The actus reus includes only voluntary bodily movements, particularly one which society has an interest in preventing. This was confirmed by the Supreme Court in Powell v. Texas, 392 U.S. 514 (1968). Thus, if a defendant acted on reflex, then the defendant's conduct does not satisfy the actus reus requirement. Contrast this with mens rea, which refers to the criminal intent element of a crime.
Alternately, the actus reus requirement can also be satisfied by an omission. This is true only when the individual had a duty to act, and failed to act.
Generally, for the purposes of criminal liability, an individual may be under a duty to act if:
- A statute requires a person to act in a certain way.
- A contract requires a person to act in a certain way.
- Some special status relationship exists that creates a duty to act in a certain way (i.e. parental responsibilities).
- A voluntary assumption of care creates a duty to act in a certain way.
- The individual created the risk.