Criminal Law Defences and Causation

Comprehensive practice flashcards defining essential criminal law vocabulary, doctrines, statutes, and leading legal authorities across Self-Defence, Duress, Insanity, Automatism, Intoxication, Mistake, and Causation.

Self-Defence (Common Law Spheres)

A common law defence permitting a person to use reasonable force to defend themselves from attack, prevent an attack on another person, or defend their property.

Section 3(1) Criminal Law Act 1967

A statutory provision stating that a person may use such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders or persons unlawfully at large.

Reasonable Force (Palmer v R [1971])

The principle established by Lord Morris that a person under attack cannot be expected to weigh to a nicety the exact measure of defensive action, and acting honestly and instinctively in the heat of the moment provides strong evidence that reasonable action was taken.

R v Owino [1995]

The case affirming that the test for self-defence is objective based on subjective perception: a person may use such force as is objectively reasonable in the circumstances as they subjectively believe them to be.

Duty to Retreat (R v Bird [1985])

The legal principle confirming there is no rule requiring a defendant to run away or demonstrate an unwillingness to fight before using reasonable defensive force.

Pre-emptive Strike (Beckford v R [1988])

The principle stated by Lord Griffiths that a person about to be attacked does not have to wait for an assailant to strike the first blow or fire the first shot; circumstances may justify striking first.

Attorney-General's Reference (No 2 of 1983)

A ruling that making petrol bombs for protection during riots could constitute reasonable force in self-defence against an apprehended attack, establishing a 'lawful object' under s4(1) of the Explosive Substances Act 1883.

Mistake as to Self-Defence (R v Williams (Gladstone) [1984])

The rule that if a defendant labours under an honest mistake of fact regarding the need for self-defence, they must be judged according to that mistaken view, whether the mistake was reasonable or unreasonable.

Drunken Mistake in Self-Defence (R v O'Grady [1987])

The rule that a mistake of fact arising from voluntary intoxication cannot be relied upon to establish self-defence for any crime, whether of specific or basic intent.

Duress (Attorney-General v Whelan [1934])

A defence operating as an excusal where threats of immediate death or serious personal violence are so great as to overbear the ordinary powers of human resistance.

The Graham Test (R v Graham [1982])

A two-part test for duress requiring: (1) a subjective belief that circumstances placed life in immediate danger, compelling action; and (2) an objective assessment whether a sober person of reasonable firmness sharing the defendant's characteristics would have responded similarly.

Characteristics of the Reasonable Person (R v Bowen [1996])

The ruling establishing that a low IQ, short of mental impairment or defectiveness, is not a relevant characteristic under the objective limb of the Graham test, as it does not make a person less courageous or less able to withstand threats.

Safe Avenue of Escape (R v Lynch [1975])

The requirement in duress that the defence fails if the accused could reasonably have extricated themselves, sought police protection, or taken an available escape route.

Immediacy in Duress (R v Hudson and Taylor [1971])

The decision establishing that threats need not be carried out instantly within a courtroom to be imminent, provided they operate upon the defendant's will at the time the false evidence or offence occurs.

Voluntary Gang Membership (R v Sharp [1987])

The rule that the defence of duress is unavailable to a person who voluntarily joins a violent criminal gang or association which they know might coerce them into committing crimes.

Limitations on Duress (R v Howe [1987] & R v Gotts [1992])

The rule of law establishing that duress is never available as a defence to murder (R v Howe) or attempted murder (R v Gotts).

Duress of Circumstances (R v Willer [1986])

A defence arising where an accused is driven by the force of surrounding circumstances into committing an offence to avoid death or serious injury, initially recognised in road traffic offences.

External Circumstances Requirement (R v Rodger & Rose [1998])

The requirement that for duress of circumstances to apply, the compelling threat or danger must originate from sources external to the defendant, excluding internal pressures like clinical depression or suicidal impulses.

M'Naghten Rules (1843)

The legal test for insanity requiring proof on a balance of probabilities that the accused laboured under a defect of reason, caused by a disease of the mind, such that they did not know the nature and quality of the act, or did not know what they were doing was wrong.

Disease of the Mind (Legal Definition)

A legal rather than medical concept, encompassing any internal disorder or disease affecting the functioning of the mind, regardless of whether it manifests permanently or is prone to recur.

Defect of Reason (R v Clarke [1972])

A complete deprivation of the reasoning powers caused by a disease of the mind, which explicitly excludes mere absentmindedness or failure to use reasoning powers.

Wrongness under M'Naghten (R v Windle [1952])

The interpretation of 'wrong' under the M'Naghten rules strictly as legally wrong (contrary to law), rather than morally wrong.

Special Verdict

A verdict returned under the Trial of Lunatics Act 1883 and Criminal Procedure (Insanity) Act 1964 of 'not guilty by reason of insanity', which operates as an acquittal.

Insane Automatism

An impairment or disturbance of mental functioning caused by an internal factor (disease of the mind), properly giving rise to the defence of insanity.

Non-Insane Automatism (Bratty v AG for Northern Ireland [1963])

An involuntary act performed by muscles acting wholly without the control of the mind (such as a spasm, reflex, or convulsion) caused by an external factor, leading to a complete acquittal.

Total Loss of Control Requirement

The principle affirmed in Broome v Perkins and AG's Ref (No 2 of 1992) that automatism requires complete destruction of voluntary control; partial or reduced control is insufficient.

Internal vs External Factor: Diabetes

Hyperglycaemia resulting from untreated diabetes is an internal factor amounting to insanity (R v Hennessy), whereas hypoglycaemia caused by external insulin intake combined with lack of food is an external factor amounting to automatism (R v Quick).

Self-Induced Automatism (R v Bailey [1983])

The rule that self-induced automatism (not caused by alcohol or dangerous drugs) provides a defence to basic intent crimes only if the defendant was not reckless regarding the risks of their actions or inactions.

DPP v Majewski [1977]

The House of Lords ruling establishing that voluntary intoxication cannot negative mens rea in crimes of basic intent, because becoming voluntarily intoxicated is itself a reckless course of conduct.

Dutch Courage Rule

The legal principle that forming the intention to commit a crime and drinking alcohol to gain the courage to execute it deprives the defendant of any defence of intoxication.

Dangerous vs Non-Dangerous Drugs (R v Hardie [1985])

A distinction whereby taking a sedative or non-dangerous drug (such as Valium) that has an unexpected effect is treated under non-insane automatism rather than voluntary intoxication, unless the taking itself was reckless.

Mistake of Law

The established criminal doctrine that ignorance or mistake of the law excuses no one ('ignorantia juris non excusat'), exemplified in Arrowsmith (1974).

Mistake of Fact (B (a minor) v DPP [2000])

A defence based on an honest subjective belief in facts which, if true, would mean no mens rea was formed or no offence was committed; the belief does not need to be reasonable.

Factual Causation ('But For' Test)

The initial causation inquiry asking whether the prohibited harm would have occurred but for the actions of the defendant, established in R v White [1910].

Legal Causation (Culpable Act)

The requirement demonstrated in R v Dalloway (1847) that the resulting prohibited harm must be directly caused by the defendant's culpable or wrongful act, not merely an innocent act.

Substantial Cause Rule (R v Benge [1865])

The legal rule that the defendant's conduct need not be the sole cause of the resulting harm, provided it constitutes a more than minimal and substantial contributing cause.

Novus Actus Interveniens: Third Party (R v Pagett [1983])

An intervening act by a third party that breaks the chain of causation unless the intervention was a foreseeable and natural consequence of the defendant's original wrongdoing.

Novus Actus Interveniens: Victim's Act (R v Roberts [1971])

The principle that a victim's reaction only breaks the chain of causation if it is so daft or unexpected that no reasonable person could have foreseen it.

Medical Intervention in Causation (R v Cheshire [1991])

The principle that medical negligence will only break the chain of causation if it is so independent of the defendant's act and so potent in causing death that the defendant's acts are rendered insignificant.

Thin Skull Rule (R v Blaue [1975])

The rule requiring a defendant to take their victim as they find them, meaning pre-existing physical vulnerabilities or religious refusals of treatment (such as blood transfusions) do not break the chain of causation.