Patterson v. New York
United States Supreme Court
432 U.S. 197 (1977)
Patterson (defendant) shot and killed his estranged wife's new boyfriend and was charged with second-degree murder; he raised New York's affirmative defense of extreme emotional disturbance, which could mitigate the charge to manslaughter, but the jury was instructed he bore the burden of proving that defense by a preponderance of the evidence. The jury convicted him of second-degree murder, and the New York Court of Appeals affirmed, rejecting his argument that the state should instead bear the burden of disproving the defense.
Whether the state is required to prove every element of a crime beyond a reasonable doubt, and whether a defendant may nonetheless be required to prove an affirmative defense.