The admission of Battered Women’s Syndrome (BWS) testimony by an expert pursuant to California Evidence Code section 1107 in a spousal abuse prosecution did not render the trial so fundamentally unfair as to violate due process. The expert testimony about BWS tended to discredit the victim’s changed story about who inflicted her injuries, but her credibility was destroyed anyway by the testimony of responding police officers. The evidence against Dillard was overwhelming, and even if the admission of the testimony was error under California law, it did not violate Dillard’s due process rights.