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 Hawaii, as in other jurisdictions, the concept of actus reus requires a voluntary act, or an omission to act when there is a legal duty to do so, that leads to the commission of a crime. This act must be a physical element of the crime, such as taking property in theft, or striking a person in an assault. Without actus reus, there can be no criminal liability. Mens rea, on the other hand, refers to the mental state of the defendant at the time of the crime. It involves an individual's intention to commit a crime or their knowledge that their actions or omissions, when there is a duty to act, would lead to the commission of a crime. Hawaii law requires both actus reus and mens rea for a conviction in most criminal cases, ensuring that both the physical act and the individual's intent are considered in determining criminal responsibility. Specific statutes in Hawaii will define the necessary mens rea for different crimes, which can range from intentional and knowing to reckless or negligent conduct.