What is the test for excluding expert testimony from a trial?

We review a trial court's decision to exclude expert testimony for an abuse of discretion. (People v. Pearson (2013) 56 Cal.4th 393, 443.) Expert testimony must be "[r]elated to a subject that is sufficiently beyond common experience" such that it will assist the trier of fact. (Evid. Code, 801, subd. (a).) And, like any evidence, it must be relevant and have adequate foundation. (Evid. Code, 210.)

Thus, where expert testimony is offered in support of a theory of self-defense, there must be independent evidence supporting the requisites of the defense. (See People v. Brown (2004) 33 Cal.4th 892, 908 [there must "be independent evidence of domestic violenceotherwise the expert testimony about how victims of domestic violence behave would lack foundation"]; People v. Romero (1999) 69 Cal.App.4th 846, 856 (Romero)

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