What is the legal test for the admissibility of expert testimony in a personal injury case?

The general test for the admissibility of expert testimony is whether the jury can derive 'appreciable help' from such testimony. That determination, which necessitates balancing the probative value of the tendered testimony against its potential prejudicial effect, is committed to the broad discretion of the district court; it will not be disturbed on appeal unless manifestly erroneous. See United States v. Amaral, 488 F.2d 1148, 1152 (9th Cir. 1973).