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Criminal Law
Wayne State University Law School
Dillof, Anthony M.

Common Law


Actus Reus = Conduct (+ harmful result)
– Voluntary act (“willed movement”) or omission
– if unconscious è not responsible
– Reflex isn’t voluntary act

Mens Rea
§ 5.01 Common Law Principle and Definition

Simply put, “mens rea” refers to the mental component of a criminal act. However, there is much ambiguity inherent in this term. The doctrine has been defined in two basic ways:

[A] “Culpability” Definition of “Mens Rea” – In the early development of the doctrine, many common law offenses failed to specify any mens rea. Mens rea was defined broadly in terms of moral blameworthiness or culpability. Thus, at common law and in jurisdictions that still define the doctrine broadly, it was and is sufficient to prove that the defendant acted with a general culpable state of mind, without the need to demonstrate a specific state of mind such as “intentionally,” “knowingly,” or “recklessly.”

[B] “Elemental” Definition of “Mens Rea” – Much more prevalent today is a narrow definition of mens rea which refers to the particular mental state set out in the definition of an offense. In this sense, the specific mens rea is an element of the crime. Note that a person can be culpable in that he was morally blameworthy yet lack the requisite elemental mens rea.

§ 5.02 Specific Mens Rea Requirements

[A] “Intentionally” – A person “intentionally” causes the social harm of an offense if: (1) it is his desire (i.e., his conscious object) to cause the social harm; or (2) he acts with knowledge that the social harm is virtually certain to occur as a result of his conduct.

The doctrine of “transferred intent” attributes liability to a defendant who, intending to kill (or injure) one person, accidentally kills (or injures) another person instead. The law “transfers” the defendant’s state of mind regarding the intended victim to the unintended one.

[B] “Knowingly” or “With Knowledge” – Sometimes, knowledge of a material fact – an attendant circumstance – is a required element of an offense. A person has “knowledge” of a material fact if he is aware of the fact or he correctly believes that it exists. Most jurisdictions also permit a finding of knowledge of an attendant circumstance when the defendant is said to be guilty of “wilful blindness” or “deliberate ignorance,” i.e., if the defendant is aware of a high probability of the existence of the fact in question, and he deliberately fails to investigate in order to avoid confirmation of the fact. An instruction in this regard is sometimes called an “ostrich instruction.”

[C] “Wilfully” – “Wilful” has been held in different jurisdictions to be synonymous with other terms, e.g., “intentional,” “an act done with a bad purpose,” “an evil motive,” or “a purpose to disobey the law.”

[D] “Negligence” – Criminal negligence (as opposed to civil negligence) ordinarily requires a showing of a gross deviation from the standard of reasonable care. A person is criminally negligent if he takes a substantial, unjustifiable risk of causing the social harm that constitutes the offense charged.

Three factors come into play when determining whether a reasonable person would have acted as the defendant did:
(1) the gravity of harm that foreseeably would result from the defendant’s conduct;
(2) the probability of such harm occurring; and
(3) the burden to the defendant of desisting from the risky conduct.

[E] “Recklessness” – A finding of recklessness requires proof that the defendant disregarded a substantial and unjustifiable risk of which he was aware.

[F] Distinction Between Negligence and Recklessness – The line between “criminal negligence” and “recklessness” is not drawn on the basis of the extent of the defendant’s deviation from the standard of reasonable care — the deviation is gross in both cases — but rather is founded on the defendant’s state of mind. Criminal negligence involves an objective standard – the defendant, as a reasonable person, should have been aware of the substantial and unjustifiable risk he was taking); recklessness implicates subjective fault, in that the defendant was in fact aware of the substantial and unjustifiable risk he was taking but disregarded the risk.

[G] “Malice” – A person acts with “malice” if he intentionally or recklessly causes the social harm prohibited by the offense.

General and Specific Intent

[A] Specific Intent – Generally speaking, a “specific intent” offense is one in which the definition of the crime:
(1) includes an intent or purpose to do some future act, or to achieve some further consequence (i.e., a special motive for the conduct), beyond the conduct or result that constitutes the actus reus of the offense, e.g., “breaking and entering of the dwelling of another in the nighttime with intent to commit a felony”; or
(2) provides that the defendant must be aware of a statutory attendant circumstance, e.g., “receiving stolen property with knowledge that it is stolen.”

[B] General Intent – An offense that does not contain one of the above features is termed “general intent,” e.g., battery, often defined statutorily as “intentional application of unlawful force upon another.” This is a general-intent crime, for the simple reason that the definition does not contain any specific intent beyond that which relates to the actus reus itself. The only mental state required i

’s risk-taking is inadvertent.

Voluntary Act
[A] General Rule – Subject to limited exceptions,a person is not guilty of a crime unless his conduct includes a voluntary act.Few statutes defining criminal offenses expressly provide for this requirement but courts usually treat it as an implicit element of criminal statutes.

[B] Definitions

“Act” – An act involves physical behavior. It does not include the mental processes of planning or thinking about the physical act that gives rise to the criminal activity (such is the domain of mens rea).

“Voluntary” – In the context of actus reus, “voluntary” may be defined simply as any volitional movement. Habitual conduct – even if the defendant is unaware of what he is doing at the time – may still be deemed voluntary. Acts deemed involuntary may include: spasms, seizures, and bodily movements while unconscious or asleep.

[C] Burden of Proof – Although a defendant may raise as a defense that his conduct was not voluntary, the voluntariness of an act proscribed by criminal law is in fact an element of the crime, and as such, the prosecution bears the burden of proving such fact.

The prosecution does not need to show, however, that every act was voluntary in order to establish culpability.It is sufficient that the defendant’s conduct – which is the actual and proximate cause of the social harm – included a voluntary act.

Voluntary Act
Model Penal Code – Similar to the common law, MPC § 2.01 requires that criminal conduct include a voluntary act. It does not define the term “voluntary,” but Comments list bodily movements that are involuntary: reflexes, convulsions, conduct during unconsciousness, sleep, or due to hypnosis, as well as any conduct that “is not a product of the effort or determination of the defendant, either conscious or habitual.” Excluded from the requirement that the act be voluntary are offenses that constitute a “violation” [§2.05], defined as an offense for which the maximum penalty is a fine or civil penalty.