Actus Reus
The physical element of a crime — the guilty act. It may consist of an act, an omission (where there is a duty to act), or a state of affairs. The actus reus must be voluntary.
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
CPS legal guidance pairs the concept directly with mens rea: a principal offender is someone who 'carries out the substantive offence i.e. performs or causes the actus reus of the offence with the required mens rea.' Where two or more people between them perform the physical elements of an offence, they can be joint principals.
Example
In CPS guidance on joint offending, 'D1 and D2 agree to commit a robbery. Each plays a part in carrying out the actus reus: together they attack and take money off security men making a cash delivery.' Both are liable as joint principals because each contributed to the physical act of the offence.
Related terms
Official sources
This explanation is drawn from the official sources below; every substantive statement is verified against them. For advice on a specific matter, see our find help page.