What is the standard of evidence required to sustain a finding of premeditation and deliberation in a murder trial?

The court refused to give an instruction, based on People v. Anderson (1968) 70 Cal.2d 15, 26-27, 73 Cal.Rptr. 550, 447 P.2d 942, which would have told the jurors that "[t]he type of evidence which the courts have found proper to sustain a finding of premeditation and deliberation falls into three basic categories:" (1) evidence of planning activity, (2) evidence of motive, and (3) inferences based on the nature of the killing. "A finding of premeditation and deliberation may occur where there is evidence of all ... types ... and otherwise requires at least strong evidence of type one or evidence of [type] two in conjunction with either type one or three." ²³