Criminal statutes are drafted with an eye on ensuring the statute excludes legal conduct, provides forewarning to would-be criminals of potential liability, and differentiates between serious and minor offenses. These common elements for criminal statutes help carry out the policies for our criminal laws. Let’s take a closer look at the first requirement, that the statute excludes legal conduct.

To exclude legal conduct, the criminal statute must state what act or acts trigger criminal liability. Thus, there has to be some action on the part of the criminal defendant. This action is described using the term “actus reus” or “required act.”

Criminal law distinguishes between genuine human actions, which are susceptible of praise and blame, and mere events brought abut by physical causes which happen to involve a human body. This distinction is defined in terms of voluntary and involuntary acts. A voluntary act involves the use of the human mind; an involuntary act involves the use of the human brain, without the aid of the mind. With a voluntary act, a human being - a person - and not simply an organ of a human being causes the bodily action.

The Model Penal Code or MPC, which serves as a model for state legislatures in drafting criminal statutes, addresses this issue. The MPC provides that no person may be convicted of a crime in the absence of conduct that “includes a voluntary act of omission to perform an act of which he is physically capable.” It allocates to the prosecution the responsibility to persuade the fact finder beyond a reasonable doubt of the existence of a voluntary act. The MPC defines “act” as a “bodily movement whether voluntary or involuntary.”

This bedrock principle for all criminal statues is hard to define. This principle raises nettlesome questions as to what is voluntary and what is involuntary. The courts, and criminal statutes amended in response to court challenges, have tried to describe what acts are voluntary and involuntary. The resulting court cases are rather remarkable.

Here are some of the rulings and issues that have been considered by the courts:

• Habits or habitual action done without thought is usually treated as a voluntary action.
• Possession is a voluntary action only if the person is aware she has the thing she is charged with possessing (some courts hold it is sufficient if the defendant should have known).
• Acts of a hypnotized subject or a subject who is sleepwalking may not be a voluntary action.
• When a person who knows he is prone to epileptic seizures, operates a car on a public highway, has a seizure and kills people is a voluntary action even though the immediate action causing the harm was involuntary (the idea is the defendant knew he was likely to have the seizure and disregarded the consequences).
• Acts committed by an alternate personality in a person who has multiple personality disorder may be a voluntary act.
• Being drunk on a public highway only after the police take the drunkard from his house to the highway may not be voluntary for an offense that requires a voluntary act to be in public.
• A person shot by police and who acts unconsciously after the injury to kill the police officer may not be a voluntary act.

These issues address actions in the traditional sense of the term. The omission of failing to act can also be considered an act in some circumstances. Before we move on to another topic, let’s take a closer look at the criminal implications of omissions and failing to act.