What is the test for admitting to a criminal offence?

Section 1101, subdivision (a) limits the admissibility of evidence of a person's past conduct "when offered to prove his or her conduct on a specified occasion." It "generally prohibits the admission of a prior criminal act against a criminal defendant" for the purpose of showing that he or she acted similarly on the occasion in question. (People v. Cole (2004) 33 Cal.4th 1158, 1194.) However, subdivision (b) of the statute provides that evidence of a defendant's prior criminal acts is admissible "when relevant to prove some fact (such as motive, opportunity, intent, preparation, plan, knowledge, identity, absence of mistake or accident . . .) other than his or her disposition to commit such an act." ( 1101, subd. (b).)