Mullaney v. Wilbur, 421 U.S. 684 (1975) (U.S. Supreme Court)
Mullaney v. Wilbur is a landmark Supreme Court decision at the intersection of criminal law and constitutional due process.
Does the Due Process Clause of the Fourteenth Amendment permit a state, in a murder prosecution, to require the defendant to prove by a preponderance of the evidence that he acted in the heat of passion on sudden provocation in order to reduce the crime to manslaughter?
Under the Due Process Clause, the prosecution must prove beyond a reasonable doubt every fact necessary to constitute the crime charged. When a state's definition of murder requires proof of malice aforethought and treats the absence of heat of passion (or the presence of malice) as critical to distinguishing murder from manslaughter, the State may not shift to the defendant the burden of proving heat of passion; rather, once that issue is properly presented, the State must prove the absence of heat of passion beyond a reasonable doubt.
No. Maine's burden-shifting scheme violated due process. When the issue is properly presented, the State must prove beyond a reasonable doubt the absence of heat of passion on sudden provocation to establish murder. The judgment granting habeas relief to Wilbur was affirmed.
Mullaney v. Wilbur is a cornerstone of the constitutional law of criminal burdens of proof. It reinforces Winship's principle by preventing states from evading the beyond-a-reasonable-doubt requirement through relabeling elemental facts as mitigating circumstances. For homicide, it means that when a defendant introduces evidence of heat of passion, the prosecution must prove its absence to secure a murder conviction. The case significantly influenced jury instruction practices and prosecutorial burdens nationwide. Later, Patterson v. New York narrowed Mullaney's reach by permitting states to place the burden of persuasion on defendants for true affirmative defenses that do not negate an element of the offense (e.g., extreme emotional disturbance in New York's statutory scheme). Still, Mullaney remains vital for understanding the distinction between elements and affirmative defenses, for structuring homicide prosecutions and defenses, and as an early antecedent to the Apprendi line of cases emphasizing the jury's role and the State's burden for facts that increase culpability or punishment.