The actus reus is the physical part of a crime, what the defendant does, fails to do, or causes. It refers to the external element of an offence, while the mens rea covers the mental element. To prove criminal liability, the prosecution must show that the defendant carried out the actus reus voluntarily and that it meets the definition set out in law.
The actus reus can take three main forms:
Conduct – where the act itself is criminal, such as driving while disqualified.
Circumstances – where the surrounding situation makes the act criminal, such as handling stolen goods.
Result – where a specific outcome must be caused, such as death in a charge of murder.
The act must usually be voluntary. If a person’s movement is completely involuntary, there is no actus reus.
Hill v Baxter [1958] – A driver who lost control due to being attacked by a swarm of bees would not be acting voluntarily.
Generally, there is no liability for doing nothing. However, a failure to act can form the actus reus if there is a legal duty to act. Legal duties arise in several situations:
Statutory duty – e.g. failing to provide a breath sample under the Road Traffic Act 1988.
Contractual duty – R v Pittwood [1902] (railway gatekeeper failed to close gate).
Duty through relationship – R v Gibbins and Proctor [1918] (parents failing to feed a child).
Duty taken on voluntarily – R v Stone and Dobinson [1977] (caring for an ill relative).
Duty from creating a dangerous situation – R v Miller [1983] (failing to deal with fire started accidentally).
Sometimes the actus reus is being in a certain condition or situation.
R v Larsonneur [1933] – The defendant was found guilty of being “found in the UK” unlawfully, even though she had been brought back involuntarily.
In result crimes, the prosecution must also prove that the defendant’s act caused the consequence (e.g. the victim’s death or injury). This involves both factual and legal causation, which are discussed separately on the causation page.