In Canterbury v. Spence, 464 F 2d 772, 150 U.S. App. D.C. 263 (D.C Cir - 1972), the Court held that the duty and required scope of disclosure standards in the medical profession must be established by expert medical testimony but "tested by general considerations of reasonable disclosure under all the circumstances will materially affect the patient's decision to proceed with the treatment. This is not a retrospective determination. There should be no criticism of the physician unless the fact-finder determines that the information was inadequate." (Canterbury v. Spence, 464 F 2d supra at 787.) Consideration of the patient's veracity shifts the focus from the time relevant to causation; the time juncture at which her (or his) consent was given. Waltz & Schneurman supra at 646. The proper rule is to resolve the causality issue on an objective basis; i.e. what a reasonably prudent person in the patient's circumstances would have decided if reasonably informed of the significant perils. The patient's testimony is relevant, but not determinative. (Canterbury v. Spence, 464 F 2d supra at 790.) The United States Court of Appeals for the District of Columbia Circuit opined that: "lay witness testimony can competently establish a physician's failure to disclose particular risk information, the patient's lack of knowledge of the risk, and the adverse consequences following the treatment."