What is the legal test for an expert testimony in a medical malpractice case?

Under California law, a person with "special knowledge, skill, experience, training, or education" in a particular field may qualify as an expert witness (Evid. Code, 720), and give testimony in the form of an opinion (Evid. Code, 801). A trial court generally has "broad discretion in deciding whether to admit or exclude expert testimony [citation], and its decision as to whether expert testimony meets the standard for admissibility is subject to review for abuse of discretion." (People v. McDowell (2012) 54 Cal.4th 395, 426.)

Expert opinion testimony is admissible only if the subject matter of that testimony is "sufficiently beyond common experience that the opinion of an expert would assist the trier of fact." (Evid. Code, 801, subd. (a).) " 'Generally, an expert may render opinion testimony on the basis of facts given "in a hypothetical question that asks the expert to assume their truth." [Citation.]' " (People v. Vang (2011) 52 Cal.4th 1038, 1045 (Vang).) " 'Such a hypothetical question must be rooted in facts shown by the evidence. ...' " (Ibid.)