What is the test for "imperfect self defense" to negate malice in a murder case?

Self-defense requires an actual and reasonable belief in the need to defend against an imminent danger of death or great bodily injury. (People v. Humphrey (1996) 13 Cal.4th 1073, 1082, 56 Cal. Rptr.2d 142, 921 P.2d 1.) If, however, the killer actually, but unreasonably, believed in the need to defend him or herself from imminent death or great bodily injury, the theory of "imperfect self defense" applies to negate malice. (Ibid.) The crime committed is thus manslaughter, not murder. (Ibid.)

[93 Cal.App.4th 1262]