Concept
Involuntary Movements
Acts and omissions
Involuntary Movements
Subsection (1) of § 2.01 demands a voluntary act but never says what makes an act voluntary. Subsection (2) fills that gap from the opposite direction. It introduces a list of movements that are not voluntary acts within the meaning of the section.1 The technique is practical because it spares courts from deciding what the will is, or whether a person wills each step in a walk across a room. A court asks only whether the movement before it falls into one of the listed categories, so a voluntary act for criminal law purposes is simply an act that is not involuntary.2
What the four share is that the person whose body moved did not choose or control the movement. The fourth category, a residual catch-all, shows the common thread most clearly. It covers the classic case in which one person physically forces another's body into motion, as where A by force causes B's body to strike C, and it reaches a defendant who could not control the muscles after being tased.4 In neither case did the person who moved choose the movement, which is why the Code withholds the label voluntary act.
The list is narrow, and the narrowness matters on fact patterns that feature intense pressure. A person who acts because of a threat of death or serious injury, to avoid a greater harm, or because of serious mental impairment still performs a voluntary act, since that person chose among options even if every option was bad.5 Whether such a person is punished then depends on whether a justification or excuse defense is available. The residual category likewise leaves out so-called brainwashing, which changes attitudes through coercive persuasion, the ingestion of drugs or alcohol, and the irresistible impulse that some jurisdictions treat under the insanity defense.6 The division of labor follows the question each doctrine asks. The act element asks a yes-or-no question about control over the movement itself. Defenses ask whether the pressure was grave enough to justify or forgive the choice, and folding pressure into the act element would let every pressured choice skip that second inquiry.
Because pressure does not make a movement involuntary, the sound order of analysis on an exam fact pattern is to ask first whether the body moved without the person's choice, and to turn to defenses only if it did not. The four categories follow in order, beginning with the most familiar one, reflex and convulsion.
Reflex or Convulsion
The first of the four categories in § 2.01(2) is the easiest to state: a reflex or convulsion is not a voluntary act.9 The two words describe different movements. A reflex is a muscular reaction "in which the mind and will have no share," such as a knee jerk or the blinking of an eyelid.10 A convulsion covers the spasms and seizures in which muscles fire without any choice by the person, an epileptic seizure being the familiar example.11 What the two share is the absence of any decision. The movement occurs in the person's body without being the person's own conduct, and that is why the Code removes it from the category of acts that can carry criminal liability.
The reason lies in how punishment works. A penalty operates by attaching a cost to a choice, so that people choose differently the next time. A person in the grip of a seizure has no choice for that threat to act upon, and the arm would have jerked whatever the penalty for striking someone. Punishing the movement would therefore inflict suffering without deterring anything, and it would condemn a person for a bodily event that expresses no decision at all. The act requirement exists to mark off conduct a person controlled from events that merely happen through the person's body, and a reflex or convulsion falls on the second side of that line.
The consequence shows up in the elements. Section 2.01(1) requires that liability rest on conduct that includes a voluntary act, so the prosecution must prove at least one voluntary act beyond a reasonable doubt.12 When the only movement tied to the harm is a convulsion, nothing the defendant did at the moment of harm can satisfy that demand. The case then fails at the act element, before anyone asks what the defendant intended or knew. Jane's foot and hands in the café example are this rule at work: her limbs moved, but the movement was a spasm and not her act.
The pair differs in one variable only, which is whether the arm's movement was chosen. Everything else that might seem to matter, including the seriousness of the injury and the victim's innocence, stays constant and does not change the answer on the act element.
The category has a boundary that exam fact patterns exploit. Students lose points here when they treat speed alone as the mark of a reflex. A reflex is defined by the absence of mind and will, and the speed of a reaction does not settle that question. A person who finds themselves about to fall and reaches out to seize a nearby object has not reflexed, because the mind quickly grasped the situation and dictated the movement.13 That grab is fast but chosen, so it is a voluntary act and the analysis proceeds to the other elements. A knee that kicks out when a physician taps it with a hammer moves the same kind of limb with no decision behind it, and that movement is a reflex.
Freedom from liability for a convulsion attaches to the convulsive movement itself. A person who knew of a seizure disorder or a tendency to faint, and chose to act anyway, presents a different question, because the law can look past the involuntary moment to a voluntary act earlier in the same course of conduct.14 The next section takes up that doctrine. For now the point is that a convulsion standing alone as the source of the harm supplies no act.
Unconsciousness or Sleep
The second category in § 2.01(2) removes "a bodily movement during unconsciousness or sleep" from the class of voluntary acts.17 Two situations fall within that phrase. The first is ordinary sleep, in which a person gets up and moves about, as a sleepwalker does. The second is true unconsciousness, in which the body keeps making coordinated movements while the person has no awareness of them, behavior often described as automatic. The question in both is when the person was asleep or unconscious: if the body moved during that state, the movement cannot carry criminal liability, however harmful it turned out to be.
The reason connects to the purposes the act requirement serves. Punishment works by attaching a cost to a choice, so that people choose differently the next time, and a sleeping or unconscious mind makes no choice for that cost to influence. Utilitarians therefore see nothing to deter in involuntary behavior, and retributivists see no one who chose a wrongful act and so no one who deserves blame for it.18 Society is not left defenseless, because other systems of care and control, such as involuntary hospitalization, exist for people who pose an ongoing threat through involuntary conduct.19 Both accounts of why the criminal law withholds punishment from involuntary acts apply to this category without modification: a person asleep has no decision to deter and no wrongful choice to condemn.
The sleepwalking example shows how this category sits alongside the elements of an offense. The Code defines an act as a bodily movement, whether voluntary or involuntary, and it breaks the conduct side of an offense into conduct, circumstance, and result.20 A woman who sleepwalks out of her house and into a neighbor's home presents every one of those: her walking is the conduct, her presence inside another person's dwelling is the circumstance, and the trespass is the result. Even so, no actus reus is established, because the walking occurred during sleep and so was not a voluntary act.21 Two filters are at work here. The first asks whether the facts match the material elements the offense describes, and the second asks whether the person controlled the movement that produced them. A fact pattern can clear the first and fail the second, which is why a checklist of elements that ignores voluntariness would convict a sleepwalker whom the Code protects.
This category is narrow, and the narrowness has a reason. Courts find unconsciousness only rarely, because the exclusion covers a person who was asleep or unconscious at the moment of the movement, and a gap in memory does not show that. Amnesia is a fact about what the person retains afterward, while the exclusion concerns what the person was doing when the body moved. A defendant who acted while conscious and cannot later recall it was still acting in the moment, so forgetting is different from not acting. The line also guards against fabricated claims. A claim of unconsciousness rests largely on the defendant's own account of an inner state that others can seldom verify, and if a bare assertion of lost memory sufficed, every defendant would have a reason to make it. Requiring that the movement itself have occurred in sleep or unconsciousness keeps the exclusion for the cases that fit it.
On an exam stem, the point most often missed is that memory loss is not unconsciousness. The analysis asks whether the person was asleep or unconscious when the body moved, and a later inability to recall the episode answers a different question unless other facts show the person lacked awareness at the time. A defendant's choices before falling asleep or losing awareness can raise a separate issue, which the discussion of earlier voluntary conduct takes up below.
Hypnosis
The third category in § 2.01(2) reaches "conduct during hypnosis or resulting from hypnotic suggestion," and the Code treats that conduct as not a voluntary act.24 The two phrases cover two different moments. Conduct during hypnosis is movement while the subject is in the hypnotic state, and conduct resulting from hypnotic suggestion reaches later behavior that carries out an instruction planted during a session, even after the trance has ended. In both situations the Code asks one question, which is whether hypnosis lies behind the movement. It does not ask how hard the subject tried to resist, and it does not ask whether the act was one the subject would ordinarily find repugnant.
The Code's categorical treatment stands out because the common law has not settled the point. There is real controversy over whether behavior during hypnosis is voluntary or involuntary.25 The disagreement traces to differing views on whether a hypnotized person will perform acts that the person finds repugnant.26 If a hypnotized person would refuse such acts, the person keeps some control and the conduct looks willed. If the person would not refuse, hypnosis has displaced the person's own control over the body. Because that question is contested, common-law courts are divided, and a court in a jurisdiction that has not adopted the Code may treat hypnotized conduct as a voluntary act.
The Code answers the uncertainty with a bright line, and the reasoning has two parts. The first part is that, if hypnosis overrides the person's control over movement, the conduct reflects no choice, so the reasons for withholding punishment from other involuntary movements apply here too: a penalty has no decision to deter, and there is no wrongful choice to condemn.27 The second part is practical. A case-by-case rule would require a factfinder to decide how completely hypnosis displaced control in each case, which is the very question on which informed views differ. A categorical exclusion gives certainty that such an inquiry could not.
The two versions differ in one variable, which is the governing rule. The conduct, the injury, and the hypnotic suggestion are the same, so the contrast is the entire lesson. On an exam stem the usual error is to write that hypnotized conduct is always involuntary, which overstates the law, because the Code's rule is categorical while the common law is divided. The first step is therefore to identify which approach the jurisdiction follows, and only an MPC jurisdiction supplies the automatic answer.
Other Non-Willed Movements
The fourth category in § 2.01(2) is a catch-all. After listing reflex or convulsion, unconsciousness or sleep, and hypnosis, the Code reaches any "bodily movement that otherwise is not a product of the effort or determination of the actor, either conscious or habitual."30 The first three categories name particular states of body or mind, while this one asks the underlying question directly: whose effort or determination produced the movement? If the actor's own did not, the movement is not a voluntary act, whatever label fits it. The Code can use such open wording because it never defines voluntariness in the affirmative. It lists kinds of involuntary movement, and a voluntary act is simply one that is not involuntary.31
The clearest movement the catch-all reaches is one produced by another person's physical force. When A by force causes B's body to strike C, B has performed no voluntary act, because B's body moved without B's effort or determination.32 The same is true of a person shoved off a dock: the plunge into the water is not the victim's act.33 A defendant who loses control of the muscles after being tased is in the same position.34 In each of these situations the moved person serves as an instrument for someone else's conduct. The reasons behind the other involuntary categories carry over directly. A penalty works by attaching a cost to a choice, and a person whose body is moved by someone else made no choice for the penalty to influence, so there is no wrongful decision to condemn.35 The person who applied the force is the one whose conduct the criminal law can examine.
A decided case shows the rule at work. In Martin v. State an intoxicated man was arrested at his home and taken by officers onto the highway, where he used loud and profane language, and he was convicted under a statute that punished an intoxicated person who appears in a public place and manifests drunkenness by boisterous conduct or profane speech.36 The Alabama Court of Appeals reversed, reasoning that the statute presupposes a voluntary appearance and that the charge cannot be proved by showing that the accused was involuntarily and forcibly carried to the public place by the arresting officer.37 On that reasoning the defect lay in the element of appearing in public, because the officers rather than the defendant supplied that movement. The case is a standard illustration of the voluntary act requirement, and physical control by another person appears among the most commonly cited examples of involuntary action.38
The words "either conscious or habitual" do separate work. They tell the reader that the effort or determination behind a movement need not take the form of a deliberate decision made at that instant. A voluntary act can result from habit or even inadvertence, so long as the person could have behaved differently, which is why a parent who drives to a child care center out of habit, or while daydreaming, has acted voluntarily.39 The reason is practical. Almost all ordinary conduct, such as walking, steering, and typing, proceeds without a fresh decision for each movement, and a rule demanding that kind of decision would place most everyday conduct outside the criminal law. A habit stays the actor's own because the actor's mind formed it and can redirect it, whereas a reflex is a reaction in which the mind and will have no share.40
The catch-all also has edges. It does not cover brainwashing, a person's ingestion of drugs or alcohol, or the "irresistible impulse" situation that some jurisdictions treat under the insanity defense.41 In each of those situations the person's own mind, however influenced, still directs the person's own movement, so the movement remains the actor's product and any relief has to come from a defense rather than from the absence of an act. The most common boundary on an exam is the line between force and threat, and it follows the same logic. A person who moves in response to a threat of death or serious injury still chooses to move, however unwillingly, and the criminal law generally treats that movement as voluntary. Whether the person is punished then depends on the separate defenses of justification or excuse.42 Duress is taught elsewhere, and the only point here is what a threat fails to do, which is remove the act.
Students lose this issue when they treat a threat as if it were physical force. Force takes the choice away from the person whose body is moved, while a threat leaves the choice in place and makes it a hard one. Because the catch-all turns on the source of the movement, it is best run as a short series of questions applied to each movement the offense requires.