What is the state of the mental state of a defendant in a first degree murder case?

It was incumbent on the trial judge in the present case to fully define for the jury the particular mental states required for the crimes of first degree murder, second degree murder and voluntary manslaughter. Thus, the court erred in refusing to give the requested instruction that [46 Cal.App.3d 301] malice aforethought, either express or implied, is manifested by the doing of an act by a person who is able to comprehend his obligation to act within the law. (People v. Conley, Supra, 64 Cal.2d at p. 324, fn. 4, 49 Cal.Rptr. 815, 411 P.2d 911.)