative judgment, or objective standard, in respect of several defences will be considered below.

A further distinction which may be drawn amongst criminal-law defences is that between those defences which deny a necessary element of an offence, such as the physical (actus reus) or fault (mens rea) element (‘failures of proof’), and those defences which operate subsequent to the establishment of the requisite elements of the offence (‘excuses’). Failures of proof are raised in order to show that, as an element of the criminal offence has not been proved, there is no case for which the accused must answer. Technically, where an accused raises evidence that an element of the offence has not been established, he or she may avoid liability given that he or she has not committed the requisite elements of a criminal offence. Consequently, in such a situation, rather than raising a true defence, the accused claims that there is a failure of proof in respect of a necessary element of the offence. For example the failure of the prosecution to prove the occurrence of voluntary conduct beyond reasonable doubt will result in an outright acquittal.²⁵ Similarly, mental disorder falling short of insanity may be used to show that the element of specific intention has not been established.²⁶ In the latter case, an accused will not be held liable for an offence which requires proof of specific intent.²⁷ Where however, the elements of the offence have been established, an accused may seek to mitigate his or her blameworthiness by raising an excuse. In such a case the accused will seek to show that he or she should be provided with an excuse in the light of mitigating factors. For example, the defence of duress operates subsequent to the prosecution having established that the accused voluntarily performed the relevant criminal conduct with the necessary intent albeit under constrained circumstances.²⁸

One of the features distinguishing excuses from failures of proof is that the underlying normative element to excuses is lacking in pure failure of proof claims.²⁹ The ascription of praise or blame to an accused raising an excusatory defence will be determined according to whether his or her behaviour accords with the normative element, or objective standard, underlying the excuse. Such a normative element tells us when an accused’s action is clearly inexcusable. There are some actions that are inexcusable under particular excuses and therefore should not be done. For example, in certain jurisdictions duress will not excuse an act of murder, and where such an act is committed the defence will not be allowed to be raised.³⁰ In contrast, as voluntariness is an aspect of the physical element of an offence, a denial of voluntariness will constitute a failure of proof. As a failure of proof the application of the voluntariness requirement to particular offences is not determined by a normative element.³¹ Hence, a claim of lack of voluntariness will constitute a failure of proof in respect of all offences.³²

The above section has detailed a particular condition which must be satisfied before an excusatory defence is recognized in the criminal law. As noted an excuse will be available to an accused who for some reason evinces a degree of impairment considered sufficient, when assessed against an objective standard, to reduce his or her blameworthiness. Unlike the case of a failure of proof defence, the application of an excusatory defence will be determined on the basis of an objective standard or, normative element. The normative element underlying the excuse will indicate those instances when an accused’s action is inexcusable. I turn now to a consideration of the degree to which various criminal law defences comply with the above condition of excuses.

Substantive defences

This section will outline the operation of an objective standard in the context of several defences. The defences of duress and provocation will be considered as examples of defences which have explicit objective standards as part of their criteria. The partial defence of diminished responsibility will be used in order to show how the use of broad criteria in an excusatory defence may invite a general normative assessment by the jury and, in this fashion, introduce what is essentially an objective standard. In order to further refine the discussion of excusatory defences both the insanity defence and the doctrine of doli incapax will be presented by way of contrast as instances of a defence resulting in an accused being rendered exempt from criminal responsibility.

Duress The defence of duress excuses criminal behaviour where such behaviour arises in circumstances where the fear of violence induces the accused to commit the crime.³³ The defence has been defined as arising

where the accused has been required to do the act charged against him (i) under a threat that death or grievous bodily harm will be inflicted unlawfully upon a human being if the accused fails to do the act and (ii) the circumstances were such that a person of ordinary firmness would have been likely to yield to the threat in the way the accused did and (iii) the threat was present and continuing, imminent and impending and (iv) the accused reasonably apprehended that the threat would be carried out and (v) he was induced thereby to commit the crime charged and (vi) that the crime was not murder, nor any other crime so heinous as to be excepted from the doctrine and (vii) the accused did not, by fault on his part when free from the duress, expose himself to its application and (viii) he had no means, with safety to himself, of preventing the execution of the threat, then the accused, in such circumstances at least, has a defence of duress.³⁴

The defence is recognized as having three requirements: (1) there must have been a threat made by another against the accused if he or she does not perform the criminal offence (the nature of the threat requirement), (2) the threat must have induced the accused to commit the crime (the subjective test) and (3) the threat was such that it might have caused an ordinary person in the accused’s position to also have committed the offence (the objective test).³⁵

The fact that an accused was induced to commit a crime because of a threat does not negate either the physical element (actus reus) or the fault element (mens rea) of the offence. The defence implies that the accused has deliberately chosen to commit the criminal offence. Unlike physical compulsion which negates an accused’s will the defence of duress does not deny the voluntariness of an accused’s action.³⁶ Because of a threat, the accused is forced to engage in conduct, which he or she would not, under normal circumstances, engage in.

While many crimes are committed under various sorts of pressure, that which distinguishes duress as a defence is that the crime committed by the accused is a reasonable response to the threat in circumstances arising through no fault of his or hers. Hence, an accused individual must hold a well-grounded fear of death or grievous bodily harm arising from the conduct of the party making the threats.³⁷ Equally however the defence will arise only when it is judged that even someone well equipped with rational powers (of self-control, foresight and so on) might also have acted in that way under like circumstances. As stated by Hunt J in Abusafiah:

The Crown must establish in relation to any such threat which may reasonably have been made that there is no reasonable possibility that such was its gravity that a person of ordinary firmness of mind and will as the accused, would have yielded to the threat in the way the accused did.³⁸

To this end, the defence holds an actor to some form of objective standard in judging his or her efforts. An accused’s capacity to resist must be sufficiently impaired so that he or she could not reasonably have been expected to have avoided the offence. That is, in order for the defence of duress to operate, the accused must have the firmness of mind reasonably to be expected of an ordinary person in like circumstances. The objective element requires that the threat posed is of such gravity as might cause an ordinary person in the accused’s position to commit an offence.³⁹

A modern statutory formulation is to be found in section 9AG of the Victorian Crimes Act the relevant parts of which read:

9AG Duress

(2) A person carries out conduct under duress if and only if the person reasonably believes that –

(a) subject to subsection (3), a threat has been made that will be carried out unless an offence is committed; and

(b) carrying out the conduct is the only reasonable way that the threatened harm can be avoided; and

(c) the conduct is a reasonable response to the threat.

It will be noted that the Victorian formulation stipulates as a requirement of the defence that the accused’s belief in the threat is well-founded (‘reasonably believes’), acting on the threat was ‘the only reasonable way’ of avoiding the threatened harm and that the conduct engaged in was a ‘reasonable response’. Hence, the Victorian statute makes explicit the objective element against which an accused’s conduct will be assessed by requiring that both the carrying out of the conduct and the nature of the accused’s conduct were reasonable.

Provocation Another defence revealing an explicit use of an objective standard is the defence of provocation.⁴⁰ As a substantive partial defence, the successful operation of the defence of provocation reduces an accused’s liability for murder to that of manslaughter. There are several elements to the substantive defence which must be satisfied before an accused will be partially excused: first, the accused must have killed the victim in circumstances recognized as provocative at law; secondly, the accused must because of the provocative circumstances have lost self-control; thirdly, that the provocation was sufficient to render an ordinary person to have lost control and form an intention to cause serious harm or death; and fourthly, while in such a state, the accused must have used retaliatory force before regaining control.⁴¹ In order to establish whether an ordinary person would have lost control under similar circumstances two questions are posed: (1) what is the gravity of the provocation faced by the agent? and (2) could provocation of that gravity cause an ordinary person to lose self-control and react as the agent did? However, while both questions are concerned with an objective standard, all of the characteristics of the defendant are relevant only to the first question.⁴² The only characteristic of the defendant relevant to the second question is his or her age.⁴³

Jeremy Horder has noted that the ordinary-person aspect of the defence is founded on what is termed the ‘objective-capacity’ theory of evaluating an accused’s blameworthiness.⁴⁴ On the objective-capacity theory, an accused’s blameworthiness will be determined according to whether or not his or her conduct met a ‘morally salient standard’.⁴⁵ Such a standard will be altered only to the degree to which it adequately reflects the age of the accused.⁴⁶ The requirement under the substantive defence that an ordinary person would have lost self-control was a historical development which resulted in the defence moving from being a partial justification to a partial excuse.⁴⁷ On the loss of self-control model the provoked response by an accused was no longer viewed as a rational response to being wronged by another. Rather, an accused’s blameworthiness was mitigated on the basis that the loss of self-control he or she experienced might also have occurred to an ordinary person in such circumstances.⁴⁸ While the above account describes the conventional rationalization of the defence there are, however, other models which have been proposed.

More recent formulations of the defence have suggested that provocation should be viewed in terms of an accused’s justified sense of being wronged.⁴⁹ In this latter formulation, in place of a requirement that an accused lose his or her self-control in circumstances in which an ordinary person might, the moral basis for mitigating the accused’s offence arises where ‘the defendant acts in response to gross provocation in the sense of words or conduct (or a combination) giving the defendant a justified sense of being severely wronged’.⁵⁰ As the United Kingdom Law Commission noted:

The preferred moral basis for recognizing the partial defence of provocation is that the defendant had legitimate ground to feel strongly aggrieved at the conduct of the person at whom his/her response was aimed, to the extent that it would be harsh to regard their moral culpability for reacting as they did in the same way as if it had been an unprovoked killing.⁵¹

On this proposed rationale for the defence, the issue of loss of self-control no longer plays a major role as an element of the defence.⁵² Rather, it is the gravity of the victim’s conduct and the accused’s justifiable sense of being wronged which will determine whether the offence should be mitigated from murder to manslaughter.

Similarly, the notion that provocation reduced an accused’s culpability given his or her loss of self-control was ultimately rejected by the VLRC, which recommended the abolition of the defence.⁵³ In its place the VLRC called for provocation along with other circumstances to be taken into account at sentencing. The VLRC argued that in order to determine an accused’s culpability in the context of provocation for sentencing purposes it was important to consider the reasons why a person killed. In this respect the commission noted that contemporary community standards demanded that individuals control their anger notwithstanding a degree of provocation.⁵⁴ Moreover, the VLRC cited empirical evidence indicating that the defence was applied in a gender-biased way with men raising the defence in the context of the deterioration of intimate relationships.⁵⁵ Graeme Coss has remarked that the use of the defence occurs in situations where ‘the real “loss of control” is that men have lost control of their women’.⁵⁶ The VLRC argued in their report that:

Emotion is not an uncontrollable irrational force. Instead our emotions embody judgments and ways of seeing the world for which we can and should be held to account. If we accept that emotions can be objectively assessed and judged, then arguably it is also possible to assess culpability based on people’s reasons for behaving (and the emotions underlying those reasons).⁵⁷

On a reasons-based approach to the question of an accused’s culpability, the reasons why a person killed may be analysed and evaluated. Such an approach focuses on the wrongfulness of the victim’s conduct and the justifiable nature of the accused’s retaliatory response. The act of the accused will be mitigated when the reasons for the accused’s anger are found to be good reasons even though the act of the accused in using lethal retaliatory force is not warranted.⁵⁸

The VLRC recommendations were ultimately accepted by the legislature and the partial defence subsequently abolished in Victoria.⁵⁹ Nevertheless, both the traditional interpretation of the substantive defence and the more recent rationalizations of the defence and its relationship to culpability involve an explicit acknowledgment of the objective aspect of the excusatory defence. The former, traditional approach emphasises the requirement that an accused’s loss of self-control be such that an ordinary person in like circumstances would react in a similar fashion. The latter rationale highlights the fact that the reasons for which an accused is justified in feeling aggrieved must be good reasons. The reasons for which an accused will be justified in feeling aggrieved will be good reasons, when the victim’s actions and/or words cause the accused to have ‘a justifiable sense of being seriously wronged’.⁶⁰ For the purpose of establishing the gravity of a victim’s provocative conduct and the justifiability of an accused’s aggrievement, a jury will be required to evaluate these issues against an objective morally salient standard.

Diminished responsibility The defence of diminished responsibility is a partial defence to murder which reduces the offence to a lesser form of culpable homicide. The rationale for the defence emanated from the view that certain states of cognitive or volitional impairment which were not recognized by the common-law defence of insanity were deserving of recognition in reducing an accused’s criminal responsibility. Further, the defence arose in response to the provision of mandatory death sentences for the crime of murder, which came to be viewed as unduly harsh. Diminished responsibility ameliorated the strictures of the law in what were felt to be deserving cases by recognizing a degree of cognitive or volitional impairment as mitigating an accused’s culpability and providing the accused with an alternative verdict of manslaughter.⁶¹

The defence was originally developed by the Scottish courts and found statutory expression in section 2(1) of the United Kingdom’s Homicide Act 1957:⁶²

Where a person kills or is a party to a killing of another, he shall not be convicted of murder if he was suffering from such abnormality of mind (whether arising from a condition of arrested or retarded development of mind or any inherent causes or induced by disease or injury) as substantially impaired his mental responsibility for the acts or omissions in doing or being a party to the killing.

The defence of diminished responsibility is only available in the Australian Capital Territory, New South Wales, the Northern Territory and Queensland.⁶³ A modern restatement of the partial defence is to be found in section 23A of the New South Wales Crimes Act,⁶⁴ the relevant parts of which read:

A person who would otherwise be guilty of murder is not to be convicted of murder if:

(a) at the time of the acts or omissions causing the death concerned, the person’s capacity to understand events, or to judge whether the person’s actions were right or wrong, or to control himself or herself, was substantially impaired by an abnormality of mind arising from an underlying condition, and

(b) the impairment was so substantial as to warrant liability for murder being reduced to manslaughter.

3. The ‘abnormality of mind’ must have substantially impaired the accused’s mental responsibility for the act or omission resulting in death.⁶⁵

The issue of whether the above elements have been proved on the balance of probabilities is a question for the jury. The defence reflects the view that the abnormality of mind experienced by the accused had such an effect on the accused’s capacity as to reduce his moral culpability and thereby diminish his legal liability.⁶⁶

The expression ‘abnormality of mind’ has been defined as ‘a state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal’.⁶⁷ It is not a requirement that the abnormality of mind is caused by a mental illness, though a mental illness will suffice for the operation of the defence.⁶⁸ Conditions such as anxiety and depression⁶⁹ and neurotic personality⁷⁰ will suffice for the purposes of the defence. The three prescribed causes which must be operative and result in an abnormality of mind are an arrested or retarded development of the mind, inherent causes or where the result is induced by disease or injury. Courts will distinguish between those causes which are due to external factors and prescribed causes thereby ensuring that an abnormality of mind due to transient drug use, hate or jealousy are excluded from the ambit of the defence.⁷¹ Due to problems experienced in practice with the defence as originally outlined certain statutory revisions to the United Kingdom formulation were recommended and subsequently implemented in the New South Wales Crimes Act.⁷² Amongst such changes was the introduction of the expression ‘underlying condition’ in place of the description found in the United Kingdom Act of the conditions which may give rise to an abnormality of mind.⁷³

The final element of the defence is the requirement that the abnormality of mind must have ‘substantially impaired [the accused’s] mental responsibility’. Both the defence of insanity and diminished responsibility arise as a result of an accused’s mental abnormality. However, an important difference between the two defences is in respect of the degree of impairment required before an accused’s responsibility for the offence will be affected. While insanity requires a total loss of capacity as a result of mental illness, diminished responsibility will only partially reduce the accused’s capacity leaving him or her partially responsible for his or her acts or omissions. As expressed in R v Byrne:⁷⁴

The expression ‘mental responsibility for acts’ points to a consideration of the extent to which the accused’s mind is answerable for his physical acts which must include a consideration of the extent of his ability to exercise willpower to control his physical acts…was the abnormality such as substantially impaired his mental responsibility for his acts in doing or being a party to the killing? This is a question of degree and essentially one for the jury.⁷⁵

The mental responsibility, which must be substantially impaired in order for the defence to be established, refers to both the accused’s ability to control his or her acts and to his or her degree of awareness of the nature and wrongness of the acts which he or she commits. The question for the jury in such a case is whether the accused had sufficient capacity to resist doing the act leading to the death and whether he or she had sufficient awareness of the nature and wrongness of this act.⁷⁶ Such a question will require a jury to undertake an evaluation of the degree of impairment in order to determine whether it may be called substantial and thereby warrant the reduction of the offence from murder to manslaughter. As expressed in R v Trotter:⁷⁷

Expert medical evidence is not really of great assistance in determining this crucial question of whether the impairment is substantial… [W]hether that impairment to the accused’s mental responsibility for his actions may ‘properly’ be called substantial (in the sense of being such as to warrant the reduction of the crime from murder to manslaughter) is not a matter within the expertise of the medical profession. This is a task for the tribunal of fact, which must approach the task in a broad commonsense way…It involves a value judgment by the jury representing the community (or by a judge where there is no jury), not a finding of medical fact.⁷⁸

I noted above that an excuse will be available to an accused who for some reason evinces a degree of impairment considered sufficient when assessed against an objective standard to reduce his or her blameworthiness. In the context of an excusatory defence such as diminished responsibility the use of a broad criterion invites a general normative assessment by the jury. In particular, in determining whether an accused’s requisite capacities are substantially impaired, a jury will be required to evaluate the accused’s culpability when judged against community standards. By means of such a value judgment the jury will decide whether the degree of impairment warrants a reduction of the accused’s culpability to be acknowledged by holding him or her liable for manslaughter rather than murder.

Mental impairment For an accused to raise the defence of insanity, or mental impairment as it is known in certain jurisdictions,⁷⁹ he or she must not only show that he or she is mentally ill, but also that, as a result of such mental illness, he or she has a mental malfunction which renders him or her not a fit subject of the criminal law. The defence is an exception to the operation of most excuses which rely for their operation on the accused meeting a normative standard before he or she may be excused. In contrast, where successfully pleaded, the defence of insanity establishes that the accused in failing to meet an objective standard is not a fit subject of the criminal law. The defence will be distinguished later in the chapter from the proposed defence of impaired consciousness.

As previously outlined, pursuant to the M’Naghten rules, the relevant mental malfunction will consist of either a lack of knowledge of the nature and quality of the act or a lack of knowledge that what he or she was doing was wrong.⁸⁰ As noted in Chapter 2, situations where an accused’s mind is so disturbed that he or she does not know the nature or quality of his or her act are rarely encountered in practice. In most instances where the defence is raised, the issue will turn on whether the accused knew he or she was doing wrong.⁸¹ Australian courts have interpreted ‘wrong’ to mean ‘morally’ rather than ‘legally’ wrong.⁸²