One of the most important aspects of actus reus is that the criminal actions that occurred were voluntary. Under criminal laws an individual cannot be convicted of a crime if the illegal behavior was committed involuntarily. If the criminal activities that took place were involuntary, then actus reus did not occur.
Criminal laws recognize actus reus as one of the primary and essential elements of a crime that are necessary to impose criminal liability upon an offender. Without actus reus, a crime was not committed, and therefore, the individual who was responsible for the behavior that is in question cannot be punished for any harm that resulted.
Many people question how criminal activity can be involuntary. When an individual takes part in actions or behaviors, he or she is choosing to do so. However, there are some instances in which an individual may take part in activities over which he or she had no control. Though these occurrences are rare, they do occur. Criminal laws and legal precedents have been established to acknowledge the lack of criminal intent and liability in these cases.
Criminal laws recognize that in rare cases an individual may take part in harmful and detrimental activities without any intent or knowledge of the damage that he or she is causing.