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 Mississippi, as in other jurisdictions, the concept of actus reus requires that a defendant must have engaged in a voluntary act, or an omission when there is a legal duty to act, that constitutes the physical element 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 property or physically harming another person. The act must be a conscious and voluntary physical movement. Involuntary actions, such as those conducted while unconscious or during a convulsion, are generally not considered actus reus. On the other hand, mens rea refers to the mental state of the defendant at the time of the crime. It involves an individual's intent or knowledge that their conduct is criminal. Mississippi law recognizes various levels of mens rea, from intentional and knowing acts to reckless or negligent behavior, depending on the crime. Both actus reus and mens rea must be established for a defendant to be convicted of most crimes, ensuring that both the physical act and the requisite mental state are proven beyond a reasonable doubt.