The actus reus — sometimes called the external elements of a crime — is the Latin term for the "guilty act" which, when proved beyond a reasonable doubt in combination with the mens rea, i.e. the "guilty mind", produces criminal liability in common law-based criminal law jurisdictions such as the United States, Australia, Canada, and the United Kingdom.

Actus reus - Concepts

The terms actus reus and mens rea are derived from the principle stated by Edward Coke, namely, actus non facit reum nisi mens sit rea,1 which means: "an act does not make a person guilty unless (their) mind is also guilty", i.e. the general test is one that requires proof of fault, culpability or blameworthiness both in behaviour and mind. In this respect, the role of automatism is highly relevant in providing a positive explanation of the need to demonstrate the voluntariness of the behaviour for it to found liability. Once the actus reus has been established in a conventional offence, there must be a concurrence of both actus reus and mens rea to justify a conviction. Most legislatures also create so-called strict liability offences, which criminalise the behaviour without the need to prove a mens rea. The majority of these offences are either quasi-criminal or relatively low fault instances of behaviour, but liability may still be negated if automatism is present.
The actus reus of a crime generally falls within one of three classes, the first two being subject to a requirement of causation. The definition of each offence, whether common law or statutory, will always include the factual components necessary to constitute the actus reus. Some of these facts will be:
  1. Contextual, i.e. describing the time or general circumstances during which the key components were allegedly committed, e.g. that a vehicle was driven at night with defective lights or that injuries were caused while resisting lawful arrest;
  2. The key elements considered sufficiently antisocial that they should be proscribed, e.g. driving a vehicle dangerously. This will usually be based on one or more verbs which describe what the accused must have done.
  3. Consequential, i.e. describing the result or outcome of the verb(s), e.g. that a victim was injured or suffered loss in some material way.

Actus reus - Act

For both common law and statutory offences, establishing the detailed list of elements necessary to constitute the offence and their scope is a matter of interpretation which may require the courts to review and revise its precedents to ensure that the current interpretations match the current needs. For example, if an offence uses a verb such as "inflict" or "enter", it is for the courts to lay down the factors by which to distinguish the forms of action that might satisfy the requirement. Burglary requires "entry as a trespasser" so if the accused cut a hole in a window and introduced a fishing rod into the room to catch jewellery, would this be an entry? Equally, if a surgeon performs a lifesaving operation knowing that the accused did not consent, did he or she inflict injury by cutting open the patient as victim with a knife? At times, these decisions will have profound moral and practical implications for a society, with the rulings of judges and the findings of juries reflecting prevailing attitudes on issues as controversial as euthanasia and assisted suicide, sexual relationships, and the various forms of business activities that should or should not be crimes. The problem is that, in effect, the courts may retrospectively criminalise behaviour. If there are justifications for this outcome, they follow the argument that a person skating on thin ice can hardly complain if he or she falls through. It is the function of the courts to act to protect the rights of victims and the needs of society at large, and if this means that courts have an inherent jurisdiction to create new crimes by reinterpreting the old, that is probably a price worth paying so long as the power is used sparingly.
Taking a more everyday example, most legislatures create offences which regulate road traffic. Although humans and the words used to require a test of whether particular driving was or was not dangerous have remained remain relatively unchanging, technology has steadily evolved. Many cars are now fitted with sophisticated computerised systems to help control the vehicle while braking and so reduce the risk of skidding. If a car does skid and injures a pedestrian because, in all the circumstances, it was travelling at an excessive speed, should there be a variable test of dangerousness depending on whether the particular car was fitted with one or more of the additional safety devices? The difficulty is that the speed at which it would be dangerous to drive an unmodified car might be entirely safe in the same road conditions in a car with the relevant devices installed. The answer is that each court will make a decision based on the particular set of facts before it but will always require a certain minimum level of skill from the driver. Hence, an inexperienced driver cannot use the lack of skill as an excuse. Conversely, whether a person with vast experience as an international rally driver should show a greater than average level of skill in ordinary driving conditions is usually only a matter to be considered in sentencing.
"Driving" is a conduct element but some offences require that a particular result be obtained by the conduct, e.g. that the behaviour "annoyed", "offended", "outraged", "obstructed" or "endangered" one or more identifiable individuals (see criminal jurisdiction where the terminatory theory is based on the prohibited consequences occurring within the territory of the court)..

Actus reus - Omission

See main article omission (criminal)

Actus reus - State of affairs

A number of offences are defined as a situation or context, e.g. "being found within enclosed premises", "being drunk in charge of a motor vehicle", etc. These are usually strict liability and a conviction could be sustained even though an accused did not act in a wholly voluntary manner. Hence, if a person fell asleep in a quiet corner of a library and was locked in by inadvertent staff, the offence would be committed, but the relatively low level of fault could be reflected in the sentence. In Martin v State (1944) 31 Ala App 334 17 So 2d 427. Martin was arrested at home and taken onto the highway by police officers, where he showed signs of being drunk. His conviction for being drunk on a public highway was quashed because his arrival on the highway was not voluntary. Whereas in R v Larsonneur (1933) 24 Cr. App. R. 74 Larsonneur, a French citizen, was served with an order requiring her to leave the UK and not return. Instead of returning to France, she travelled to Ireland, and was deported back to England where she was arrested for "being found in the United Kingdom". The Court of Criminal Appeal held that the involuntary circumstances under which she was returned were "perfectly immaterial". In Winzar v Chief Constable of Kent (1983) The Times, 28 March 1983. where the charge was one of being "found drunk on a highway" contrary to s12 Licensing Act 1872, Winzar had originally been found drunk in a hospital and asked to leave. When he failed to do so, police officers removed him to their patrol car, which was parked on the highway outside, and then charged him with the offence in question. Upholding the conviction, Goff LJ pointed out that a distinction would otherwise have to be drawn between the drunk who leaves a restaurant when asked to do so and the drunk who is forcibly ejected after refusing to leave. If both are arrested in the street shortly afterwards, it would be wrong for the courts to regard the former as guilty and the latter as not. But the U.S. approach of abuse of process might prevail if the police were to drag a person from his own bed and into the street before charging him with being found drunk on a highway.