serious emotional distress

On December 27, 1970, Gordon Patterson shot and killed John Northrup in Glens Falls, New York. After a brief and unstable marriage, Patterson had become estranged from his wife Roberta. Roberta had resumed an association with Northrup, a neighbor to whom she had been engaged before her marriage to Patterson. Patterson borrowed a rifle from an acquaintance and went to the residence of his father-in-law. There he observed his wife through a window in a state of semiundress in Northrup's presence. He entered the house and killed Northrup by shooting him twice in the head. Patterson was charged with second-degree murder. At his jury trial in Warren County Court, Patterson raised the affirmative defense of extreme emotional disturbance and presented psychiatric evidence tending to show that he had been extremely emotionally disturbed when he killed Northrup. The jury was instructed that the prosecution had the burden of proving beyond a reasonable doubt each element of the crime of murder. The defendant had the burden of proving the affirmative defense by a preponderance of the evidence. The jury convicted Patterson of second-degree murder. The Appellate Division affirmed the conviction. While appeal to the New York Court of Appeals was pending, this Court decided Mullaney v. Wilbur. The New York Court of Appeals nevertheless affirmed, distinguishing the Maine statute at issue in Mullaney and holding that New York's allocation of the burden of proof on the affirmative defense was consistent with due process. The United States Supreme Court granted certiorari limited to the question whether the burden of proof placed on the defendant by New York law is consistent with the Due Process Clause of the Fourteenth Amendment.