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.