Defences in Criminal Law

General defences and specific defences

General defences apply to a wide range of offences and offer complete exoneration, while specific defences apply to particular offences and may offer complete or partial defences.

The use of force must be necessary, the force used must be proportionate to the threat faced, and the defendant must have genuinely believed they were in imminent danger with no alternative means of escape.

Consent must be freely given and informed, and the defendant must have reasonably believed that the other party consented to the act in question.

There was an immediate threat of death or serious injury, the defendant reasonably believed the threat would be carried out if they did not commit the criminal act, and a reasonable person in the defendant's situation would have acted similarly.

They suffered from a mental disorder at the time of the offence, and the mental disorder caused them to be unable to appreciate the nature of the act or its wrongfulness.

A partial defence does not absolve the defendant of criminal responsibility entirely, but it may reduce the severity of the offence charged, while a full defence offers complete exoneration.

Diminished responsibility is a state of mind in which a person's mental capacity is diminished in such a way that they lack the ability to form the requisite intent for a crime, particularly in the case of murder. It is a partial defense that can lead to a conviction for a lesser offence, such as manslaughter.

The key elements for a successful diminished responsibility defense include: presence of an abnormality of mind, substantial impairment of mental responsibility, and a causal connection between the abnormality of mind and the killing.

In most jurisdictions, the burden of proof lies with the defendant to establish the presence of diminished responsibility on the balance of probabilities.

Medical evidence is crucial because it provides an assessment of the defendant's mental state and helps establish the presence of an abnormality of the mind, substantial impairment of mental responsibility, and a causal connection between the abnormality and the killing.

R v Byrne (1960)

Presence of an abnormality of mind, substantial impairment of mental responsibility, causal connection, and admissions and evidence.

Expert assessments involve examination and testimony from medical and psychiatric professionals to support the defence's assertions about the defendant's mental state.

Selection of experts, evaluation and analysis, and expert testimony.

A mental abnormality that affects the defendant's ability to think rationally, control their impulses, or understand the nature of their actions.

A clear link between the abnormality of mind and the act committed, showing that the mental impairment caused or contributed to the commission of the offence.

Insanity renders the defendant unable to understand their actions' nature or consequences or to identify their actions as wrong, whereas diminished responsibility significantly reduces their ability to form the necessary intent for a crime but does not completely prevent understanding the implications of their actions.

Involuntary psychiatric treatment and confinement to a mental health facility.

A conviction for manslaughter, a reduced offence compared to murder, and a possible reduced penalty.

Insanity, due to M'Naghten's delusion that rendered him unable to understand the nature and quality of his action.

A finding that Byrne's abnormality of mind substantially impaired his mental responsibility for the crime.

The insanity defence is a legal defence where a person charged with a crime is found not guilty because they lacked the mental capacity to understand that their actions were wrong.

M'Naghten Rule, Irresistible Impulse Test, Durham Rule, and Model Penal Code Test.

The primary purpose is to ensure that those who are genuinely unable to understand the consequences of their actions due to a mental disorder are not unfairly punished.

The presence of a diagnosed mental disorder, the relationship between the mental disorder and the criminal conduct, evidence of the defendant's inability to understand their actions or differentiate between right and wrong, and whether the defendant could control their conduct due to their mental disorder.

The case of Daniel M'Naghten, who attempted to assassinate the British Prime Minister and was found not guilty by reason of insanity.

The M'Naghten Rule considers a defendant legally insane if they were unable to understand the nature and quality of their actions, or could not differentiate between right and wrong due to a disease of the mind.

The Durham Rule states that a defendant is not criminally responsible if their criminal act was the product of a mental disease or mental defect.

The Model Penal Code test states that a defendant is not responsible for their actions if, as a result of a mental disease or defect, they lack substantial capacity to appreciate the wrongfulness of their conduct or conform their conduct to the requirements of the law.

The M'Naghten Rule has been criticized for being too narrow and based on outdated knowledge of mental health.

The Durham Rule has been criticized for being too broad, leading to its limited usage in few jurisdictions.

Ethical concerns, perceptions of moral responsibility, potential for loopholes and misuse, and the need for preventive measures against exploitation.

Limited understanding of mental disorders, misconceptions and stigmatization, disagreements on legal tests, and concerns about public safety.

Criteria for moral responsibility, moral vs. legal responsibility, justice vs. compassion, and responsibility of mental health professionals.

Faking insanity, manipulating expert witnesses, unwarranted application, and insufficient resources.

Offenders studying mental illness and coaching themselves, rigorous mental health evaluations; defence recruiting biased expert witnesses, strict standards for expert witnesses; unequal access to resources, allocating adequate resources to prosecution and court.

Automatism defence is a legal argument that a defendant acted unconsciously or involuntarily during the commission of an offence, leading to acquittal if successfully pleaded.

Insane automatism is caused by a mental illness or disorder (leads to not guilty by reason of insanity), while non-insane automatism is rooted in a medical condition or external factor (leads to full acquittal).

Provide evidence of the automatism, identify the type of automatism, establish the burden of proof, evaluate evidence and testimonies, and determine the verdict based on the acceptance of the automatism defence.

In the case of insane automatism, the accused may be found not guilty by reason of insanity; for non-insane automatism, the defendant can be fully acquitted.

The difference is in legal consequences: non-insane automatism leads to full acquittal, while insane automatism results in a verdict of not guilty by reason of insanity and potential indefinite treatment under medical supervision.

Challenges include proving the existence of automatism, distinguishing between insane and non-insane automatism, meeting the burden of proof, and overcoming judicial scepticism.

The jury accepted the defence of non-insane automatism and acquitted Parks of all charges, as he was found to have no control over his actions during the sleepwalking episode.

The key evidence included Parks' history of sleepwalking episodes, his lack of motive or animosity towards the victims, and testimonies of sleep specialists regarding his sleep disorder.

Difficulty in establishing evidence, potential misuse by defendants, and consequences following acquittal.

The debate focuses on whether defendants should be able to escape liability for criminal actions triggered by their own voluntary intoxication.

Strengthening evidentiary standards, clarifying legal definitions and distinctions, enhancing judicial education and training, and monitoring and evaluating outcomes.

To establish appropriate legal consequences and reduce subjectivity in the interpretation of the defence in criminal proceedings.

The primary focus of automatism defence in civil cases revolves around the defendant's inability to prevent unintentional harm suffered by the claimant due to unconscious and involuntary actions.