What is the test on substantial evidence in a medical malpractice case?

Our remaining instant inquiry is whether the above findings of fact were supported by substantial evidence. The test on appeal in such cases is whether substantial evidence supports the conclusion of the trier of fact, not whether the evidence proves essential facts beyond a reasonable doubt, or by clear and convincing evidence. The appellate court must determine whether a reasonable trier of fact, on the whole evidence, could have found such a degree of proof. (See People v. Johnson, 26 Cal.3d 557, 576, 162 Cal.Rptr. 431, 606 P.2d 738.)