Mental Capacity Defences (OCR A-Level Law): Revision Notes

Insanity

Understanding the insanity defence

The insanity defence is a common law defence that allows a defendant to avoid criminal liability if they were suffering from a mental condition at the time of committing an offence. Despite being called "insanity", the legal definition does not align with modern medical understanding of mental illness. The defence is rarely used today due to the social stigma attached to the label, advances in mental health understanding, and the availability of alternative defences such as diminished responsibility for murder cases.

The legal framework for insanity combines statutory provisions with common law principles developed through case law. Understanding this defence requires careful analysis of both the procedural rules and the substantive test that must be satisfied.

Statutory definition

Section 2 of the Trial of Lunatics Act 1883 provides the statutory foundation for the defence. This section states that if at the time of committing an offence the defendant was insane, then the jury shall return a special verdict of not guilty by reason of insanity.

The common law test for establishing insanity comes from R v M'Naghten (1843), where the defendant killed a government official while suffering from extreme paranoia. Following this case, judges formulated what became known as the M'Naghten Rules. This test has remained the legal standard for insanity for over 180 years, despite significant changes in how society understands mental health conditions.

The M'Naghten Rules

The M'Naghten Rules set out a four-part test that the defendant must satisfy to successfully plead insanity. The complete definition states:

All elements of this test must be satisfied for the defence to succeed. Each component has been interpreted and clarified through subsequent case law.

Element 1: Labouring under a defect of reason

This first element focuses on the defendant's mental state and forms part of the mens rea requirement. The defendant must have been deprived of the power to reason, not simply failing to use their reasoning abilities. This is a crucial distinction that prevents the defence being used where someone acts carelessly or thoughtlessly.

The defect of reason must be substantial enough that the defendant lacks the capacity to exercise rational judgment about their actions. Temporary lapses in concentration or moments of confusion fall outside the scope of this defence.

Element 2: Arising from a disease of the mind

This second element forms part of the actus reus of the defence. The defect of reason must stem from a disease of the mind, which is a legal term rather than a medical concept. This distinction is important because the law defines what constitutes a disease of the mind according to legal policy considerations, not purely medical diagnosis.

The definition is deliberately broad and covers a wide range of conditions. It encompasses both organic diseases (those with a physical cause in the brain or body) and functional disorders (those without an identifiable physical cause). The condition can be permanent, transient, or intermittent. What matters legally is whether it affects the defendant's mental functioning.

A critical requirement established through case law is that the disease must be caused by an internal factor existing at the time of the criminal act. This internal/external factor distinction has become central to differentiating insanity from automatism.

The internal factor requirement is demonstrated through contrasting cases involving diabetes:

These cases show how the internal/external factor theory operates. If the cause comes from within the defendant's body or mind (like diabetes, epilepsy, or sleepwalking), it is internal. If it comes from outside (like insulin, a blow to the head, or drugs), it is external.

However, R v Coley (2013) shows limits to the internal factor approach. The defendant, a heavy cannabis user and computer gamer, stabbed a neighbour to death during what was described as a brief psychotic episode. The Court of Appeal held that because the psychosis was induced by the external factor of cannabis use, this was not insanity but voluntary intoxication (which is not a defence to murder).

Element 3: Did not know the nature and quality of the act

This third element, which forms part of the actus reus, requires that the defendant did not understand the physical nature and consequences of their actions. The phrase "nature and quality" refers to the physical character of the act, not its moral quality.

This element is satisfied when the defendant is so delusional or their consciousness so impaired that they do not comprehend what they are physically doing. This might occur when someone is in a state of unconsciousness or impaired consciousness, or lacks understanding or awareness due to a mental condition while conscious.

Element 4: Or, if he did know it, that he did not know what he was doing was wrong

This fourth element provides an alternative route to satisfying the test. Even if the defendant did understand the physical nature and quality of their actions, they can still rely on insanity if they did not know their actions were wrong.

R v Johnson (2007) confirmed this interpretation. The distinction between legal and moral wrongfulness remains important in determining whether this element of the test is satisfied.

Procedural rules for raising insanity

Several important procedural rules govern how the insanity defence operates in practice:

• Presumption of sanity: Every defendant is presumed to be sane. This means the starting point is that the defendant was mentally responsible for their actions.

• Who can raise the issue: The prosecution, defence, or judge can raise the issue of insanity during proceedings. This differs from most defences which only the defendant can raise.

• Burden of proof: The burden of proof rests on the defendant to establish insanity. This is unusual in criminal law, where the prosecution normally bears the burden of proof.

• Standard of proof: The defendant must prove insanity on the balance of probabilities (more likely than not), not beyond reasonable doubt. This is a lower standard than the criminal standard but reflects the fact that the defendant bears the burden.

• Fitness to plead: The judge decides whether the defendant is fit to plead (able to understand the proceedings and participate in their defence). This is a separate issue from whether the defendant was insane at the time of the offence.

• Medical evidence required: While the defendant bears the burden of proof, medical evidence must support the claim of disease of the mind, even though the final decision on whether it constitutes a legal disease of the mind is for the judge.

Consequences of a successful insanity verdict

When a defendant successfully establishes insanity, the jury returns a special verdict of "not guilty by reason of insanity". This amounts to an acquittal, meaning the defendant is not convicted of the offence. However, unlike a standard acquittal, this verdict triggers special sentencing provisions.

For murder, the sentence is mandatory indefinite hospitalisation under section 24(1)(3) of the Domestic Violence, Crime and Victims Act 2004. The defendant will be detained in a secure hospital until deemed safe for release.

For all other offences, section 5 of the Criminal Procedure (Insanity) Act 1964 (as amended by the Domestic Violence, Crime and Victims Act 2004) provides three disposal options available to the court:

1. Hospital order: The defendant is detained in a psychiatric hospital for treatment
2. Supervision order: The defendant is placed under supervision in the community with conditions
3. Absolute discharge: The defendant is released without conditions

The court selects the most appropriate option based on the circumstances of the case and the defendant's condition. This flexibility allows the court to tailor the outcome to the defendant's needs and public safety concerns.

Availability of the defence

Loake v DPP (2017) confirmed that insanity is available as a defence for any offence where the defendant possesses the mens rea for that offence and satisfies the M'Naghten Rules. In this case, the defendant had sent a large number of texts to her ex-husband. The court held that the defence is not restricted to serious offences but can apply to any crime where the elements are met.

Critical evaluation of the insanity defence

Several issues with the current law on insanity merit consideration:

Outdated definition: The M'Naghten Rules date from 1843 and do not reflect modern understanding of mental illness. Psychiatric medicine has advanced significantly, but the legal test has remained static.

Social stigma: Being labelled "insane" carries significant social stigma. This discourages defendants from raising the defence even when it might succeed, as they fear the lasting impact of the label on their reputation and future life.

Broad scope: Conditions like diabetes and sleepwalking can fall within insanity, even though these do not align with common understanding of mental illness. This extends the defence beyond what many would consider genuinely "insane" conditions.

Consequences deter use: The disposal options, particularly indefinite hospitalization for murder, may deter defendants from pleading insanity. They might prefer to take their chances at trial rather than face potentially long-term detention in a secure hospital.

Legal vs moral wrongfulness: The requirement that the defendant must not know their actions were legally wrong (rather than morally wrong) creates a high threshold. Many mentally ill people retain awareness that their actions breach the law even if their judgment is impaired in other ways.

Alternative defences available: For murder, diminished responsibility provides a partial defence that reduces the conviction to manslaughter without the stigma of the insanity label. This has made insanity even rarer in murder cases.

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