Moral responsibility and mental disorder: A philosophical exploration of the insanity defence

Introduction

People are usually assumed to have moral responsibility unless there is reason to think otherwise. Our commitment to blame and punishment (as ‘reactive attitudes’) ¹ either within criminal justice systems or our own personal relationships is very strong. One reason to doubt a person's moral responsibility however, is the presence of mental disorder, although when and how mental disorder affects moral responsibility is unclear. ² Philosophers are often more inclined than lawyers or psychiatrists to assume that mental disorder exculpates. Rather than propose necessary and sufficient conditions for moral responsibility, it is easier to identify cases which intuitively lack moral responsibility and attempt to justify or explain why they ought not to be blamed or punished.

Numerous jurisdictions include the legal defence of insanity which exculpates a defendant and effectively extinguishes their moral responsibility for a crime, usually because of mental disorder. Whether the legal test(s) are sufficiently clear, applied consistently and/or fairly remains a matter of debate. Psychiatrists are not experts in moral or legal responsibility despite them being called to given opinion evidence in court. Nevertheless even if the legal tests reflect our intuitions about moral responsibility, a philosophically coherent account about what justifies their existence is lacking.

In this article, I will examine the philosophical basis of the insanity defence as it currently operates in England and Wales and in other jurisdictions. I will argue that moral (and criminal) responsibility can be completely extinguished (not merely reduced) by certain mental disorders on the basis of any or all of the following (some of which already form part of the insanity defence in some jurisdictions):

Defects of reason – a reasons responsive account of moral responsibility (where a person is only weakly responsive or non-responsive to reasons to do otherwise).

Some of these elements overlap such as defects of reason (as supported by reasons-responsive accounts) and a lack of control, since defects of reason may impair a person's ability to exercise control. Nevertheless I argue that there should be a separate volitional element to the insanity defence in England and Wales as there is in other jurisdictions. We already have a strongly intuitive volitional element to the defence of automatism which exculpates a defendant on the basis of a total destruction of voluntary control ³ such as in epileptic seizures. I will argue that a loss of control short of automatism should apply to the insanity defence although it should be a very high threshold of near-total loss of control where mental disorder makes controlling one's conduct almost irresistible (similar to the total inability to control one's conduct in South Australia). ⁴

An inability to form mens rea in crimes of intention due to an inability for intentional actions (4) is not traditionally part of the insanity defence but should be considered alongside it because this too may rarely exculpate. This is rarely likely to succeed because as I have stated elsewhere ⁵ most people with mental disorders form intentions. It may only be in cases of severe thought disorder, delirium or severe depression that a person may lack capacity to form intentions due to an inability to form coherent enough beliefs and desires as a primary reason for acting. A drug-induced mental state (usually not grounds for an insanity defence) ⁶ leading to any of (1), (2), (3) or (4) can usually be considered culpable on the basis of ‘prior fault’ due to voluntary intoxication. ⁷

Although metaphysical debates about free will, moral responsibility and (in)compatibilism are beyond the scope of this article, I will briefly touch on them insofar as they are relevant to the need for a volitional element in the insanity defence. I will also consider manipulation arguments which are often used by incompatibalists to demonstrate the flaws in compatibilist accounts of moral responsibility. ⁸ These are relevant to the extent to which a person's reasons (1), knowledge (2), control (3) or intentions (4) (corresponding to my four proposed possible reasons for exculpation) are part of the manipulation of a mental disorder rather than part of their own actions. Intuitions about the nature of psychopathology varies considerably. ⁹ To the extent that a mental disorder is seen as a type of (external) manipulation it is likely to lead to exculpation, particularly in the case of delusions which are often the hallmark of insanity. ¹⁰ In this article, I will address conscious intentional actions involving prima facie morally blameworthy behaviour, rather than for example habitual actions, recklessness, omissions or praiseworthy behaviour.

Legal insanity in England and Wales

In England and Wales, insanity is defined in case law by the 1843 M’Naghten's Case. ¹¹ It is a common law defence to any criminal charge ¹² except for offences of strict liability. If successful, the defendant is given the special verdict of not guilty by reason of insanity. For a successful defence the defendant must have been labouring under a defect of reason caused by a disease of the mind. There is no requirement for a causal link between the defect of reason and the alleged offence. Whether a mental disorder is a disease of the mind is a question of law and it includes conditions such as paranoid schizophrenia, ¹³ but not intoxication alone. ¹⁴ As a result the defendant did not know the nature and quality of the act they were committing or they did not know that it was wrong. Although the legal test for insanity is of legal knowledge ¹⁵ the recent case of R v Keal ¹⁶ discussed below, is morally wrong according to the standards of ordinary people; if he knows that the act is morally wrong but not legally wrong, he cannot be said not to know that it is wrong.

Numbers of successful insanity defences in England and Wales, usually on the basis of the ‘wrongfulness’ limb, are surprisingly low. ¹⁷ As a result mental disorder is only ‘weakly relevant’ to insanity ¹⁸ perhaps because most psychotic people usually know the nature and quality of their act in a narrow sense. Unlike in other jurisdictions there is no volitional element, despite recommendations by the Law Commission. ¹⁹ The recent case of Keal demonstrates some of the conceptual problems with the defence in England and Wales.

R v Keal [2022] EWCA Crim 341

Jonathan Keal was convicted of three counts of attempted murder and sentenced to a hospital order under section 37/41 of the Mental Health Act. In September 2018 he attacked his father, mother and 91-year old grandmother with an array of weapons. He stabbed his father in the neck with a knife and hit him with a cricket bat whilst saying ‘I know I’m sorry I don’t want to, I’m sorry, I’m sorry dad’. Likewise whilst attacking his mother with scissors and puncturing her neck he said ‘I’m sorry this isn’t me it's the devil’. After his arrest he was admitted to a forensic psychiatric hospital. Psychiatric evidence confirmed the presence of psychosis, multiple delusions including a belief that he was possessed by the devil, that this impaired his capacity for rational thought and that he had a defect of reason. The prosecution opposed an insanity defence on the basis that he did know that what he was doing was wrong and against the law.

One of the psychiatrists noted that if Mr Keal believed that he was acting on the devil's instructions, then he must have known that what he was doing was wrong and that ‘the presence of delusions does not necessarily mean that free will has been removed’ as people might react in different ways to delusions. Another psychiatrist said that the delusions and hallucinations were compelling Mr Keal to act as he did although their intensity might wax and wane over time. Mr Keal's defence counsel argued that a compulsion to act (due to delusions, which deny a person agency) should be part of the insanity defence. They argued that the delusion extinguished his ‘choice’ and that it was therefore not ‘his’ act. The court concluded that moral knowledge in M’Naghten does not import any element of ‘choice’ or ‘agency’ and dismissed the idea of an uncontrollable impulse as part of the insanity defence. The court dismissed the appeal and suggested that the law should more properly be dealt with by Parliament.

It may seem intuitively unfair for a person whose delusions leave intact their knowledge of moral wrongfulness to be convicted, if they felt that they had no choice. This depends in part on the nature and strength of any delusional compulsion and the conceptual difficulties with the ability to do otherwise (did Mr Keal have a choice or was he compelled?) as explored below. This judgment reflects the strong intuition that some kind of control or choice is necessary for moral responsibility, alongside moral knowledge.

Legal insanity in other jurisdictions

As Mackay and Brookbands demonstrate, ²⁰ there is no universally agreed definition of insanity. English law has a narrower definition than many other jurisdictions, including the Chanel Island of Jersey which has departed from M’Naughten entirely; ‘suffering from mental disorder to such a substantial degree that he or she ought not to be held criminally responsible for doing so.’ ²¹ In Scotland insanity includes appreciating the nature or wrongfulness of the conduct, which is broader than the English test ²² although the insanity test is not met if it ‘consists only of a personality disorder which is characterised solely or principally by abnormally aggressive or seriously irresponsible conduct’. ²³ There is still no volitional element to the test in Scotland. In Northern Ireland ²⁴ however, insanity relates to a person's mental abnormality preventing him from appreciating what he is doing, appreciating that it is wrong or contrary to law, or from controlling his own conduct. This volitional element is also present in the Republic of Ireland test that they were ‘unable to refrain from committing the act’. ²⁵

Canada and New Zealand are closer to English Law in that there is no volitional element. The Canadian Criminal Code states that ‘No person is criminally responsible for an act committed or an omission made while suffering from a mental disorder that rendered the person incapable of appreciating the nature and quality of the act or omission or of knowing that it was wrong’. ²⁶ For insanity it appears that incapacity for knowledge rather than actual knowledge is the legal test. ²⁷ Despite the language of ‘appreciate’ for knowledge of the act, this has been interpreted in a narrow sense. In New Zealand the insanity defence is similarly still based on M’Naughten with language of ‘understanding the nature and quality of the act’ and ‘knowing that the act or omission was morally wrong, having regard to the commonly accepted standards of right and wrong’. ²⁸ This last part is slightly different to English law but there is still no volitional element.

In Australia however there is a mixture of different jurisdictions with differing insanity tests. The Commonwealth Criminal Code includes ‘did not know the nature and quality of the conduct’ and ‘did not know that the conduct was wrong’ but also includes ‘the person was unable to control their conduct’. ²⁹ New South Wales ³⁰ has no volitional element nor does Victoria but only knowledge of the nature and quality of the act and that the conduct was wrong. ³¹ In contrast in Queensland the test includes ‘capacity to control the person's actions’. ³² Tasmania includes a volitional element in ‘being deprived of any power to resist’. ³³ Western Australia includes ‘capacity to control his actions’ ³⁴ and South Australia includes ‘is totally unable to control the conduct’, ³⁵ arguably a higher threshold than other volitional tests.

The American Law Institute Model Penal Code (MPC) states that ‘a person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks substantial capacity either to appreciate the criminality (wrongfulness) of his conduct or to conform to the requirements of the law’. ³⁶ At the time of the publication of the MPC, the volitional element was present in nearly all US states. For example in State v White the New Mexico Supreme Court upheld a volitional element; ‘if, by reason of disease of the mind, defendant has been deprived of or lost the power of his will which would enable him to prevent himself from doing the act, then he cannot be found guilty’. ³⁷ Nevertheless after the attempted assassination of President Reagan by John Hinckley in 1982 who was acquitted on the basis of insanity, Congress passed the Insanity Defense Reform Act ³⁸ which reverted to a M’Naughten-style test without a volitional element. Some states have abolished the defence altogether.

In Norway, the mere presence of psychosis is sufficient for exculpation ³⁹ in contrast to other jurisdictions where although paradigmatic of insanity it is by no means sufficient. ⁴⁰ In the Netherlands there used to be five degrees of criminal responsibility ⁴¹ ; but in 2016 these were reduced to three; responsibility, diminished responsibility and (complete) insanity based on the guidelines for Forensic Evaluations in Criminal Cases in 2012. Nevertheless there is no legal definition of insanity and this inquisitorial system does not consider insanity to be a defence as such, although experts are asked to give their opinion about the degree of criminal responsibility. The United Nations guidance on Article 14 of the Convention on the Rights of Persons with Disabilities (CRPD) states that a declaration of ‘non-responsibility in criminal justice systems … is contrary to article 14 of the Convention since it deprives the person of his or her right to due process’. ⁴² Some have argued that insanity should be abolished on this basis. ⁴³

Given the variety of legal frameworks, it is unsurprising that many have called for reform to insanity law. ⁴⁴ The Keal case would be treated differently in different jurisdictions. Nevertheless the elements of knowledge and to a lesser extent, control have been popular since Aristotle ⁴⁵ as a reason for reducing or extinguishing moral responsibility. The variety of legal insanity approaches demonstrate that it is not intuitively obvious what the test should be.

I will consider the philosophical justifications for the current insanity test in England and Wales in addition to the need to add a volitional element. Although debates about the nature and necessity of free will (usually the ability to do otherwise or to exercise control in the absence of coercion) for moral responsibility are beyond the scope of this article such debates have relevance to the extent that mental disorder might exculpate if it impairs choice or control. Determinism is the thesis that there is exactly one physically possible future ⁴⁶ given the fixed laws of the universe. Compatibalism^47,48 is the thesis that there are possible worlds in which determinism is true and moral responsibility exists. I will assume a pragmatic compatibilist account of moral responsibility which is at least consistent with some legal concepts of insanity and our intuitions about exculpation on grounds of mental disorder. I will now consider my four proposed grounds for exculpation beginning with defects of reason.

Reasons-responsive accounts – a ‘defect of reason’

The idea that mental disorder exculpates due to deficits in rationality is popular ⁴⁹ but exculpating due to irrationality in general is ambiguous, ⁵⁰ particularly since reason is affected in very different ways depending on the particular mental disorder such as in phobias, addictions, compulsions, paranoid delusions or hallucinations. Disorders such as epileptic seizures with no conscious reasons for (involuntary) action might exculpate on the basis of an automatism defence instead. Psychosis and delusions in particular appear to affect reasons in a much more fundamental way (perhaps as a form of manipulation discussed below) than phobias. Exculpation on the basis of any defect of reason (even those due to phobias) appears too low a threshold whilst too high a threshold might mean that (like Keal) even severe forms of psychosis are not sufficient.

Fisher and Ravizza ⁴⁸ have proposed a moderate reasons’ responsiveness account which aims to get this balance about right. There must be a strong receptivity to reasons but only a weak reactivity to reasons. Being receptive to reasons means that a person would recognise a reason to do otherwise. Being reactive to reasons means that they would act to do otherwise as a result of that reason. Being weakly receptive or reactive means that there may only be one such reason. Being strongly reasons receptive or reactive means that there may be many reasons to do otherwise.

Rather than focus on the ability to do otherwise (‘regulatory control’ which libertarians would argue might require an indeterminate universe), Fisher and Ravizza argue for ‘guidance control’ (acting freely in the actual sequences of events) in response to an agent's own reasons, rather than due to an external agency, such as delusions. They argue that delusions stop a person being responsive to reasons to do otherwise. They also argue that reasons should be grounded in reality (i.e. a non-delusional reason) and have a moral element to them.

It is very difficult however to know to what extent a delusional person is grounded in reality and to what extent they are responsive to reasons. Consider Keal. He was grounded in reality to some extent (he knew he was trying to kill his family) but not others (the devil was telling him to kill them). He appears to be very unreactive to reasons. He was receptive to reasons to stop killing his family namely that it was morally wrong (‘I’m sorry’; assuming this was genuine remorse) and he presumably valued them (there is no evidence that he was previously callous towards them), but he did not appear able to stop despite wanting to (he appears to be receptive but not reactive to reasons).

One possible reason (grounded in reality) for him to have done otherwise would be if he reflected on the intense pain and injury he was causing his family. It's unclear if he would have been sufficiently receptive and reactive to that reason to stop following the devil's orders but if he had done so, he would have been sufficiently responsive to reasons to do otherwise and therefore morally blameworthy. If on the other hand he would not have acted any differently (despite reflecting on the intense pain and injury he was causing his family) then he is not sufficiently reasons-responsive and therefore should be exculpated. Lesser forms of psychosis might still be considered sufficiently reasons-responsive for moral responsibility for example where a person seems to be able to weigh up non-delusional reasons for following delusional orders or not.

McKenna considers reasons-responsivity to come in degrees ⁵¹ which has an intuitive appeal when comparing different types of psychosis or other mental disorders. Nevertheless insanity exculpates, which requires complete extinguishing of moral responsibility. Being completely unresponsive to reasons to do otherwise (which Keal appears to have been) may be sufficient particularly if the reasons are not a person's own as is the case in delusions. Whilst reason-responsive accounts are not immune from criticism they do have intuitive appear in providing a philosophical basis for defects of reason as exculpating on the basis of mental disorder. Having argued that defects of reason may exculpate I will now consider the knowledge limb of the insanity defence.

Moral knowledge and moral responsibility – ‘not knowing that it is wrong’

It is uncontroversial that if you lack knowledge of the nature and quality of an act that you should be exculpated for example if your psychosis leads you to cut a person's neck believing it to be a loaf of bread. ⁵³ It is difficult to see how you could have formed the relevant mens rea in the first place. Nevertheless moral (and legal) ignorance is more controversial because it is unclear what moral knowledge consists of. The nature of moral knowledge ⁵⁴ is beyond the scope of this article but according to Fisher and Ravizza ⁴⁸ we develop moral knowledge (and responsivity to moral reasons) as children by being exposed to reactive attitudes in a kind of social game where we come to view our actions as our own. By the age of criminal responsibility it is assumed that we have moral knowledge sufficient for moral responsibility.

In most cases of mental disorder including schizophrenia moral knowledge remains intact. ¹⁸ Psychotic patients do not act due to moral insensitivity per se ⁵⁶ but rather due to their delusions or hallucinations. Harman ⁵⁷ considers insufficient moral concern ⁵⁸ (which is often reduced in depression or psychosis) to explain exculpation but a lack of concern may actually be an explanation of culpability if we are blameworthy for lacking moral concern in the first place.

Philosophers sometimes argue that moral ignorance in psychopathy should exculpate ⁵⁹ on the basis of an inability to possess moral knowledge given deficits in empathy and moral emotions. ⁶⁰ This relies on an affective rather than merely intellectual conception of moral responsibility. In practice however, courts rarely exculpate on the basis of psychopathy ⁶¹ perhaps because only a narrower intellectual concept of knowledge is required. Even those who are psychotic rarely lack this intellectual moral knowledge. Keal possessed both non-moral knowledge (that he was attempting to kill his family) and moral knowledge or appreciation (‘I’m sorry’) which explains the finding of the court that he should not be exculpated on that basis. If Keal had believed that his actions were both lawful and morally praiseworthy due to delusions about God commanding him to act to save the world, he may well have lacked moral (and legal) knowledge sufficient for exculpation. Having considered defects in reason or defects in moral knowledge as reasons for exculpation, I will now consider the need for an exculpating volitional element to the insanity defence.

Control, the ability to do otherwise and Frankfurt examples

The Principle of Alternative Possibilities (PAP) states that a person is morally responsible for what he has done only if he could have done otherwise, an intuition which is very strong. ⁶² As the court said in Keal the presence of delusions does not necessarily mean that free will (control?) has been removed, but perhaps in Keal's case it did. If PAP is true, insanity should be amended to include a volitional element of choice or control in line with other jurisdictions. Although metaphysical debates about free will and the nature of reality are beyond the scope of this article, I will briefly consider Frankfurt's thought experiments because they are relevant to the volitional element.

In his paper ‘Alternative Possibilities and Moral Responsibility’ ⁶³ Frankfurt challenged PAP with a thought experiment in which a person, Black wants Jones to perform an action. Black decides that he will intervene if Jones is going to decide something else, and if he does, Jones will end up doing what Black wants (either by threat, a potion, hypnosis or manipulation of his brain). Nevertheless Black never has to show his hand because for reasons of his own, Jones performs the action anyway and Black never has to intervene. Frankfurt argues that Jones has the same moral responsibility as if Black had never been ready to intervene because what matters is not the ability to do otherwise, but the causal factors behind his action. What matters is what actually happens not what could have happened. ⁶⁴

It is uncontroversial that had Black acted, Jones would have been manipulated or coerced and not morally responsible (support for manipulation as exculpating as considered below). But if Jones acts for his own reasons, then he did not do it merely because he could have done nothing else. Frankfurt argues that PAP should be replaced with ‘a person is not morally responsible for what he has done if he did it only because he could not have done otherwise’. In this sense, Frankfurt holds to the idea that manipulation by others negates or excuses moral responsibility but only if this is the only reason for acting. What is important for moral responsibility is that a person acts ‘on their own’ and (as per a reasons-responsive account) that they act ‘for their own reasons’.

The relevance of these debates for mental disorder and moral responsibility is that coercion by an external agent often exculpates (in this case Black) and mental disorder may be seen as a type of manipulation. In addition, there is a strong intuition about some kind of control condition (even if only in a compatibilist sense) for moral responsibility. Fisher and Ravizza argue that ‘guidance control’ (acting freely in the actual sequences of events) in response to an agent's own reasons (rather than an external agency) is all that is needed to satisfy the control condition, and that there is no need for an ability to do otherwise (‘regulatory control’). Keal would be exculpated on such grounds since he is not acting freely, but coerced by delusions (not necessarily delusions of control, see below), and does not appear to act for his own (non-delusional) reasons.

Psychiatric disorders such as alcohol addiction, Obsessive Compulsive Disorder, kleptomania and binge-eating are often invoked as a paradigm of lack of free will and an impairment of control relevant to moral responsibility. ⁶⁵ Although these are sometimes regarded as irresistible impulses ⁶⁶ it is more likely that they are extremely difficult (rather than impossible) to resist and therefore only partially exculpatory. ⁶⁷ It is impossible to say if an impulse was irresistible or simply not resisted. ⁶⁸ It may be that the volitional element is too unreliable and that the epistemic element should remain the basis for the insanity test as it may be easier to measure over time, such as in the case of persistent delusions. As the American Psychiatric Association Insanity Defence Work Group stated, ‘the line between an irresistible impulse and an impulse not resisted is probably no sharper than that between twilight and dusk’. ⁶⁹

Given the difficulty with knowing whether impulses can be resisted, the control element should be treated with caution. Whether Keal could have ignored the devil's orders and not have tried to kill his family is impossible to know. This is also linked to reasons-responsiveness because control depends on acting differently in response to reasons. Nevertheless given the strong intuitions about PAP, there does need to be some kind of control condition such that if impulses are nearly irresistible, they may exculpate, but the threshold should be very high (short of automatism) and be clearly demonstrable.

Delusions of control and degrees of control

Having considered defects of reason, defects of knowledge and impairments in volition, I will briefly discuss delusions themselves because although they are paradigmatic of insanity, not all delusions are the same. According to the American Psychiatric Association (2013) DSM-V, a delusions is ‘a false belief based on incorrect inference about external reality that is firmly held despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary’. ⁷⁰ There are many different types of delusion in terms of both content (erotomanic, jealousy, persecution, grandiose, paranoid, Capgras, Cotard, religious or ontological) and form (monothematic, polythematic, circumscribed, elaborated) but also to the extent that they are integrated within the individual's belief system, the extent to which they lead to action, and how firmly a person holds to their delusion. ⁷¹

Although many patients with delusions may describe some element of having lesser control over their actions, those with delusions of control feel that an external agent or malevolent force is controlling their thoughts, emotions or bodily movements. Delusions of control are rarely isolated phenomena but are almost always accompanied by, and sometimes indistinguishable from persecutory delusions. Patients with anomalous experiences develop the narrative that they are being controlled because they are abnormally aware of the sensory consequences of their actions. ⁷²

Nevertheless phenomenological studies ⁷³ suggest that this lack of control is partial and never total; some actions remain under the patient's perceived control. In Keal his remark ‘this isn’t me it's the devil’ suggests that he perceives external control by the devil although his sense of self remains. The relevance of delusions of control is that they are arguably the type of delusion most likely to be considered similar to an external agent and most likely to impair volition. Nevertheless there may still be a choice (rather than an irresistible compulsion) to act ⁷⁴ on a delusion or not ⁷⁵ in most cases.

For those like Keal with potential (persecutory) delusions of control there appears to be diminishing degrees of reasons-responsiveness:

Delusionally moderately reasons-responsive – persecutory delusions of control are present but you retain at least a partial sense of agency such that you can do otherwise (in a compatibilist sense) if sufficient (non-delusional) reasons are present (being both strongly receptive and weakly reactive to at least one reason).

Whether Keal was in (1) or (2), or even (3) is debatable. If reflecting on the intense pain and injury he was causing his family were a strong enough reason for Keal to refrain from violence then he would fulfil (1) above. If this was irrelevant to his reasoning then he would fulfil (3). If he could have done otherwise but found the desire to carry out the devil's orders to be almost irresistible he would fulfil (2). It may be impossible to know.

I argue that both (2) and (3) should exculpate. In other words if you are unable (rather than just unwilling) to refrain from your conduct either totally (3) or almost totally (2) due to a compulsion from persecutory delusions of control (particularly if part of you wants to refrain as in Keal) you should not be found to be morally responsible. The degree of reasons-responsivity is sufficiently minimal as to make holding a person morally responsible in such as case, unjust. The insanity defence in England and Wales should incorporate a volitional element but the threshold for this should still be very high and should be total or near-total inability. Most delusional people will fulfil (1) above and therefore should not be exculpated.

Having considered defects in reason, moral knowledge and control, I will now turn to the fourth reason for exculpation namely that a person lacks the ability to form the relevant mens rea (in crimes of intent) due to being unable to form intentional actions. Although we have already been considering types of intentional actions (which may lack sufficient reasons, knowledge or control), we will now consider cases where a person cannot even form such an intention in the first place.

Intentional action and the capacity to form the relevant intention

I have considered the role of intentional action as a philosophical model for the legal concept of intent elsewhere. ⁷⁶ Nevertheless it is relevant for our purposes because the first limb of the insanity defence may overlap with a lack of capacity to form an intent. There is a significant difference between unintentional automatic movements such as a patella reflex, and choosing to move your leg which involves a desire, volition or act of the will. ⁷⁷

According to Davidson ⁷⁸ actions are caused by certain mental states. Agents have intentional explanations and reasons for why they act. The primary reason causing the action is a belief and desire pair; I believe something and have a desire to bring something about. Explanation of human action requires justification; it asks the question ‘why’, even if people act emotionally or habitually and even if the reason is flawed, illogical or non-existent. This sort of justification may therefore be very ‘weak’ in the sense that the reasons may be bad reasons but they are reasons nonetheless.

If intentional action requires agents to have desires and beliefs which form primary justificatory reasons for acting, it should not be controversial that people who are psychotic will usually still be capable of carrying out intentional actions because they have beliefs and desires. Beliefs may be delusional and desires may arise due to wanting to obeying hallucinations, but such individuals still act for justificatory reasons; ‘because the demons will punish me if I don’t obey them’.

There are some medical conditions which involve no intentional action (epileptic seizures or sleep walking) but for most mental disorders, conscious voluntary control and the existence of beliefs, desires and reasons for acting are retained. In these cases, it is difficult to argue that such people are unable to carry out intentional actions. The philosophical concept of intentional action is not the same as the legal concept of intent but it provides a reasonable basis for the idea that most people with psychosis can form the mens rea component of criminal intent.

Keal appears to have intended to kill his family for (delusional) reasons. He believed that the devil was ordering him to do so and desired to some extent to follow the devil's orders (since he did so) even if these desires were not his in the normal sense but rather delusions compelling him to act. There may be some mental states such as severe thought disorder, delirium or severe depression where beliefs and desires cannot be formed coherently enough as the primary reason for acting. In those cases they may well lack capacity to form the relevant mens rea in cases of intent. Nevertheless most people with psychosis will not lack capacity to form intent and therefore exculpation on these grounds will be rare. Having considered defects in reasons, knowledge, control and the ability to form intentions, I will now consider the problem of manipulation, and the relevance of history.

Manipulation arguments, mental disorder and the relevance of history

As discussed above, intuitions about the extent to which mental disorders are types of manipulation are relevant to how a person's reasons, knowledge or control are conceptualised. To the extent that mental disorder is seen as a type of external agency (not part of the self), it is likely to strengthen intuitions about exculpation. Just as brain tumours and seizures are considered external to the self, psychosis (particularly delusions of control) may be considered a type of manipulation.

Philosophers have created ‘manipulation’ scenarios (in contrast to coercion or influence) ⁷⁹ to explore whether inducing certain desires in individuals affects their moral responsibility. Although metaphysical arguments against compatibilism (which are often the purpose of manipulation arguments) are beyond the scope of this article, manipulation arguments are relevant to the question of whether mental disorders should be considered a type of manipulation.

Pereboom ⁸⁰ argues that in a deterministic universe, manipulation by neuroscientists makes no moral difference compared to ordinary human development (which presumably can include mental disorder) because everything is ultimately caused by factors beyond our control. It follows that if determinism is true, mental disorder is irrelevant to moral responsibility. Pereboom & McKenna ⁸¹ discuss ‘soft-line’ replies, the strongest of which is that naturalistic causal determinism is generally not brought about by other agents. ⁸² In experimental studies, intentional control by another agent intuitively appears to diminish moral responsibility. ⁸³ Involuntary intoxication (such as one's drink being spiked) is an exemption from criminal responsibility because of manipulation by another agent. ⁸⁴ Experimentally this remains the case even if the causative agent is an infection ⁸⁵ which probably extends to psychosis (particularly if it has an abrupt onset) which can be present in infectious delirium. ⁸⁶ The similarity of psychosis to infections may explain why we often want them to exculpate.

In addition to manipulation by an external agent, the history of how an action came about is relevant to our intuitions about exculpation. Mele's manipulation examples of desires being implanted (Chuck's bad values put into Sally, leading to homicide) are used to argue that how our desires came about is morally relevant. ⁸⁷ Although it is true that ‘we are inevitably fashioned and sustained, after all, by circumstances over which we have no control’⁸⁸ we do have some control over what influences us including reforming our own characters. Although historical compatibilism has the challenge of infinite-regress⁸⁹ what may be needed for moral responsibility is that desires come about in the right way which might exclude delusions and manipulation by external agents, rather than that we have complete control over them coming about.

I have argued above that mental disorder, particularly severe psychosis, may exculpate if it leads to defects in reasons, knowledge, control and an inability to form intentions. What may be driving our intuitions about such cases is the degree to which they are similar to manipulation by an external agent or an infection and lead to desires, beliefs or actions which are in some way not their own. Given that there is a spectrum of severity and types of mental disorder, the threshold for exculpation will vary depending on the facts of each case. Whether we view a particular case as enough of a type of manipulation may depend to some extent on how impaired we consider their reasons, knowledge, control or ability to form intentions. This leads to a kind of circularity in how strongly we think they are being manipulated and how willing we are to exculpate them. Such circularity may be inevitable but can shed light in what is driving our intuitions about where exculpation on the grounds of insanity should succeed.

Conclusion

In this essay I have examined insanity law as it operates in England and Wales and other jurisdictions as an exculpating model for extinguishing moral responsibility on grounds of mental disorder. I have argued that there are four circumstances where mental disorder may exculpate; (1) defects of reason; (2) defects of knowledge; (3) impairment of volition; and (4) an inability to form mens rea (in cases of intention). Any or all of these elements would be sufficient for exculpation but the threshold should be high.

Most legal tests for insanity include an epistemic element and some, a control element. Few are diagnostically driven but psychosis (including delusions) remains the most common insanity diagnosis. The Keal case in England and Wales demonstrates the inconsistencies between jurisdictions, the need for a control element and the need for defects of reason to be independently exculpating (via a lack of reasons responsiveness rather than always involving moral knowledge). Although the control element is very difficult to prove, the civil standard of proof (balance of probabilities) may make this easier. Given the existence of the automatism defence and morally relevant intuitions about the ability to do otherwise, a control element should be added to the insanity defence in England and Wales as long as the threshold remains high. Any of these four limbs below can be considered through the lens of reasons-responsive accounts but for clarity they should be considered separately.

It follows that exculpation equivalent to that of insanity due to a mental disorder (‘disease of the mind’) can be for all or any of the following:

Defects of reason (usually delusions) where the presence of mental disorder leaves a person weakly responsive (or non-responsive) to reasons to do otherwise such that the delusions (or other mental disorder) are almost irresistible and it is nearly impossible to do otherwise on the basis of non-delusional reasons.

Rather than providing necessary and sufficient conditions for moral responsibility, I have provided an account of when moral responsibility might be extinguished due to mental disorder, although such an account is not exhaustive. Such exculpation is rare but I have sought to provide a robust philosophical basis for it which arguably has intuitive appeal. Using these four criteria it is likely that Keal would be exculpated on the basis of (1) and/or (3) if these were part of the insanity defence. Other people with delusions might be more reasons-responsive or have more control over their actions and might therefore fail the insanity defence. The threshold should remain high and the control element should be clearly demonstrable. Any of these four criteria should be sufficient for exculpation since they are all individually morally relevant. The extent to which mental disorder is a type of manipulation should also be considered as this may be relevant to the assessment of these four criteria. Amending the insanity defence in this way, including a volitional element would be more just, more in line with other jurisdictions, more philosophically coherent and allow a more consistent approach for those with mental disorders who are charged with criminal offences.