Defences (AQA A-Level Law): Revision Notes
Defences 1: Capacity Defences
The AQA A-Level Law specification examines three key common law mental capacity defences that may excuse criminal liability. These defences recognise that certain individuals may lack the mental capacity required to be held fully responsible for their actions. Understanding these defences is essential for assessing criminal liability, particularly in problem questions where defendants claim they lacked the mental state necessary to commit a crime.
The three capacity defences covered in this note are:
- Insanity (also known as insane automatism)
- Automatism (also known as non-insane automatism)
- Intoxication
Each defence operates differently and has distinct legal requirements, consequences, and supporting case law. Understanding the distinctions between these defences is crucial for problem questions, particularly the difference between insanity and automatism based on the internal/external factor test.
Insanity (insane automatism)
Introduction to the insanity defence
The defence of insanity has both statutory and common law foundations. Section 2 of the Trial of Lunatics Act 1883 provides that if a defendant was insane at the time of committing an offence, the jury must return a special verdict of "not guilty by reason of insanity". This is not a straightforward acquittal but a special verdict with specific consequences.
The common law definition of insanity originates from the M'Naghten rules, established in 1843 following the case of R v M'Naghten. In this case, M'Naghten killed a government official while suffering from extreme paranoia. The case attracted significant criticism, leading judges to formulate a clear test for the insanity defence.
Despite being a recognised defence, insanity is rarely raised in modern criminal cases. This reluctance stems from several factors: the social stigma associated with being labelled "insane", the antiquated nature of the legal definition, significant advances in mental health understanding and care, and the introduction of alternative defences such as diminished responsibility for murder cases.
The M'Naghten rules
The M'Naghten rules provide the legal test for insanity. A defendant must prove on the balance of probabilities that at the time of the offence:
"The defendant was labouring under such a defect of reason, arising from a disease of the mind, that he did not know the nature and quality of the act he was doing, or, if he did know it, that he did not know that what he was doing was wrong."
This definition contains four key elements, each of which must be satisfied for the defence to succeed:
1. Labouring under a defect of reason (mens rea element)
This requires the defendant to be deprived of the power to reason, not merely failing to use their reasoning abilities properly. The distinction is crucial: a temporary lapse in concentration, absentmindedness, or confusion does not constitute a defect of reason.
R v Clarke (1972)
Clarke took items from a shop and forgot to pay for them, arguing this was due to her diabetes affecting her mental state.
The court held that a defect of reason requires the defendant to be deprived of their powers of reasoning, not simply confused or absentminded. Clarke's actions resulted from a momentary lapse rather than a true defect of reason.
Outcome: The defence failed because absentmindedness ≠ defect of reason
2. Arising from a disease of the mind (actus reus element)
"Disease of the mind" is a legal term rather than a medical term, though it must be supported by medical evidence. The courts have interpreted this element broadly to include:
- Organic or functional conditions
- Permanent or transient conditions
- Intermittent conditions
The Internal/External Factor Test
Crucially, the disease must be caused by an internal factor existing within the defendant at the time of the offence. This internal/external distinction is fundamental to differentiating insanity from automatism.
R v Kemp (1957) established that the defence concerns the mind rather than the brain. Kemp had hardening of the arteries (arteriosclerosis) and attacked his wife with a hammer during a period when his condition affected his mental functioning. The court held that even though the cause was a physical disease of the body, it qualified as a disease of the mind because it affected his mental functioning and was an internal factor.
The Diabetes Cases: Understanding Internal vs External Factors
Two contrasting diabetes cases illustrate the internal/external factor distinction that separates insanity from automatism:
R v Quick (1973): Quick, a diabetic, attacked a patient after taking his insulin but failing to eat sufficient food. The court held this was an external factor (the insulin injection) and therefore not insanity but potentially automatism.
R v Hennessy (1989): Hennessy, also diabetic, failed to take insulin for three days and then took a car without consent. The court held this was an internal factor (the diabetes itself causing high blood sugar) and therefore insanity rather than automatism.
Key distinction: Insulin injection = external factor; diabetes itself = internal factor
R v Burgess (1991) established that sleepwalking is considered an internal factor. Burgess attacked his girlfriend after falling asleep. The court held that sleepwalking arises from an internal condition and therefore falls within the definition of insanity rather than automatism.
3. Did not know the nature and quality of the act (actus reus element)
This element refers to the physical nature and consequences of the act, not the moral quality. The defendant must be delusional about what they are physically doing. This may occur due to:
- A state of unconsciousness or impaired consciousness
- Lack of understanding or awareness resulting from a mental condition while conscious
Illustrative Scenario
If a defendant believed they were cutting a loaf of bread when they were actually stabbing a person, they would not know the nature and quality of their act. They understand the physical action (cutting) but are delusional about what they are actually doing.
4. Or, if he did know it, that he did not know what he was doing was wrong (mens rea element)
This alternative limb applies where the defendant understood what they were physically doing but did not understand it was wrong. Critically, "wrong" means legally wrong, not morally wrong.
R v Windle (1952)
Windle gave his wife a fatal overdose of aspirin. When arrested, he said "I suppose they will hang me for this".
This statement showed he knew his actions were legally wrong, even though he may have believed he was morally justified in ending his wife's suffering.
Outcome: The defence failed because knowledge of legal wrongness defeats the defence.
R v Johnson (2007) confirmed this approach, emphasising that the defence fails if the defendant understood their actions were legally wrong, regardless of any mental illness affecting their moral judgment at the time.
Procedural rules for raising insanity
The law has developed several important procedural rules:
Key Procedural Points
Presumption of sanity: Every defendant is presumed sane unless the contrary is proved. This presumption places the burden on those claiming insanity to establish it.
Who can raise insanity: The prosecution, defence, or judge can raise the issue of insanity. This differs from most defences, which only the defence can raise.
Burden of proof: The defendant bears the burden of proving insanity on the balance of probabilities (more likely than not). This is an exception to the usual criminal law rule that the prosecution must prove guilt beyond reasonable doubt.
Fitness to plead: The judge decides whether the defendant is fit to plead (able to understand the proceedings and instruct their legal representatives). This is a separate issue from whether the defendant was insane at the time of the offence.
Consequences of an insanity verdict
While insanity is a common law defence, the consequences of a successful defence are set out in statute. If the jury finds the defendant was insane at the time of the offence, they must return the special verdict of "not guilty by reason of insanity". This amounts to an acquittal but with significant consequences.
Sentencing Outcomes Depend on the Offence
For murder, the sentence is indefinite hospitalisation under section 24(1)(3) of the Domestic Violence, Crime and Victims Act 2004. The defendant will be detained in a secure psychiatric facility until the authorities are satisfied they no longer pose a risk.
For all other offences, section 5 of the Criminal Procedure (Insanity) Act 1964 (as amended by the 2004 Act) provides three disposal options:
- Hospital order: The defendant is detained in a psychiatric hospital for treatment
- Supervision order: The defendant is released into the community under supervision
- Absolute discharge: The defendant is released without conditions
The judge has discretion to choose the most appropriate disposal based on the circumstances and the risk posed by the defendant.
Reform proposals for insanity
The Law Commission published a discussion paper in 2013 titled "Criminal Liability: Insanity and Automatism", which highlighted several problems with the current law and proposed reforms:
Outdated and offensive terminology: Describing someone with a medical condition such as diabetes or epilepsy as "insane" seems arbitrary and outdated. The Law Commission noted that the term is "off-putting or even offensive" to modern society.
Mismatch with modern psychiatry: There is a significant disconnect between the legal definition of insanity and modern psychiatric understanding of mental health conditions. The M'Naghten rules were formulated in 1843 and do not reflect contemporary medical knowledge.
Inconsistent Decisions
The Law Commission described the contrasting decisions in R v Quick (1973) and R v Hennessy (1989) as "odd". Both involved diabetics, yet one was considered insane while the other was not, based solely on whether the problem arose from taking insulin (external) or not taking it (internal).
Overly broad scope: The internal/external factor requirement makes the potential scope of the defence "surprisingly wide", potentially catching defendants who would not ordinarily be considered mentally ill.
Sleepwalking inconsistencies: Cases involving sleepwalking have led to inconsistent outcomes, with some defendants receiving the special verdict while others are completely acquitted, depending on how the case is characterised.
Key cases on insanity
| Case | Facts | Legal principle |
|---|---|---|
| R v M'Naghten (1843) | M killed a government official while suffering from extreme paranoia | The case led to criticism of the law, prompting judges to formulate the test for insanity that bears M'Naghten's name |
| R v Clarke (1972) | C took items from a shop and forgot to pay, arguing her diabetes affected her mental state | A defect of reason requires being deprived of the power to reason, not simply being confused or absentminded |
| R v Kemp (1957) | K had hardening of the arteries and attacked his wife with a hammer | The defence concerns the mind, not the brain. Physical diseases affecting mental functioning can constitute a disease of the mind |
| R v Quick (1973) | Q, a diabetic, attacked a patient after taking insulin but not eating sufficient food | The disease of the mind must originate from an internal source. The insulin was an external factor, so this was not insanity |
| R v Hennessy (1989) | H, a diabetic, failed to take insulin for three days and took a car without consent | The disease must originate from an internal source. The diabetes itself was internal, so this was insanity |
| R v Burgess (1991) | B attacked his girlfriend after falling asleep | Sleepwalking is an internal factor and therefore constitutes insanity rather than automatism |
| R v Coley (2013) | D, a heavy cannabis user and 'gamer', stabbed a neighbour while having 'a brief psychotic episode' | The Court of Appeal held that due to the external factor (cannabis), this was voluntary intoxication, not insanity |
| Loake v DPP (2017) | L sent numerous texts to her ex-husband | Insanity is available as a defence for anyone who possesses the mens rea for an offence and satisfies the M'Naghten rules |
Automatism (non-insane automatism)
Introduction to automatism
Automatism is a complete defence available when a person's consciousness is so impaired that they are acting in a state of physical involuntariness. The fundamental principle is that if a person cannot control their physical actions, they cannot form the mens rea (guilty mind) required for criminal liability. Therefore, they should not be held responsible for their involuntary actions, however serious or unfortunate the consequences.
The essential characteristic of automatism is that the defendant's actions are not the product of conscious will or voluntary control. Their muscles act without direction from their conscious mind.
The definition of automatism
The leading definition of automatism comes from Lord Denning in Bratty v Attorney General for Northern Ireland (1963):
"An act which is done by the muscles without any control by the mind such as a spasm, a reflex action or a convulsion; or an act done by a person who is not conscious of what he is doing such as an act done whilst suffering from concussion or whilst sleepwalking."
In Bratty, the defendant strangled and killed his girlfriend during what he claimed was a "blackout". The case established the legal test that courts use to determine whether automatism applies.
Requirements for the automatism defence
To successfully plead automatism, the defendant must satisfy three key requirements:
1. There must be an external factor
This is the crucial distinguishing feature between automatism and insanity. The cause of the involuntary behaviour must come from outside the defendant's body or mind. If the cause is internal (arising from the defendant's own mental or physical condition), it will be classified as insanity rather than automatism.
Examples of External Factors
External factors that can give rise to automatism include:
- Being struck on the head by an object
- Slipping on ice
- Being overcome by a sudden illness
- Involuntary physical reactions such as hiccups or a coughing fit
- A temporary loss of control due to a radical external event
Kay v Butterworth (1945) provides an unusual example: being attacked by a swarm of bees while driving could constitute an external factor causing automatism if it resulted in total loss of control over the vehicle.
Hill v Baxter (1958) established that the defendant bears the evidential burden of proof for automatism. In this case, the defendant hit a car at a junction and claimed to remember nothing. The court held that once the defence raises sufficient evidence of automatism, the prosecution must then prove beyond reasonable doubt that the defendant was not acting involuntarily.
The Diabetes Cases Revisited
The diabetes cases again illustrate the internal/external distinction:
- R v Quick (1973): The external insulin injection caused the involuntary state, so automatism was potentially available
- R v Hennessy (1989): The internal diabetes caused the involuntary state, so only insanity was available
R v T (1990) established that external psychological trauma can constitute an external factor if sufficiently severe. T took part in a robbery three days after being raped. She argued she was in a dream-like state and suffered from post-traumatic stress disorder (PTSD). The court accepted that the external stress of the rape could give rise to automatism if it was severe enough to cause a total loss of control.
2. There must be a total loss of control
Complete Loss of Control Required
The loss of control must be complete and total. Any impaired, reduced, or partial control will invalidate the defence. This is a strict requirement that significantly limits the availability of automatism.
Worked Example: Attorney General's Reference No. 2 of 1992 (1993)
A truck driver drove in a trance-like state along the motorway's hard shoulder and hit and killed two people. Medical evidence suggested he was suffering from "driving without awareness" due to repetitive visual stimuli.
The Court of Appeal held that because the driver retained some control (he steered the vehicle and kept it on the hard shoulder), automatism was not available.
Key principle: The requirement is for total loss of control, not merely impaired or reduced control.
3. The automatism must not be self-induced
Automatism will not succeed as a defence if the defendant knows their conduct will bring about an automatic state. This principle is based on the defendant's fault in voluntarily placing themselves in a situation where they know they may lose control.
The most common example is intoxication. If a defendant becomes intoxicated through their own voluntary actions and then commits a crime while in an involuntary state due to the intoxication, they cannot rely on automatism. Instead, the rules on intoxication apply (discussed later in this note).
However, there is an important exception: where the defendant does not realise their self-induced actions would cause automatism and they were not reckless in their behaviour.
Worked Example: R v Hardy (1984)
Hardy took prescription medication not knowing it would cause him to lose control.
Because he did not know and was not reckless about the risk, his automatism was not considered self-induced and the defence was potentially available.
Key principle: Lack of knowledge + not reckless = defence potentially available
R v Bailey (1983): Three Rules on Self-Induced Automatism
The case established three rules regarding self-induced automatism:
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If the defendant knows their conduct will bring about an automatic state, automatism is not available for basic intent crimes
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If the defendant does not know but ought to have known (is reckless), automatism is not available for basic intent crimes
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If the defendant neither knows nor ought to have known (is not reckless), automatism may be available even for basic intent crimes
Consequences of successful automatism
If the defence of automatism is successful, it results in a complete acquittal. Unlike insanity, there is no special verdict and no disposal options such as hospital orders or supervision orders. The defendant is simply found not guilty and released.
R v C (2007) confirmed that a successful automatism defence leads to a complete acquittal without any conditions or ongoing obligations.
This significant difference in outcome explains why defendants strongly prefer to argue automatism rather than insanity, even though the underlying facts may be similar. The complete acquittal from automatism is far more favourable than the special verdict and potential detention or supervision that follows an insanity verdict.
Reform proposals for automatism
The Law Commission's 2013 discussion paper "Criminal Liability: Insanity and Automatism" proposed significant reforms to the defence of automatism:
Abolish the current common law defence: The existing common law defence would be replaced with a new statutory defence with clearer criteria.
New defence triggered only by total loss of capacity: The reformed defence would be available only where there is a total loss of capacity to control one's actions, maintaining the strict requirement for complete involuntariness.
Not caused by a recognised medical condition: The new defence would apply only when the loss of control is not caused by a recognised medical condition. This maintains the distinction from insanity but expresses it in more modern medical terminology.
Defendant not culpably responsible: The defence would be available only where the defendant was not culpably responsible for the loss of control. This codifies the existing principle regarding self-induced automatism.
New 'recognised medical condition defence': Defendants who raise automatism due to a recognised medical condition (such as diabetes or epilepsy) would be required to plead a new defence specifically for such conditions, rather than the traditional insanity defence with its outdated terminology.
Complete acquittal outcome: A successful outcome in raising the new defence would continue to lead to a complete acquittal, maintaining the current position.
Burden of proof: The defence would continue to have the evidential burden (raising sufficient evidence), while the legal burden would remain with the prosecution (proving beyond reasonable doubt that the defence does not apply).
Key cases on automatism
| Case | Facts | Legal principle |
|---|---|---|
| Bratty v A-G for Northern Ireland (1963) | D strangled and killed his girlfriend during a claimed "blackout" | Lord Denning created the legal test for automatism that courts still use today |
| Hill v Baxter (1958) | D hit a car at a junction and claimed to remember nothing | The defendant bears the evidential burden of proof for automatism. If evidence is raised, the prosecution must disprove it |
| R v Quick (1973) | Quick, a diabetic, attacked a patient after taking insulin but not eating sufficient food | External factors (the insulin injection) can give rise to automatism rather than insanity |
| R v Hennessy (1989) | Hennessy, a diabetic, failed to take insulin for three days and took a car without consent | Internal factors (the diabetes itself) give rise to insanity rather than automatism |
| R v T (1990) | T took part in a robbery three days after being raped, claiming PTSD caused a dream-like state | External stress can give rise to automatism if severe enough to cause total loss of control |
| A-G Reference No. 2 of 1992 (1993) | A truck driver drove in a trance-like state along the motorway's hard shoulder and killed two people | The requirement is for total loss of control. Impaired or reduced control is insufficient for automatism |
| McGhee (2013) | M drank himself into an involuntary state and was charged with assault offences | Self-induced automatism through voluntary intoxication cannot be used as a defence |
Intoxication
Introduction to intoxication
Intoxication occupies a unique and somewhat controversial position in criminal law. It is not truly a defence in the traditional sense, but rather a factor that may prevent the prosecution from proving the defendant formed the necessary mens rea for the offence. The law on intoxication represents a careful balance between two competing principles:
The Two Competing Principles
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The fundamental principle that we should not punish people who lack the mens rea for an offence
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The public policy need to protect society from people who commit crimes after voluntarily becoming intoxicated
This tension between legal principle and public policy has resulted in complex rules that distinguish between different types of intoxication and different categories of crime.
What is intoxication?
The term "intoxication" covers the effects of various substances including:
- Alcohol
- Illegal drugs
- Prescription or over-the-counter drugs
- Other substances such as solvents
Intoxication is relevant to criminal liability when it prevents the defendant from forming the mens rea required for the offence. The key question is whether the defendant was so intoxicated that they could not form the necessary intention, knowledge, or recklessness.
The two types of intoxication
The law distinguishes between two main categories of intoxication, which have very different legal consequences:
1. Voluntary intoxication
Voluntary intoxication occurs when the defendant chooses to take a substance, knowing it can cause intoxication. This includes situations where the defendant:
- Deliberately drinks alcohol
- Knowingly takes illegal drugs
- Takes prescription drugs knowing they may cause intoxication
Dangerous vs Non-Dangerous Drugs
The Court of Appeal in R v Bailey (1983) and R v Hardie (1985) further distinguished between "dangerous" drugs and "non-dangerous" drugs:
Dangerous drugs: These are drugs that are well known to cause unpredictability, aggression, or loss of control. Examples include alcohol, heroin, cocaine, and LSD. Knowingly taking dangerous drugs constitutes voluntary intoxication.
Non-dangerous drugs: These are drugs not generally known to cause unpredictability or aggression. Examples might include mild sedatives or common medications. Taking non-dangerous drugs may or may not count as voluntary intoxication, depending on whether the defendant understood the potential impact on them.
R v Hardie (1985)
Hardie took Valium (a sedative) during an emotional crisis. He later started a fire.
The court held that because Valium is generally a calming drug and Hardie did not know it might affect him in an unpredictable way, this was not voluntary intoxication.
Key principle: Taking non-dangerous drugs without knowledge of their effects ≠ voluntary intoxication
2. Involuntary intoxication
Involuntary intoxication occurs when the defendant was unaware they were taking an intoxicating substance. Common scenarios include:
- Having one's drink "spiked" with alcohol or drugs without knowledge
- Taking prescription drugs that have unexpected or unforeseen effects
- Being forced or tricked into consuming intoxicating substances
Critical Point: Mens Rea Still Required
The legal consequences of involuntary intoxication depend on whether the defendant formed the mens rea:
- If the defendant did not form the mens rea due to involuntary intoxication, they are not guilty
- If the defendant did form the mens rea despite being involuntarily intoxicated, they can still be guilty
R v Kingston (1994)
Kingston, a known paedophile, drank coffee that had been drugged by others attempting to blackmail him. While involuntarily intoxicated, he sexually abused a young boy.
The House of Lords held that despite the involuntary intoxication, Kingston knew what he was doing and formed the mens rea for the offence. He could not stop himself due to the intoxication, but he still intended his actions.
Outcome: Guilty despite involuntary intoxication, because he still formed the mens rea.
Voluntary intoxication and the specific/basic intent distinction
The rules on voluntary intoxication depend on whether the offence is classified as one of "specific intent" or "basic intent". This distinction is crucial:
Specific intent crimes require intention as the mens rea. The prosecution must prove the defendant intended the consequence or had a specific purpose in mind. For specific intent crimes:
- Voluntary intoxication can be a complete defence if the defendant was so intoxicated they could not form the required intention
- This is because intoxication may prevent the defendant from forming the specific intention required
Basic intent crimes can be committed recklessly or with a lower level of mens rea. For basic intent crimes:
- Voluntary intoxication is never a defence
- The rationale is that voluntarily becoming intoxicated is itself a reckless course of conduct
- This recklessness provides sufficient mens rea for crimes that can be committed recklessly
| Specific intent crimes | Basic intent crimes |
|---|---|
| Murder | Manslaughter |
| Wounding or causing GBH with intent (s.18 OAPA 1861) | Wounding or inflicting GBH (s.20 OAPA 1861) |
| Theft | Assault occasioning actual bodily harm (s.47 OAPA 1861) |
| Robbery | Common assault |
Important principles on intoxication
A drunken intent is still an intent
R v Sheehan and Moore (1975) established that if a defendant forms the necessary mens rea despite being intoxicated, they are still guilty. Being drunk does not excuse criminal behaviour if the defendant still intended to commit the crime.
Attorney General for Northern Ireland v Gallagher (1963)
Gallagher decided to kill his wife and bought whisky and a knife. He drank the whisky to give himself "Dutch courage" before killing her.
The House of Lords held that because he formed the intention to kill before becoming intoxicated, he was guilty of murder.
Key principle: Drinking to give oneself courage to commit a crime is no defence. The mens rea existed before the intoxication.
Voluntary intoxication never excuses basic intent crimes
The policy reason for denying the defence for basic intent crimes is that:
- Voluntarily becoming intoxicated is itself a reckless course of action
- This recklessness satisfies the mens rea for crimes that can be committed recklessly
- Therefore, the defendant had the necessary mens rea when they chose to become intoxicated
DPP v Majewski (1977)
Majewski consumed excessive amounts of alcohol and drugs before getting into a fight. He was charged with assault occasioning actual bodily harm (a basic intent crime).
The House of Lords upheld his conviction, holding that his recklessness in becoming intoxicated provided the necessary mens rea for the offence.
Key principle: Voluntary intoxication cannot be a defence to crimes of basic intent.
Complete incapacity requirement
DPP v Beard (1920) established that the defendant must be so intoxicated that they were incapable of forming the required intention. Mere impairment or reduced capacity is not sufficient. The threshold is very high.
Subjective recklessness and intoxication
R v Harris (2013) raised an interesting question about the relationship between voluntary intoxication and subjective recklessness. The Court of Appeal made an obiter (non-binding) comment suggesting that voluntary intoxication perhaps should not be a defence even to offences requiring subjective recklessness. The court noted:
"We see some force in the argument that voluntary intoxication ought not to be a defence to an offence involving recklessness, even subjective recklessness; it may fall for decision in a later case."
This comment hints at potential future development of the law, though it remains obiter and has not been followed in subsequent cases.
Recent cannabis case
R v Coley (2013) involved a heavy cannabis user and video game player who stabbed a neighbour to death while experiencing "a brief psychotic episode". The Court of Appeal held that because the psychotic state was caused by an external factor (the cannabis), this was a case of voluntary intoxication rather than insanity. There was no complete loss of control to establish automatism. Therefore, the ordinary rules on voluntary intoxication applied.
Reform proposals for intoxication
The Law Commission published a report "Intoxication and Criminal Liability" in 2009, recommending significant reforms:
Abolish the specific/basic intent distinction: The confusing terminology of specific and basic intent would be replaced with clearer language.
Retain the voluntary/involuntary distinction: The fundamental distinction between voluntary and involuntary intoxication would be preserved, as this reflects the policy considerations underlying the defence.
Primary presumption against intoxication: There would be a presumption that the defendant was not intoxicated. The defendant would need to raise evidence of intoxication to displace this presumption.
Secondary presumption of voluntary intoxication: If the defendant raises evidence of intoxication, there would be a presumption that it was voluntary intoxication.
Burden on defendant for involuntary intoxication: If the defendant claims the intoxication was involuntary (for example, their drink was spiked), they would have to prove this on the balance of probabilities.
These reforms aim to simplify the law while maintaining the policy balance between protecting defendants who genuinely lacked mens rea and protecting society from those who commit crimes after voluntarily becoming intoxicated.
Key cases on intoxication
| Case | Facts | Legal principle |
|---|---|---|
| DPP v Beard (1920) | Beard argued intoxication as a defence to murder | The defendant must be completely incapable of forming the mens rea for intoxication to provide a defence |
| Attorney General for NI v Gallagher (1963) | Gallagher decided to kill his wife, bought whisky and a knife, drank the whisky, then killed her | If mens rea is formed before intoxication, the defendant is guilty. "Dutch courage" is no defence – a drunken intent is still an intent |
| DPP v Majewski (1977) | Majewski consumed excessive alcohol and drugs before getting into a fight | Voluntary intoxication cannot be a defence to basic intent crimes. Becoming intoxicated is reckless conduct that satisfies the mens rea |
| R v Kingston (1994) | Kingston, a paedophile, drank drugged coffee and abused a young boy while involuntarily intoxicated | Despite involuntary intoxication, if the defendant still forms the mens rea, they are guilty. Kingston knew what he was doing even though he could not stop himself |
| R v Coley (2013) | Coley, a heavy cannabis user, stabbed a neighbour while having a psychotic episode | Because the psychotic state was caused by an external factor (cannabis), this was voluntary intoxication, not insanity or automatism |
Key Points to Remember:
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Insanity is defined by the M'Naghten rules (1843) requiring a defect of reason from a disease of the mind. The defendant must prove this on the balance of probabilities. A successful defence results in a special verdict of "not guilty by reason of insanity" with potential hospital detention or supervision.
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Automatism requires an external factor causing a total loss of control. It must not be self-induced. Unlike insanity, a successful automatism defence results in a complete acquittal with no special verdict or consequences.
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The crucial distinction between insanity and automatism is the internal/external factor test: internal factors (from within the defendant's body or mind) lead to insanity, while external factors lead to automatism.
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Intoxication is not a true defence but may prevent the prosecution proving mens rea. Voluntary intoxication can be a complete defence to specific intent crimes (like murder, s.18 GBH, theft) but is never a defence to basic intent crimes (like manslaughter, s.20 GBH, assault).
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Involuntary intoxication (being spiked) does not automatically provide a defence. If the defendant still formed the mens rea despite being involuntarily intoxicated, they remain guilty of the offence.
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All three capacity defences have been criticised and are subject to reform proposals from the Law Commission, particularly regarding outdated terminology, inconsistent application, and the mismatch between legal definitions and modern medical understanding.