What is the test for admissibility of expert testimony in a medical malpractice case?

If a witness has disclosed sufficient knowledge of the subject to allow the witness's opinion to go to the jury, "the question of the degree of his knowledge goes to the weight of his testimony rather than to its admissibility." (Brown v. Colm, supra, 11 Cal.3d at p. 643.)

An expert may render opinion testimony on the basis of facts given in a hypothetical question that asks the expert to assume their truth. But such a hypothetical question must be rooted in facts shown by the evidence. (People v. Gardeley (1996) 14 Cal.4th 605, 618.)

Our task in reviewing a trial court's order for abuse of discretion has been described as follows:

"`Discretion is abused whenever, in its exercise, the court exceeds the bounds of reason, all of the circumstances before it being considered. The burden is on the party complaining to establish an abuse of discretion, and unless a clear case of abuse is shown and unless there has been a miscarriage of justice a reviewing court will not substitute its opinion and thereby divest the trial court of its discretionary power.'" (Denham v. Superior Court (1970) 2 Cal.3d 557, 566.)