What is the preponderance of evidence standard in sexual assault cases?

permitted the jury to find by a preponderance of evidence that appellant committed the prior crimes, to infer from such commission of the prior crimes that appellant had a disposition to commit such crimes, and to infer from such disposition that appellant 'did commit' the charged crimes, without necessarily being convinced beyond a reasonable doubt that appellant committed the charged crimes. If the jury followed these instructions literally and arrived at a guilty verdict in that manner, appellant was denied his due process right to require proof beyond a reasonable doubt of every fact necessary to constitute the charged crimes. [Citations.] A 'constitutional infirmity arises' because taken literally these instructions authorized a conviction of the current charges based 'solely' upon a finding that appellant committed the prior crimes. (People v. Vichroy, supra, 76 Cal.App.4th at pp. 99, 101.) In Vichroy the trial court did not instruct the jury about the preponderance of evidence standard for proof of the prior crimes. The appellate court found error because, even assuming the prior crimes were proved beyond a reasonable doubt, '[w]e do not believe proof beyond a reasonable doubt of a basic fact, that appellant committed prior sexual offenses, may act as "proxy" or substitute for proof of the ultimate fact, i.e., appellant's guilt of the currently charged offenses.' (Id. at p. 99.) The 'constitutional infirmity' is even greater where, as here, the jury was also instructed that the prior crimes need only be proved by a preponderance of evidence." (People v. Orellano, supra, at pp. 184185.)