Actus reus is the act—or the omission or failure to act when there is a duty to act—that comprises the physical elements of the commission of a crime. The actus reus generally must be voluntary bodily movements that constitute a crime.
In contrast, mens rea (meaning “guilty mind”) is the criminal intent element of a crime. It is the intent to commit a crime, or the knowledge that the action, or failure to act when there is a duty to act, will result in the commission of a crime.

In Nevada, as in other jurisdictions, the concept of actus reus requires that a defendant has engaged in a voluntary act, or an omission when there is a legal duty to act, that constitutes the physical elements of a crime. This means that for a person to be found guilty of a crime, it must be shown that they actually engaged in behavior that is prohibited by law, such as stealing or causing bodily harm. The act must be a conscious and voluntary physical movement; involuntary actions, such as those conducted while asleep or unconscious, typically do not satisfy the actus reus requirement. On the other hand, mens rea refers to the mental state of the defendant at the time of the crime. Nevada law recognizes various levels of mens rea, ranging from intentional and knowing to reckless and negligent conduct. The presence of mens rea means that the individual had the intent to commit a crime or was aware that their actions could lead to a criminal outcome. Both actus reus and mens rea are typically required to establish criminal liability, although specific requirements may vary depending on the crime in question.