What is the test for reducing first degree murder to second degree murder?

Noting that provocation insufficient to reduce murder to voluntary manslaughter might, nonetheless, create a doubt as to deliberation and premeditation and thus reduce first degree murder to second degree murder, and finding evidence of such provocation, the court reversed on the basis the trial court had erred in failing to instruct on the lesser included offense of second degree murder. (People v. Wickersham, supra, 32 Cal.3d at pp. 329-330, 185 Cal.Rptr. 436, 650 P.2d 311.)