THE ACTUS REUS MUST BE VOLUNTARY
The accused's conduct must be "voluntary" or "freely willed" if he is to incur liability. It may be involuntary for a variety of reasons:
AUTOMATISM
Automatism occurs where the defendant performs a physical act but is unaware of what he is doing, or is not in control of his actions, because of some external factor. See:
R v Quick [1973] 3 All ER 347.
REFLEX ACTIONS
Sometimes people can respond to something with a spontaneous reflex action over which they have no control. Although slightly different, this is sometimes classed as a form of automatism.
The classic example is that given in Hill v Baxter [1958] 1 All ER 193, of someone being stung by a swarm of bees while driving, and losing control of the car.
PHYSICAL FORCE
The conduct may be involuntary in that it is physically forced by someone else, in which case there will be no actus reus. See:
Leicester v Pearson [1952] 2 All ER 71.
"STATE OF AFFAIRS" CASES
One group of cases which cannot be discussed in terms of voluntary acts are often referred to as the "state of affairs" cases. These crimes are defined not in the sense of the defendant doing a positive act but consisting in the defendant "being found", "being in possession" or "being in charge" etc.
In some such cases all the prosecution needs to prove are the existence of the factual circumstances which constitute the crime - the existence of the state of affairs. See:
R v Larsonneur (1933) 24 Cr App R 74.
Winzar v Chief Constable of Kent (1983) The Times 28 March.
OMISSIONS
Can a person be held criminally responsible for a failure to act? The general rule is that there can be no liability for failing to act, unless at the time of the failure to act the defendant was under a legal duty to take positive action:
"Unless a statute specifically so provides, or … the common law imposes a duty upon a person to act in a particular way towards another … a mere omission to act [cannot lead to criminal liability]." (R v Miller [1983] 1 All ER 978.)
The difference between positive acts and omissions was highlighted in the Bland case [1993] 1 All ER 821, where the House of Lords held that euthanasia by means of positive steps to end a patient's life, such as administering a drug to bring about his death, is unlawful. However, withdrawing medical treatment, including artificial feeding, from an insensate patient with no hope of recovery when it was known that the result would be that the patient would soon die, is lawful if it was in the patient's best interests not to prolong his life.
A positive duty to act exists in the following circumstances:
(a) DUTY ARISING FROM STATUTE
Liability for failing to act will be imposed where the defendant can be shown to have been under a statutory duty to take positive action.
A leading example of such a case is provided by the Children and Young Persons Act 1933, which creates the offence of wilfully neglecting a child. Hence by simply failing to provide food for the child, or failing to obtain appropriate medical care, a parent could be held criminally liable for any harm that results. Another example is the Road Traffic Act 1988 which creates the offences of failing to provide a specimen when required to do so and failing to give a correct name and address when required to do so. See also:
Greener v DPP (1996) The Times, Feb 15 1996
(b) DUTY ARISING FROM A CONTRACT
Where a person is under a positive duty to act because of his obligations under a contract, his failure to perform the contractual duty in question can form the basis of criminal liability. See:
R v Pittwood (1902) 19 TLR 37.
(c) PUBLIC DUTY
A person in a public office may be under a public duty to care for others. See:
R v Dytham [1979] 3 All ER 641.
(d) VOLUNTARY ASSUMPTION OF RESPONSIBILITY/RELIANCE
There is a common law duty of care where there is a relationship of reliance between defendant and victim. Thus if someone voluntarily assumes responsibility for another person then they also assume the positive duty to act for the general welfare of that person and may be liable for omissions which prove fatal. See:
R v Stone and Dobinson [1977] 2 All ER 341.
(e) DUTY DUE TO DEFENDANT'S PRIOR CONDUCT
If the defendant accidentally commits an act that causes harm, and subsequently becomes aware of the danger he has created, there arises a duty to act reasonably to avert that danger. See:
R v Miller [1983] 1 All ER 978.
CAUSATION
When the definition of an actus reus requires the occurrence of certain consequences, the prosecution must prove that it was the defendant's conduct which caused those consequences to occur.
For example, in murder the prosecution must prove that the victim died; in section 18 of the offences Against the Person Act 1861 that the victim was wounded or caused grievous bodily harm; and in criminal damage that the property was destroyed or damaged.
There are two types of causation:
(a) Causation in Fact, for which the "But For" Test is used. See:
R v White [1910] 2 KB 124.
(b) Causation in Law, for which, for example in homicide cases, the defendant's act must be the "operating and substantial cause of death". See:
R v Smith [1959] 2 All ER 193.