Core principles of criminal liability - General defences

Learning Outcomes

After studying this article, you will be able to identify and explain the key general defences available in criminal law. You will understand the scope of each defence, when and how they apply, and their requirements. You will be able to define essential terms relevant for SQE2, distinguish between justification and excuse defences, and avoid common areas where exam candidates make mistakes on self-defence, intoxication, and automatism.

SQE2 Syllabus

For SQE2, you must be able to explain, apply, and distinguish core general defences to criminal liability. In your revision, focus on:

• the definition and operation of general defences including self-defence, intoxication, automatism, and insanity
• recognising the elements required to successfully rely on each defence
• identifying when justification defences (e.g. self-defence) apply, and when excuse-based defences (e.g. automatism, duress) apply
• the effect of successfully raising a general defence, the burden of proof, and the significance for liability

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which of the following is a justification defence in criminal law?
   1. automatism
   2. self-defence
   3. insanity
   4. intoxication

2. True or false? Voluntary intoxication provides a defence to any criminal offence.

3. Who bears the evidential burden of proof for raising the defence of self-defence?

4. What is the required test for non-householder self-defence in determining whether force was reasonable?

Introduction

General defences can excuse a defendant from criminal liability or justify the act itself. Key general defences include self-defence, intoxication, automatism, and insanity. For SQE2, you need to know the requirements for each, their practical scope, and how they affect criminal responsibility. Understanding these defences is essential for effectively evaluating criminal scenarios and advising clients.

General Justification and Excuse Defences

General defences apply to a wide range of criminal offences and can operate as either justification or excuse. Justification defences (such as self-defence) render the act lawful. Excuse defences (such as automatism or insanity) acknowledge wrongdoing but excuse the defendant because of their condition or circumstances.

Key Term: justification defence
A defence that, if established, renders the defendant's action lawful and removes criminal liability.

Key Term: excuse defence
A defence that, if established, recognises that the defendant's act was wrong but excuses them from liability due to their situation or capacity.

The Defence of Self-Defence

Self-defence, also called private defence, allows a person to use reasonable force to protect themselves, others, or property, or to prevent a crime.

Key Term: self-defence
A general defence available where a person uses reasonable force in the circumstances as they honestly believed them to be, for the protection of self, others, or property, or to prevent crime.

To rely on self-defence:

1. The force must be necessary on the facts as the defendant honestly believed them to be.
2. The force must be reasonable and not excessive in the circumstances.

Worked Example 1.1

Sophie is attacked late at night. She reasonably believes her attacker is armed. She strikes him with a bottle, causing injury.

Answer:
If Sophie honestly believed force was necessary, and the force was not excessive for her genuine belief, she may rely on self-defence—even if her belief was mistaken, provided it was honestly held.

Exam Warning

In self-defence, the reasonableness of force is assessed objectively but in the circumstances as the defendant honestly believed them to be, not as they actually were. An honest but unreasonable mistake may still allow the defence.

Intoxication as a Defence

Intoxication can impact liability only in certain cases.

Key Term: intoxication
A state resulting from voluntary or involuntary consumption of alcohol or drugs, sometimes affecting the defendant's mental state required for an offence.

• Voluntary intoxication is typically not a defence for crimes of basic intent where recklessness suffices for the mens rea. It may provide a defence to crimes of specific intent if, due to intoxication, the defendant did not form the required intent.
• Involuntary intoxication (where intoxication was not the defendant's fault) can provide a defence to both specific and basic intent crimes if the defendant did not form the required mens rea.

Key Term: specific intent offence
An offence where intention is the only form of mens rea that satisfies liability (e.g., murder, theft).

Key Term: basic intent offence
An offence where recklessness or intention is sufficient for liability (e.g., assault, criminal damage).

Worked Example 1.2

Ahmed gets very drunk and then punches a stranger, breaking his nose. He claims he was so intoxicated he did not intend harm.

Answer:
Voluntary intoxication is not a defence to basic intent offences like assault occasioning actual bodily harm, because recklessness (which is presumed by choosing to get intoxicated) suffices.

Exam Warning: Intoxication

Involuntary intoxication is only a defence where the defendant actually lacked mens rea at the relevant time. If mens rea is proved, intoxication (even if involuntary) does not excuse the defendant.

The Defence of Automatism

Automatism refers to situations where the defendant had no conscious control over their actions due to an external factor.

Key Term: automatism
A complete defence where a defendant's actions were wholly involuntary due to an external cause, so there is no actus reus.

Automatism differs from insanity, which involves an internal cause. If a defendant is acting in a genuinely automatic state caused by, for example, a blow to the head or a reaction to a drug, and was not at fault in putting themselves in that position, they are likely to be acquitted.

Worked Example 1.3

Carla suffers a seizure due to undiagnosed epilepsy and attacks someone, having no control or awareness at the time.

Answer:
If the seizure was due to an internal factor (like epilepsy), the correct defence is insanity, not automatism. If an external factor caused her loss of control, automatism may apply.

Key Term: insanity
A complete defence available where, due to a disease of the mind, the defendant was unable to understand the nature or quality of their act or that it was wrong.

Key Term: disease of the mind
A legal concept, not a medical diagnosis, referring to a malfunctioning of the defendant's mind caused by an internal condition.

Revision Tip

Always distinguish between automatism (external cause) and insanity (internal cause) when answering exam scenarios.

The Burden of Proof for General Defences

Generally, the defendant bears the evidential burden to raise a possible general defence. Once the defence is raised on the evidence, the prosecution must disprove it beyond reasonable doubt.

Key Term: evidential burden
The obligation on a party to adduce sufficient evidence to make a defence a real issue in the case.

Key Term: legal burden
The obligation on a party to prove an issue in the case to the required standard—usually the prosecution to prove guilt beyond reasonable doubt, unless a specific defence (e.g., insanity) places the legal burden on the defendant.

Exam Warning: Burden of Proof

For insanity, the legal burden is on the defendant to prove the defence on the balance of probabilities. For self-defence, the defendant has only the evidential burden; the prosecution must then disprove the defence beyond reasonable doubt.

Summary Table: General Defences Compared

Key Point Checklist

This article has covered the following key knowledge points:

• General defences include self-defence, intoxication, automatism, and insanity.
• Self-defence is a justification requiring necessity and reasonableness of force.
• Voluntary intoxication rarely provides a defence; involuntary intoxication only helps if D did not form mens rea.
• Automatism requires involuntary action due to an external cause, while insanity is due to an internal cause (disease of the mind).
• The burden of proof varies: for self-defence, automatism, and intoxication, the prosecution must disprove the defence beyond reasonable doubt when properly raised; for insanity, the defendant bears the legal burden on the balance of probabilities.
• Understanding the requirements and limits of general defences is critical for exam problem scenarios.

Key Terms and Concepts

• justification defence
• excuse defence
• self-defence
• intoxication
• specific intent offence
• basic intent offence
• automatism
• insanity
• disease of the mind
• evidential burden
• legal burden