What is the test for determining whether a defendant committed a specific crime?

"The other consideration is predicated upon fundamental notions of due process.... 'Emerging from recent cases dealing with the problems arising when a crime is charged and the evidence describes several acts, any one of which could constitute the crime charged, "is the so-called 'either/or' rule: ... either the prosecution must select the specific act relied upon to prove the charge or the jury must be instructed in the words of CALJIC No. 17.01 ... or [the] equivalent that it must unanimously agree beyond a reasonable doubt that defendant committed the same specific criminal act. [Citations.]" [Citation.]' (People v. Callan (1985) 174 Cal.App.3d 1101, 1111 [220 Cal.Rptr. 339] fn. omitted....)