---
title: "Actus Reus"
type: Legal Rule
source: https://casebriefly.com/legal-rules/actus-reus
---

# Actus Reus

Actus reus is the physical or voluntary act requirement for criminal liability. A defendant must commit a voluntary bodily movement, and mere thoughts, status conditions, or involuntary acts cannot form the basis of criminal punishment.

## Definition

Actus reus, Latin for "guilty act," is the requirement that a crime must involve a voluntary physical act or, in limited circumstances, a culpable omission. The principle serves as a fundamental safeguard against punishing mere thoughts, intentions, or a person's status. Under both common law and the Model Penal Code, criminal liability requires an act that is the product of the defendant's conscious will and effort.

An act is considered voluntary when it results from a conscious exercise of the will. Reflexive movements, convulsions, acts performed while unconscious or asleep, and conduct during a hypnotic state are generally not considered voluntary acts. Importantly, if a course of conduct includes even one voluntary act, the actus reus requirement is satisfied. The MPC defines an act broadly but excludes reflexes, movements during unconsciousness, and conduct during seizures from the definition of voluntary acts.

Omissions, or failures to act, can satisfy the actus reus requirement only when the defendant had a legal duty to act. Legal duties arise from statutes (such as filing tax returns), contractual obligations, special relationships (parent-child), voluntary assumption of care, or the creation of a peril. The actus reus requirement also prohibits status crimes under the Eighth Amendment, as the Supreme Court held in Robinson v. California that punishing a person for being an addict, rather than for the act of using drugs, constitutes cruel and unusual punishment.

## Elements

- A voluntary physical act or bodily movement
- The act must be the product of conscious will and effort
- Omissions satisfy actus reus only when a legal duty to act exists
- Status conditions alone cannot constitute actus reus
- At least one voluntary act within a course of conduct is sufficient

## Key Case

Robinson v. California, 370 U.S. 660 (1962)

## Landmark Cases

| Name | Citation | Significance |
| --- | --- | --- |
| Robinson v. California | 370 U.S. 660 (1962) | Held that criminalizing a status (drug addiction) violates the Eighth Amendment; punishment requires a voluntary act |
| Powell v. Texas | 392 U.S. 514 (1968) | Distinguished Robinson by allowing punishment for the act of public intoxication rather than the status of alcoholism |
| Martin v. State | 31 Ala. App. 334 (1944) | Held that appearing drunk in public was not voluntary when police carried defendant to a public place |
| People v. Newton | 8 Cal. App. 3d 359 (1970) | Recognized that an unconscious act (reflexive movement after being shot) is not a voluntary act |

## Exam Tips

- Always check whether the defendant's act was truly voluntary before analyzing mens rea
- For omission liability, identify the specific legal duty and its source (statute, contract, relationship, assumption of care, or creation of peril)
- Distinguish between involuntary acts and acts done under duress; duress involves a voluntary act compelled by threats and is analyzed as a defense

## Common Mistakes

- Confusing involuntary acts (reflexes, seizures) with acts performed under duress or coercion; duress involves a voluntary but coerced act
- Assuming a moral duty to act equals a legal duty; Good Samaritan liability requires a recognized legal duty, not just moral obligation
- Forgetting that possession can constitute an act if the defendant was aware of possession for a sufficient period to terminate it

## Mnemonic Or Memory Aid

"SCCRV" -- Statutes, Contracts, Creation of peril, Relationships, Voluntary assumption of care: the five sources of a legal duty to act

## Related Rules

- mens-rea-mental-states
- necessity-defense
- duress-defense
- involuntary-manslaughter

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Source: [Actus Reus — CaseBriefly](https://casebriefly.com/legal-rules/actus-reus)