A 42-year-old woman undergoes elective laparoscopic cholecystectomy for symptomatic cholelithiasis. The surgeon performs the procedure without obtaining informed consent, claiming the patient was anxious and time was limited. Postoperatively, the patient develops a bile duct injury requiring open exploration and hepaticojejunostomy. The patient sues for negligence. Which of the following best describes the legal principle that applies to the surgeon's failure to obtain informed consent?