Criminology Actus Reus
Michelle Foster
  • LAST REVIEWED: 24 February 2021
  • LAST MODIFIED: 24 February 2021
  • DOI: 10.1093/obo/9780195396607-0294


Actus reus is an area of substantive criminal law and is an act by an individual that is deemed to be improper by societal laws. It is one of the elements of a crime and works in connection with mens rea or criminal intent. Illegal or immoral thoughts cannot be legally punished, but once those thoughts are put into action, there is a concurrence between the two elements. There are three types of actus reus, which include a voluntary act, possession, and omission. Within actus reus voluntariness is presumed on the part of the actor. If an accused party wishes to claim an action was involuntary, then an excuse defense would be necessary in criminal court. Possession is also a type of actus reus when an individual is in the possession of or has the possession of an item that is known by the individual to be illegal under the law. As an example, if a person is wearing a jacket that contains a bag of marijuana in the pocket and the person knows that the substance is illegal, then even if the marijuana is not the wearer’s marijuana, the action of possession is fulfilled due to the marijuana being an illegal substance. Omission is the third type of criminal act. Omission is satisfied when a person does not act when that person is required under law to do so. A person would be required to act when there is a contractual obligation to act or a duty to act, such as would be the case of a parent and a child. The parent has a duty to act to protect the child from harm. A defense to possession or omission is possible. Defenses include an alibi or an affirmative defense. A justification defense is one type of an affirmative defense where the accused party claims the action was not criminal given the circumstances of the situation such as duress, etc. An excuse defense is the second type of an affirmative defense in which the accused claims they should not be held accountable for the improper conduct for a reason such as age, intoxication, or insanity. Incomplete offenses, known as inchoate crimes, have their own section within criminal law but are treated similarly to completed offenses.

United States Code

The United States Code Title 18 is the area of law that outlines criminal behaviors and criminal legal procedures. Contained within the Code are all acts, along with the requisite mens rea, that have been outlawed in the United States by the United States Congress. The level and seriousness of each offense are included.

  • Federal US Code Title 18—Crimes and Criminal Procedure.

    Identifies criminal behavior and proper legal procedures for the United States. Sections within the Code are all areas of acts deemed to be improper.

back to top

Users without a subscription are not able to see the full content on this page. Please subscribe or login.

How to Subscribe

Oxford Bibliographies Online is available by subscription and perpetual access to institutions. For more information or to contact an Oxford Sales Representative click here.