Learning Outcomes
After working through this article, you will be able to identify and apply the core principles of criminal liability to specified criminal offences. You will understand the legal meaning of actus reus and mens rea, how these elements interact, and how omissions and causation can create or break liability. You will also be able to distinguish strict liability offences and explain their rationale in the context of the SQE2 exam.
SQE2 Syllabus
For SQE2, you are required to understand and apply the fundamental legal concepts which underpin criminal liability for specified offences. When revising this article, focus on being able to:
- differentiate and define actus reus and mens rea
- explain and apply the law on omissions and duties to act
- analyse the importance of causation—including when liability is interrupted by intervening acts
- describe strict liability and its boundaries.
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.
- Define actus reus and mens rea. How do they interact in establishing liability for a criminal offence?
- Explain how an omission can result in criminal liability. What are the key established duties to act?
- What test is used by the courts to determine legal causation, and how can the chain of causation be broken?
- What is strict liability, and why might Parliament create a strict liability offence?
Introduction
Understanding criminal liability for specified offences begins with comprehending the essential elements—actus reus and mens rea. These elements set the structure for applying criminal law to practical scenarios. In addition, omissions, causation, and strict liability can complicate how liability is imposed or broken. For SQE2, candidates must have a working knowledge of how these principles combine in real cases.
Elements of Criminal Liability
The prosecution must prove both a conduct element (actus reus) and a fault element (mens rea) for most offences, unless dealing with strict liability offences.
Key Term: actus reus
The actus reus is the external element of a criminal offence. It includes the defendant’s conduct, the circumstances, or a result required by the offence.Key Term: mens rea
The mens rea is the internal, fault-based element of a criminal offence. It encompasses the defendant’s intention, knowledge, recklessness, or (rarely) negligence.
Worked Example 1.1
A shoplifter picks up a sandwich intending to steal it, but then puts it back before leaving the shop. Is she guilty of theft?
Answer:
No. She formed the mens rea (intention to permanently deprive), but did not complete the actus reus (no appropriation—she did not leave with the property belonging to another). Both elements must be present at the same time.
Omissions and Duties to Act
Generally, criminal liability arises through positive acts, but failing to act can also establish liability where a duty exists.
Key Term: omission
An omission is a failure to act where the law imposes a duty to act, making the person potentially liable for resulting harm.Key Term: duty to act
A duty to act is a legal obligation, which may arise from relationships (parent–child), employment, assumption of care, creation of a dangerous situation, or statute.
Worked Example 1.2
Paula, a lifeguard, sees a child drowning but does nothing. Is she criminally liable if the child dies?
Answer:
Yes, Paula may be liable for manslaughter by omission because her employment gives her a duty to act. Failing to rescue the child when her duty required it results in liability if the omission causes death.
Revision Tip
Duties to act are limited—memorise the main categories for the exam: relationship, employment, assumption of care, creation of danger, or statute.
Causation and Intervening Acts
For result crimes, such as murder or actual bodily harm, causation links the defendant’s actions (or omissions) with the prohibited consequence.
Key Term: causation
Causation means proving that the defendant’s conduct was a substantial, blameworthy, and operative cause of the prohibited outcome.Key Term: intervening act (novus actus interveniens)
An intervening act is a new, independent event that significantly breaks the chain of causation and may relieve the defendant of liability for the ultimate result.
Worked Example 1.3
Craig stabs Sam lightly. In hospital, a doctor acts grossly negligently, causing Sam’s death. Is Craig liable for homicide?
Answer:
Possibly not. While Craig’s act was the factual cause, the grossly negligent medical care is an intervening act (novus actus interveniens) that may break the legal chain of causation if the original injury had substantially healed and the negligence alone caused death.
Exam Warning
Where an intervening act is claimed, analyse carefully if the defendant’s actions are still a significant, operative cause, or if later events are so independent and potent that liability is broken.
Strict Liability
Some statutory offences do not require proof of mens rea for some or all elements—these are strict liability offences. They are usually regulatory and punishable by fine.
Key Term: strict liability
Strict liability offences do not require proof of fault (mens rea) for at least part of the actus reus; liability attaches once the prohibited act or omission is proved.
Worked Example 1.4
A market trader sells food unfit for human consumption, honestly believing it is safe. Is she criminally liable?
Answer:
Yes, if the relevant statute creates a strict liability offence (common in public health law), her lack of fault is irrelevant—liability arises once the court finds she sold unsafe food.
Key Point Checklist
This article has covered the following key knowledge points:
- The elements of criminal liability are actus reus (prohibited conduct/circumstance/result) and mens rea (fault element).
- Both actus reus and mens rea must be proved for most offences; they must coincide in time.
- Omissions can result in liability where there is a legal duty to act; usual sources: special relationship, contract, assumption of care, danger creation, or statute.
- For result crimes, causation must be established—both factual (“but for” test) and legal (“substantial and operative” cause).
- The chain of causation can be broken by intervening acts (novus actus interveniens) if sufficiently independent.
- Strict liability offences require no proof of mens rea for at least some elements—commonly regulatory and aimed at protecting the public.
Key Terms and Concepts
- actus reus
- mens rea
- omission
- duty to act
- causation
- intervening act (novus actus interveniens)
- strict liability