In relevant part, CALJIC No. 8.50 reads: "The distinction between murder . . . and manslaughter is that murder . . . requires malice while manslaughter does not. When the act causing the death, though unlawful, is done in the heat of passion or is excited by a sudden quarrel that amounts to adequate provocation, or in the actual but unreasonable belief in the necessity to defend against imminent peril to life or great bodily injury, the offense is manslaughter. In that case, even if an intent to kill exists, the law is that malice, which is an essential element of murder, is absent. to establish that a killing is murder . . . and not manslaughter, the burden is on the People to prove beyond a reasonable doubt each of the elements of murder and that the act which caused the death was not done in the heat of passion or upon a sudden quarrel or in the actual, even though unreasonable, belief in the necessity to defend against imminent peril to life or great bodily injury." In Mullaney v. Wilbur (1975) 421 U.S. 684, 704, the Supreme Court held that, when the issue is properly presented in a murder case, the due process clause of the United States Constitution requires the prosecution to prove the absence of heat of passion. (See also People v. Najera (2006) 138 Cal.App.4th 212, 227 (Najera); People v. Rios (2000) 23 Cal.4th 450, 462.) CALJIC No. 8.50 so provides. "In such cases, if the fact finder determines the killing was intentional and unlawful, but is not persuaded beyond reasonable doubt that provocation (or imperfect self-defense) was absent, it should acquit the defendant of murder and convict him of voluntary manslaughter." (People v. Rios, at p. 462.)