Gordon Patterson, Jr. (defendant) had a brief and unstable marriage with his wife, Roberta. After they separated, Roberta began seeing an old boyfriend. Patterson borrowed a rifle from an acquaintance and shot the boyfriend, killing him. Patterson was charged with second-degree murder. At trial, Patterson raised the state-recognized affirmative defense that he had acted under extreme emotional disturbance. The jury was instructed that Patterson had the burden of proving his affirmative defense by a preponderance of the evidence. If Patterson proved the affirmative defense, it would have mitigated the second-degree murder charge to manslaughter. The jury found Patterson guilty of second-degree murder and he appealed. The Court of Appeals of New York affirmed the conviction and rejected Patterson’s argument that the burden of proving extreme emotional disturbance fell on the state, not on Patterson. Patterson appealed.