When will a jury reduce murder to manslaughter by negating malice?

Although duress cannot reduce murder to manslaughter by negating malice (People v. Anderson, supra, 28 Cal.4th at pp. 770, 781-784, 122 Cal. Rptr.2d 587, 50 P.3d 368), the court nevertheless gave instructions that authorized the jury to consider the effect of threats on the mental states requisite to murder and manslaughter. The jury was told that to establish that a killing is murder, the prosecution had the burden of proving beyond a reasonable doubt that the "act which caused the death was not done ... in a killing punishable by death, in the honest belief in the necessity to protect oneself against imminent peril to life or great bodily injury, whether or not that belief was reasonable or unreasonable." It was further told that "there is no malice aforethought in a killing punishable by death if the killing occurred in the honest belief in the necessity to protect oneself against imminent peril to life or great bodily injury, whether or not that belief was reasonable or unreasonable" and that, in such instance, the offense is voluntary or involuntary manslaughter. Again, because the instructions were unduly favorable to defendant, he cannot complain.