Actus Reus

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blameworthy act it is used to denote the event on which a criminal offence is based.


In many cases the Actus Reus will be an explicit act (theft, assault, etc). In others it will be a prohibited state of affairs (e.g., having an offensive weapon (see: Offensive weapon) in a public place). In some cases the actus can be an omission to act (see: Omission), but usually only when the accused had a legal duty to act. Sometimes the actus may not be the event itself, but the effect it has on the victim (e.g., in rape), or the circumstances that surround it (e.g., bigamous marriage).

It is fundamental that the Actus Reus be a voluntary act; if a defendant could not have acted any other way (see: Automatism) then not only is he not liable, then the Actus Reus is deemed not have ocurred. Of course there will be the 'actus' part -- the action -- but it will not be 'reus'. In offences of Strict liability this is important, because in those offences the prosecution has no duty to show a Mens Rea (see: Mens Rea); thus an offence cannot be defended on the basis that there was no intention to comment the offence, but it can be defended on the basis that no offence was committed.

This defence will only be available if the defendant truly had no choice; for example, he was physically pushed by someone else. A defendant who makes a choice between two equally dreadful alternatives ('help us rob this bank or we'll shoot your wife') is not acting involuntarily in this sense, but he may have a General defence of Duress.

In order to be guilty of a crime two things must be proved

  • The defendant carried out the criminal act – the ‘Actus reus’ (The guilty act)
  • The defendant had a guilty state of mind – the ‘Mens Rea’ (The guilty mind)


Mike is very angry with Jim. Mike goes to Jim's house with the intention of attacking him with a baseball bat. However Jim isn’t in. Although Mike has the Mens Rea for the crime (the guilty mind) he doesn’t actually carry out the Actus Reus (the guilty act). Mike therefore cannot be guilty of an offence under the OAPA 1981, but may be convicted for the attempted offence, provided he has done acts that are more than merely preparatory.

The Actus Reus of a crime usually involves doing something.

The general rule is that an omission to act will not constitute the Actus Reus of a crime.

However there are (as you have just discovered) situations where an omission to act may amount to the Actus Reus of a crime.


To establish Actus Reus it is necessary to show;

  • The defendant’s conduct was the factual cause of the harm. This is simply know as the 'but for' test, as the victim would not have been hamed 'but for' the defendant's actions. This is shown in the case of Pagett (1983). Another case to look at is White (1910), where the defendant put arsenic in his mother's tea, intending to kill her, and claim his inheritance. His mother died of a heart attack before drinking the tea. As White did not cause the death, he could not be found guilty of murder and was found guilty of attempted murder.
  • The defendant’s conduct was in law the cause of the harm. It must be shown that the defendant's actions were the minimal cause of the consequences, shown in the cases of Cato (1976) and Kimsey (1996). A rule to this is the 'thin skull' rule. The rule is that the defendant must treat the victim as he or she finds them. For example, if the victim has a thin skull and is attacked by the defendant, the injuries will be more severe than injuries to a person with a normal skull. The defendant will be liable of the more severe injuries, although they were not foreseeable; Blaue (1975).
  • There was no intervening act which broke the chain of causation. There are three situations where an intervening act can break the chain of causation. These are: the victim's own act, an act of a third person, and a natural but unpredictable event. A victims own act must be one of the reasonable man, shown in the two similar cases of Roberts (1972) and Williams (1992). An act of a third person includes medical treatment. For medical treatment to break the chain of causation, it must be independent from the defendants act and inflicted injuries, and must also be 'potent and overwhelming' cause of the victims death. Cases include Smith (1959), Cheshire (1991) and Jordan (1956).