Actus Reus is the term used to describe not just a criminal act itself, but all of the circumstances and consequences that make the act a crime. In this article we look at what that actually means.

Whilst references to criminal law cases in this article are from the United Kingdom, most of the discussion is of principles that hold true across Western jurisdictions.

An accused must undertake voluntary action in order to be considered liable, and there are certain cases where acts are not considered to be voluntary:

• Automatism is where an individual is unaware, or not in control, of his actions
• Where an act is physically forced by someone else the act is not considered voluntary
• A reflex action can be used as a defense, for example, in the case of Hill vs. Baxter (1958) the defendant was stung by bees whilst driving and thus his dangerous driving was not voluntary
• Finally there are “State of Affairs” cases which have circumstance and consequences, but no acts. “State of Affairs” simply means the circumstances at a particular place and time. An act is doing something, such as killing somebody. An omission is not doing something, such as neglecting a dog. A state of affairs is just a set of circumstances, not necessarily in the control of the defendant. There are very few examples of such cases, and the only example most people can think of is the one of a drunk man escorted from a hospital by the police, and then charged with being drunk and disorderly in a public place – the poor fellow did nothing to cause the crime i.e. there was no act on his part (other than being drunk!)

If a defendant can prove that any of the circumstances or consequences that make up Actus Reus are missing then the court should find him innocent. We can look to the case of Deller in 1952 to understand how this works in practical terms. The defendant was found not-guilty of making a false representation to sell his car, because although the defendant thought that he was making a false representation he was in fact providing accurate information. His innocence was based on the fact that the circumstance that the representation he made was false was missing.

Not only does a consequence have to be demonstrated for a successful criminal prosecution, but also it must be shown that the defendant’s conduct caused the required consequence. For example a murder has the clear consequence of a dead person, but as a component of actus reus it must be shown that the defendant’s acts were a substantial cause of death.

Omission is a crime because common law places a burden on all of us to act in a particular way to our fellow man. For example:

• If you have a special relationship, such as that of parent-child, then neglecting to undertake certain duties can lead to a crime. In the case of Gibbins and Proctor (1918) a couple omitted to feed a child and were convicted of murder.
• The voluntary assumption of responsibility can create liability, for example, Stone and Dobinson (1977) took on the care of an elderly aunt and then failed to call medical services when she fell ill, which caused her death.
• A duty under contract place obligations on an individual that can create criminal liability when they are not met. In Pitwood (1902) the railway crossing keeper forgot to shut the gate which led to the death of a pedestrian, and he was found guilty of manslaughter.
• Non-compliance with statutory duties, such as the need to report traffic accidents within 24 hours, can lead to criminal offences.
• A defendant may have a duty due to prior conduct, for example, in the case of Miller (1983) the defendant woke up to a burning mattress and simply switched rooms and went back to sleep. The fact that he knew the house was on fire and he did nothing made him liable for murder.

Causation can be broken by an intervening act such as the actions of a third party. If this intervening act is sufficiently independent of the defendant’s act, and sufficiently serious, it can be said to break the chain of causation and thus eliminate the defendant’s liability. If the intervening act is simply a result of the defendant’s actions then no such break in the chain of causation has occurred, for example, switching of a life support machine does not cause a break.