What is the impact of expert evidence on the standard of care of a doctor who fails to disclose the risks to a patient?

I also refer to the judgment in Reibl, supra, at pp. 13-4: Generally, the failure to mention statistics should not affect the duty to inform nor be a factor in deciding whether the duty has been breached. To allow expert medical evidence to determine what risks are material and, hence, should be disclosed and, correlatively, what risks are not material is to hand over to the medical profession the entire question of the scope of the duty of disclosure, including the question whether there has been a breach of that duty. Expert medical evidence is, of course, relevant to findings as to the risks that reside in or are a result of recommended surgery or other treatment. It will also have a bearing on their materiality but this is not a question that is to be concluded on the basis of the expert medical evidence alone. The issue under consideration is a different issue from that involved where the question is whether the doctor carried out his professional activities by applicable professional standards. What is under consideration here is the patient's right to know what risks are involved in undergoing or foregoing certain surgery or other treatment. The materiality of non-disclosure of certain risks to an informed decision is a matter for the trier of fact, a matter on which there would, in all likelihood, be medical evidence but also other evidence, including evidence from the patient or from members of his family. It is, of course, possible that a particular patient may waive aside any question of risks and be quite prepared to submit to the surgery or treatment, whatever they may be. Such a situation presents no difficulty. Again, it may be the case that a particular patient may, because of emotional factors, be unable to cope with facts relevant to recommended surgery or treatment and the doctor may, in such a case, be justified in withholding or generalizing information as to which he would otherwise be required to be more specific. A useful summary of issues on which medical evidence in non-disclosure cases remains significant is found in a "Comment, New Trends in Informed Consent", 54 Neb. L. Rev. 66 (1975), at p. 90, where, after noting that medical evidence should not control determination of the breach of the standard of care, it continued, as follows (referring to Canterbury v. Spence, infra [Canterbury v. Spence et al. (1972), 464 F. 2d 772; cert, denied 409 U.S. 1064n]): "Even Canterbury specifically notes that expert testimony will still be required, in all but the clearest instances, to establish (1) risks inherent in a given procedure or treatment, (2) the consequences of leaving the ailment untreated, (3) alternative means of treatment and their risks, and (4) the cause of the injury suffered by the plaintiff-patient. Finally, if the defendant-physician claims a privilege, expert testimony is needed to show the existence of (1) an emergency which would eliminate the need for obtaining consent, and (2) the impact upon the patient of risk disclosure where a full disclosure appears medically unwarranted."