Actus reus
Actus reus is the “guilty act” — the physical element of a crime: the prohibited conduct, any required circumstances, and (for result crimes) the consequences. It can include an omission where the defendant was under a legal duty to act.
Last reviewed 14 June 2026
For result crimes the prosecution must prove causation: factual causation on the “but for” test (R v White) and legal causation, where the defendant's act must be a substantial and operating cause of the result.
Liability for omissions is exceptional and arises only where a duty to act exists — for example a contractual duty (R v Pittwood) or a duty created by the defendant's own dangerous act (R v Miller). The actus reus must generally coincide with the mens rea.
Key cases
- R v White [1910] 2 KB 124
- R v Miller [1983] 2 AC 161
- R v Pagett (1983) 76 Cr App R 279
Frequently asked questions
Can an omission be an actus reus?
Yes, but only where the defendant was under a legal duty to act — such as a contractual duty (R v Pittwood) or a duty arising from creating a dangerous situation (R v Miller).
What is the “but for” test?
The test for factual causation: would the result have occurred but for the defendant's act? If not, factual causation is established (R v White).
Related doctrines
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