How have the courts interpreted "other crimes" in the penalty phase?

Prior cases explain that the facts tending to prove the defendant's other crimes for purposes of establishing his criminal knowledge or intent are deemed mere "evidentiary facts" that need not be proved beyond a reasonable doubt as long as the jury is convinced, beyond such doubt, of the truth of the "ultimate fact" of the defendant's knowledge or intent. (People v. Lisenba, supra, 14 Cal.2d at pp. 430-431, 94 P.2d 569 and cases cited.)

The courts have acknowledged that "other crimes" evidence may have a substantial impact on the jury's determination whether the defendant should [11 Cal.4th 764] live or die. (People v. Robertson, supra, 33 Cal.3d at pp. 53-54, 188 Cal.Rptr. 77, 655 P.2d 279.) Thus, at the penalty phase, it is appropriate to require proof beyond a reasonable doubt as to defendant's other crimes, given the high potential for prejudice. To require such exacting proof at the guilt phase, however, could convert the guilt phase into a series of collateral mini-trials conducted whenever the People seek to rely on such evidence to assist in proving defendant's identity, intent or similar [906 P.2d 43] element of the charged offense. The risk of "sidetracking" the trial would be enormous.