What is the test for evidence of voluntary intoxication in a murder case?

Prior to 1995, section 22, subdivision (b), provided in part, "Evidence of voluntary intoxication is admissible on the issue of whether or not the defendant actually formed a required specific intent, or, when charged with murder, whether the defendant premeditated, deliberated, or harbored malice aforethought." (Stats. 1982, ch. 893, 2.) Thus, prior to 1995, evidence of voluntary intoxication was admissible with regard to whether the defendant harbored malice aforethought, either express or implied. (People v. Whitfield (1994) 7 Cal.4th 437, 448-451.)