How have medical records been used to determine if a plaintiff has been sexually assaulted?

The defendant in People v. Huyhn (2012) 212 Cal.App.4th 285 (Huynh) was charged with drugging and murdering one man, and with drugging and sexually assaulting another. The surviving victim had no memory of what occurred and was taken to a medical facility, where a sexual assault exam was performed. The nurse who conducted that exam observed and photographed various signs that the victim had been sodomized and otherwise sexually assaulted. That nurse was unavailable to testify at defendant's trial, so her supervisor testified about the examination results in her stead, opining based on the photographs that the victim's anus showed signs of significant trauma.