Defences I

The chapter discusses five major legal defences: age, insanity, automatism, intoxication, and mistake. These defences are critical in determining culpability and criminal liability.

Individuals under the age of ten cannot be deemed criminally liable according to law. The legal framework varies for children aged ten and above, who can be charged under criminal law regardless of their understanding of the law.

Insanity serves as a legal defence where the defendant (D) must demonstrate that, due to a disease of the mind, they lacked the understanding of the nature of their act or did not know it was wrong. This defence is further categorized into two types: insane and non-insane automatism. Insane automatism is connected to internal causes, while non-insane is linked to external factors.
Leading case: M’Naghten (1843)
- D, suffering from delusions, committed an act believing he was targeting the Prime Minister. The case established essential criteria to prove insanity:
  - Defect of reasoning from a disease of the mind.
  - Incapacity to know the nature of the act.
  - Incapacity to recognize that the act was wrong.
The burden of proof lies with D to establish these elements on the balance of probabilities.

Automatism refers to actions performed without conscious control, categorized as either non-insane (due to external factors) or insane (due to internal causes). The distinction influences the availability of defences.
Key cases:
- Quick (1973): D, a diabetic who consumed alcohol after insulin, could not be held under the defence of insanity since his condition stemmed from an external cause (insulin).
- Hennessey (1989): D, an insulin-dependent diabetic, suffered from hyperglycemia; the internal nature of his condition made the defence of insanity applicable here.

Intoxication cannot, in itself, function as a defence. However, it may indicate a lack of mens rea (the mental state of the defendant) in certain contexts.
Distinction is made between:
- Involuntary Intoxication: If D unknowingly ingests a substance, may serve as a defence if it negates mens rea.
- Voluntary Intoxication: Generally does not excuse criminal behaviour but may be considered in specific intent crimes. In cases of basic intent, voluntary intoxication typically indicates recklessness.
Landmark cases:
- Majewski (1977): Established that a person's voluntary intoxication does not negate liability for basic intent crimes.
- Kingston (1995): Emphasized that a drugged intent can still constitute mens rea.

The defence of mistake can negate mens rea in certain circumstances, particularly when D's mistake involves a factual element of the crime.
Important points:
- Most mistakes do not impact liability.
- Ignorance of the law is not a defence.
- If D makes a mistake regarding a factual element that negates mens rea, they may escape liability.
Example of mistakes in law:
- If identifying a person incorrectly (e.g., thinking a person is someone else) does not escape liability if the intention to harm is present.
Key cases illustrating mistake:
- Jaggard v Dickinson (1981): Here, D was judged based on her belief concerning lawful excuse, demonstrating how belief can influence legal standing.

Each defence possesses unique characteristics informing the outcome of legal accountability. Recognizing the nuances in these defences is crucial in criminal law, where the contexts and specific case details can decisively influence judicial outcomes.