Model Penal Code § 2.01
§ 2.01. Requirement of Voluntary Act; Omission as Basis of Liability; Possession as an Act.
(1) A person is not guilty of an offense unless his liability is based on conduct that includes a voluntary act or the omission to perform an act of which he is physically capable.
(2) The following are not voluntary acts within the meaning of this Section:
(a) a reflex or convulsion;
(b) a bodily movement during unconsciousness or sleep;
(c) conduct during hypnosis or resulting from hypnotic suggestion;
(d) a bodily movement that otherwise is not a product of the effort or determination of the actor, either conscious or habitual.
(3) Liability for the commission of an offense may not be based on an omission unaccompanied by action unless:
(a) the omission is expressly made sufficient by the law defining the offense; or
(b) a duty to perform the omitted act is otherwise imposed by law.
(4) Possession is an act, within the meaning of this Section, if the possessor knowingly procured or received the thing possessed or was aware of his control thereof for a sufficient period to have been able to terminate his possession.
5. Distinguish two cases: Defendant’s arm moves as a result of a spasm and the arm hits another person; defendant is unaware that another person is behind him when he raises his arm to swat a fly and without intending to, he hits the other person.