Core principles of criminal liability - Definition of the of...

Learning Outcomes

After completing this article, you will be able to identify and explain the key elements required to establish criminal liability for any offence: actus reus, mens rea, and their interaction. You will be able to apply and distinguish conduct, circumstance, and result elements, and demonstrate an understanding of essential legal terms and principles such as causation, intention, recklessness, and the requirement for coincidence of actus reus and mens rea.

SQE2 Syllabus

For SQE2, you are required to understand the definition of a criminal offence and the core components of liability. In preparation for exam scenarios, focus your study on:

• The elements of a criminal offence—actus reus and mens rea—and their practical meaning
• The distinction between conduct crimes and result crimes
• The various forms of actus reus (acts, omissions, circumstances, results)
• The requirement of voluntariness for criminal liability
• Causation: factual and legal (imputable) causation, including intervening acts
• The main types of mens rea: intention, recklessness, and negligence
• The principle of contemporaneity: the requirement for coincidence of actus reus and mens rea 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. Define ‘actus reus’ and list its main components.
2. What is required to establish factual causation in a result crime?
3. Which of the following best describes ‘intention’ as a form of mens rea: (a) Motive or reason; (b) Foresight of a possible result; (c) Defendant's aim or purpose; (d) Any voluntary act?
4. Explain the rule of contemporaneity in relation to criminal liability.

Introduction

Establishing criminal liability requires precise identification and proof of two essential components: actus reus (the external element of the offence) and mens rea (the mental element). Both must be present for a defendant to be found liable, together with the absence of a valid defence. These requirements are the basis of all criminal offences and underpin how you must analyse any SQE2 problem question in criminal law.

Actus Reus: The External Element

Legal definitions of offences reveal that actus reus may consist of positive acts, failures to act (omissions), specified circumstances, and/or required results. The prosecution must prove every element of actus reus beyond a reasonable doubt.

Key Term: actus reus
The physical or external element(s) of a criminal offence—what the defendant did (or omitted to do), any required circumstances, and/or any result caused.

Conduct, Circumstances, and Result

Most offences require one or more of:

• Conduct: What the defendant does or fails to do.
• Circumstances: Specified surrounding facts (e.g., "property belongs to another" in theft).
• Result: A consequence, such as harm or death, that must follow from the conduct.

Some offences ("conduct crimes," such as dangerous driving) require only prohibited behaviour. Others ("result crimes," such as homicide) require proof of both certain conduct and a specific end result caused by the conduct.

Voluntariness

Criminally liable conduct must be voluntary—performed by a defendant acting with free will and control. Physically compelled acts (e.g., a person moved by another) do not meet this criterion.

Key Term: voluntary conduct
Behaviour over which the defendant consciously exercises control; criminal liability generally requires that the act or omission was voluntary.

Omissions and Duties

There is no liability for a mere omission unless the law imposes a duty to act. Duties arise in limited, established situations (e.g., statutory duties, contractual duties, special relationships, assumption of care, or creation of danger).

Key Term: omission
A failure to act, which can result in liability only if the defendant owes a recognised duty to act and the omission breaches that duty causing the result.

Causation

Result crimes require proof that the defendant's conduct in fact and in law caused the prohibited result. This involves both factual causation—was the result a direct consequence of the conduct?—and legal causation, which may be broken by intervening events that remove blame from the defendant.

Key Term: causation
The link between the defendant’s conduct and a prohibited result required by the offence; must show both factual ("but for") and legal (blameworthy and non-trivial) connection.

Key Term: factual causation
Also called "but for" causation; the prohibited result would not have occurred when it did but for the defendant's conduct.

Key Term: legal causation
The defendant’s conduct must be a substantial, blameworthy, and operating cause of the result; liability may be broken if an intervening act is sufficiently independent.

Worked Example 1.1

Rita set fire to an old mattress behind her flat. She left it smouldering, saw the fire spreading, but walked away without acting. The fire later destroyed a neighbour's property. Is Rita liable for criminal damage by omission?

Answer:
Yes, Rita created a dangerous situation and had a duty to take reasonable steps to avert the danger. Her failure to act is a culpable omission, and her conduct meets actus reus through the breach of that duty, which caused the damage.

Mens Rea: The Internal Element

The prosecution must prove the defendant’s blameworthy mental state when performing the actus reus. Mens rea varies by offence but commonly includes intention, recklessness, or (less frequently) negligence or knowledge.

Key Term: mens rea
The mental or fault element of an offence; the defendant's required state of mind at the relevant time.

Intention

Intention means the defendant acts purposefully, aiming for a particular consequence or result. Intention may also be inferred if the result of the conduct was virtually certain and the defendant appreciated this.

Key Term: intention
When it is the defendant’s aim or purpose to act or cause a result; may also be inferred where a result is virtually certain and the defendant realises this.

Recklessness

Recklessness means the defendant foresees a risk of harm and unjustifiably runs that risk. For SQE2, be aware that the test is subjective: Did the defendant actually foresee the risk?

Key Term: recklessness
Consciously taking an unjustified risk; defendant foresees a risk (of harm or result) and chooses to take it regardless.

Negligence

Negligence involves a failure to reach the standard of care a reasonable person would exercise in the same situation, leading to the prohibited harm. It is less common in criminal offences.

Key Term: negligence
Failing to take reasonable care, where the defendant ought to have appreciated a risk that a reasonable person would have observed.

Coincidence (Contemporaneity) Principle

Liability requires that actus reus and mens rea coincide in time—the defendant must have the required mental state when performing the act or omission. Where there is a continuing act or a single transaction comprising several acts, it is sufficient if the mens rea exists at any point while the actus reus occurs.

Key Term: contemporaneity (coincidence) principle
The requirement that the defendant’s actus reus and mens rea exist at the same time for criminal liability.

Worked Example 1.2

Ahmed pushed Kim, causing her to fall down stairs. He thought she was unharmed, but when he realised she was unconscious, he did nothing. Kim later died. Is there coincidence of actus reus and mens rea for liability?

Answer:
Liability exists if at any time while the harmful act or its consequences continued, Ahmed had the required mental state (e.g., intended or was reckless as to causing harm), even if not at the initial push. Ahmed’s inaction after realising her state may complete the actus reus as a continuing act or omission.

Exam Warning

Many offences require proof of a specific type of mens rea; do not assume that recklessness suffices where the law requires intention. For attempt, intention to commit the full offence is always required at the time of the act.

Revision Tip

Always analyse the precise components of actus reus, mens rea, and their timing for each offence in a scenario. Use the language of "conduct," "circumstances," and "result" to structure your answer and clearly state how each is met.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Actus reus and mens rea are the two core elements for criminal liability, both must be proven.
• Actus reus can include acts, omissions (where a legal duty exists), circumstances, and results.
• Criminal liability normally requires voluntary conduct.
• Causation (factual and legal) is needed where the offence requires a result.
• Mens rea may be intention, recklessness, or negligence, depending on the offence.
• Coincidence of actus reus and mens rea is required: they must exist at the same time.
• The absence of a valid defence is needed for criminal liability to follow.

Key Terms and Concepts

• actus reus
• voluntary conduct
• omission
• causation
• factual causation
• legal causation
• mens rea
• intention
• recklessness
• negligence
• contemporaneity (coincidence) principle