What is the test for admitting testimony regarding battered woman syndrome in a criminal case?

In criminal actions in California, the prosecution or defense may admit expert testimony regarding battered woman syndrome and its effects, "including the nature and effect of physical, emotional, or mental abuse on the beliefs, perceptions, or behavior of victims of domestic violence," so long as the expert's testimony is relevant and the expert is qualified. Cal. Evid. Code 1107. Battered woman syndrome evidence is relevant when there is sufficient evidence that the syndrome applies to the defendant, and battered woman syndrome testimony is probative of a contested issue. People v. Gadlin, 78 Cal. App. 4th 587, 592 (2000) (citations omitted).