The tort of trespass protects a person from being touched without his consent. The ethical principal of autonomy underlies the law of consent which authorizes the patient to decide what should be done to his body. An act of trespass may also amount to a criminal offence. Where the patient has not been given enough information before treatment, the tort of negligence may be applicable. The general rule of medical treatment is that consent of every patient must be obtained before treatment, failing which the patient is entitled to a right of action in trespass. The patient must possess the capacity to give a legally valid consent and moreover, the patient must be able to understand the nature and purpose of the treatment to consent to it. Some guidelines have been laid down by the Court of Appeal for dealing with patients who lack capacity to give consent. A patient is considered to be without capacity to give consent if he or she is unable due to mental disability to make a decision on the matter in question or unable to communicate a decision on that matter because of unconsciousness or for any other reason. The tort of trespass to the person comprises assault, battery and false imprisonment. The medical staff may be charged with criminal offences arising out of their work. At common law, criminal assault refers to threat of violence and the offence of battery involves some physical contact. A number of offences have been provided under the Offences Against the Person Act, 1861. The medical staff may face prosecution where a patient is given treatment without his consent or is given treatment in spite of refusing to give consent.