Unit 7: Voluntary Act


  • Dressler 83 -99 (through 9.05[B])

  • Martin (CP)

  • Decina (CP)

Key words: 

  • voluntariness


A criminal offense requires both an actus reus (the physical component) and a mens rea (the mental component).

The actus reus is a voluntary act that causes a social harm.  It is an element of every offense, even when not explicitly listed in a statute.

The Voluntary Act

The act requirement can be satisfied by any bodily movement. Blinking, speaking, and pulling a trigger are all examples of an “act.” However, if A grabs B’s hand and moves it for B, then B has not acted. Furthermore, mere thoughts do not constitute an act.

An act is voluntary if it is willed — that is, the actor consciously decides to move a part of his body, and the movement of the body follows from that desire. Reflexes, spasms, epileptic seizures, and acts while asleep or unconscious are considered involuntary.  Habitual acts are considered voluntary.

Voluntariness in the context of the actus reus requirement is distinct from voluntariness in the context of affirmative defenses. Actions taken under duress or resulting from insanity are considered voluntary in the narrow actus reus context, but involuntary in the broader affirmative defense context. The distinction is important because the burden of proof is on the prosecution to establish the voluntary act and on the defendant to establish an affirmative defense.

Hypnotism could plausibly be considered an involuntary act, or a voluntary act with an involuntary defense. If the hypnotized defendant must follow the hypnotizer’s instructions, then the defendant could be equated to a sleepwalker, and therefore found to have acted involuntary. However, the hypnotized defendant could also be equated to a person under duress who willingly acts under suggestion, and therefore found to have acted voluntary.

A defendant who suffers from dissociative identity disorder (also called multiple personality disorder) has separate identities with separate memories and feelings. One of the defendant’s alternate personalities could voluntarily commit a crime that the defendant’s main personality had no control over. The few courts that have addressed the issue have found that the defendant acted voluntarily since one personality acted voluntarily.

Time Framing

Although a voluntary act is an implicit element of every offense, not every act leading to the offense need be voluntary. The defendant’s conduct need only include a voluntary act that is an actual and proximate cause of the social harm.

For example, if Jack knows that he suffers from epilepsy and drives a car, causing an accident, the voluntary act requirement may be satisfied. Although Jack did not have control over the seizure that caused the accident, he voluntarily decided to drive a car, knowing that doing so was dangerous given his condition. Similarly, if Jack voluntarily consumes drugs or alcohol, offenses that he involuntarily commits due to his intoxicated state will generally satisfy the voluntary act requirement.

Rationale for the Voluntary Act Requirement

The voluntary act requirement is better rationalized under retributivist principles than under utilitarian principles. Since involuntary acts are not a result of free choice, retributivists argue that involuntary actors are not morally blameworthy and do not deserve punishment.

Under utilitarian principles, involuntary acts may still warrant punishment. Society is better protected by punishing and segregating a person prone to frequent involuntary acts. Furthermore, punishing involuntary acts can also have a deterrent value. Although involuntary acts themselves cannot be deterred, the voluntary behavior leading to those acts can sometimes be deterred. For example, a person’s decision not to take medication is voluntary behavior that can be deterred, but a retributivist would not generally punish this decision.

In Robinson v. California, the Supreme Court used retributivist reasoning to invalidate a statute that criminalized drug addiction. The Court reasoned that it was cruel and unusual to criminally punish a person for her status, since status (like addiction) can be obtained innocently or involuntarily.

In Powell v. Texas, a plurality of the Supreme Court used utilitarian reasoning to uphold a statute that prohibited public intoxication. The Court distinguished Robinsonon the grounds that an alcoholic would not be criminalized for her status, but for appearing drunk in public. The Court reasoned that an alcoholic could benefit from the criminal punishment of the statute, since a brief stint in jail might be rehabilitative. Furthermore, the Court concluded that a broad reading of Robinson would be problematic: if an alcoholic acted involuntarily when she appeared drunk in public, then a drug addict could act involuntarily when possessing drugs or even when robbing a bank for money to buy drugs.

The Model Penal Code

MPC 2.01(1) requires a voluntary act for every offense, unless the offense is committed by omission. For omission liability, a defendant must have had a legal duty to act (2.01(3)) and must have been physically capable of performing the omitted act (2.01(1)).

MPC 2.01(2) lists examples of some involuntary acts, including reflexes, convulsions, movements during sleep or unconsciousness, and movements as a result of hypnotism. MPC 2.01(2)(d) defines conscious or habitual movements as voluntary.

Questions for Review:

Q1. Do you think hypnotism should be defined as a voluntary or involuntary act? What about acts by people with dissociative identity disorder? Support your answer.

Q2. Frank is a Vietnam veteran. When his wife, Janet, comes home from a business trip a day early, Frank is sleeping. Janet nudges him awake, and Frank grabs a knife from the bed side table and stabs her. Janet dies. Frank tells police officers that he did not mean to kill his wife, but that his actions were reflexive based on the way he was trained to fight in Vietnam. If you were the prosecutor, how would you argue that Frank’s actions were voluntary? What would you argue if you were the defense attorney?

Q3. Same facts as Q2, but Frank is not sleeping when his wife arrives home unexpectedly; instead, he is watching television. When he hears the door open, he grabs a gun from the end table and shoots her as she walked through the door. Does your argument change?

Of Possible Interest:

The New York Times recently featured a fascinating article titled “Can You Call a 9-Year-Old a Psychopath” that touches upon some of the themes discussed in this unit.