All of the following are defence against professional negligence except

Vicarious liability: Responsibility lies on the superior for the negligent action of his subordinate who is supposed to work under the guidance of the superior. The principle applied is called " respondent superior " which means 'let the master answer'. To apply this principle, the following conditions are to be satisfied: 1. There must be an employer employee relationship to be established. 2. The employee's conduct should occur within the scope of his employment. 3. The negligence occurred while on the job. Generally the main doctor becomes responsible for the negligence of his assistant. That does not mean that the junior is not responsible. He is also responsible if that duty is entrusted on him. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr. PC IGNATIUS PAGE NO 381