Commonwealth v. York

Commonwealth v. York, 50 Mass. (9 Metcalf) 93 (1845), is a precedent setting American criminal case in which it was determined that although the prosecution must establish all of the elements of a crime beyond a reasonable doubt, the defendant must prove the defense of provocation, which is about the defendant's mental state.[1]^:17 This was consistent with Blackstone's Commentaries that the prosecution must prove the defendant committed a criminal act, and the defendant must then prove "circumstances of justification, excuse and alleviation".[1]^:17[2] In federal courts, but not state all courts, this changed with Davis v. United States (1895), which set precedent that there is a presumption of innocence as to having a mental state of being "legally capable of committing crime".[1]^:17