Is an expert's opinion not relevant to her defense in a personal injury case?

Salzer nevertheless argues that her expert's opinion was relevant to her defense and would have assisted the jury to understand her defense. The district court, however, repeatedly ruled that the proffered evidence would not aid the jury. A court is entitled to exclude even relevant expert testimony when the court concludes that such testimony will not assist the trier of fact in drawing its own conclusion as to a fact in issue. See United States v. Rahm, 993 F.2d 1405, 1411 (9th Cir.1993).