A 35-year-old woman underwent laparoscopic cholecystectomy. Postoperatively, she developed bile peritonitis due to an unrecognized bile duct injury. She was not informed preoperatively about the risk of bile duct injury (incidence ~0.3–0.7%), though it is a known complication of the procedure. The patient claims lack of informed consent. Which investigation is most appropriate to establish whether the surgeon breached the duty to disclose risks?