Elements of a Crime - Actus Reus

Each crime is normally composed of two elements: the wrongful act which is known as the actus reus and the guilty mind which is referred to as mens rea.

The actus reus compromises all the elements of a crime except for the mens rea.

Each crime has its own actus reus laid down in either statute or common law. In order to establish guilt, all parts of the actus reus must be committed. 

for example: Grievous Bodily Harm contrary to S.18 of the Offences Against The Person Act 1861 has an A.R of unlawful wounding or causing GBH to another.  

In almost all cases the voluntary actions of the defenant (D) will constitute the AR.
A case in support is Hill V Baxter where there was no A.R

Definition of voluntary actions: a concious, deliberate movement of the muscles.

Accordingly, the D must be conciously in control of his actions.
However, there are different types of offence with different ways of achieving the A.R:

1.Conduct Crimes: where the conduct (behavious) of the D is the AR eg. lying under oath in perjury

2.Result or Consequence Crimes: that require the D's conduct to result in something that is prohibited. eg. in murder the result of D's unlawful act or omission is the death of another human being. All of this is the AR.

3.State of Affairs Crimes: which are rare but will mean that D is guilty of an offence merely by being in a particular place when that particular state of affairs is prohibited. eg. R v Larsonneur

Normally a D will not be guilty for failing to do something
ie. thus no one will be guilty for failing to save a drowning person he does not have responsibility for.

There are exceptions to this rule though where the D will have a duty to act:

1. Where a statute creates a liability for omissions
eg. failing to provide a specimen of breath as required  or failing to stop after an accident under the Road Traffic Act 1988

2. Where there is a contractual duty to act
eg. a lifegaurd