Is a failure to give a nonstatutory manslaughter instruction prejudicial per se?

Appellant then cites People v. Griffin (1971) 18 Cal.App.3d 864, 96 Cal.Rptr. 218, for the proposition that failure to give a nonstatutory manslaughter instruction, Sua sponte, is prejudicial per se where the defense of diminished capacity is properly before the court and the court has been alerted to it by the evidence presented. That proposition is true where the case is tried on some theory of murder other than felony murder. In Griffin, careful reading of the opinion itself ⁵ shows the case [98 Cal.App.3d 719] was tried on murder grounds in addition to felony murder. (Id., at pp. 868, fn. 1, 870, 96 Cal.Rptr. 218.)