How has the statute of limitations in sexual assault cases been interpreted?

Doe 4's allegation was that defendant committed a lewd act on her when she was 15, and as noted, her age at the time of the act is what defendant here claims was not corroborated at trial. "When an issue involving the statute of limitations has been tried, we review the record to determine whether substantial evidence supports the findings of the trier of fact." (People v. Castillo (2008) 168 Cal.App.4th 364, 369.) Doe 4 testified that in the spring of 1994 when she was 15 years old, she and defendant had sex for the first time at a hotel in Humboldt County. The independent evidence corroborating Doe 4's age as 15 came from defendant and Doe 1. Defendant testified that he and L.S.'s oldest son was born in 1994, sometime after August 14. Their daughter, Doe 1, testified she was born in 1998. Defendant testified that Doe 1 came to live with them when she was eight days old. Defendant testified that there was some truth to what Doe 4 testified, namely, that he was in the hotel room with Doe 4 and "Louis," but he told Doe 4 he was married, they did not have sex, and it was during 1998 or 1999. On cross-examination, he noted that at the time he met Doe 4, his wife was at home taking care of "Boo-Boo," which was the nickname of their older son. Had this encounter in the motel taken place in 1998 or 1999, as defendant testified, L.S. would have been at home taking care of two young children, not just one. Thus, independent evidence corroborated Doe 4's testimony that she was 15 when defendant committed the lewd act.