Informed consent is a legal condition whereby a person can be said to have given consent based upon an appreciation and understanding of the facts and implications of any actions. The individual needs to be in possession of all of his faculties, such as not mentally retarded or mentally ill, without an impairment of judgment at the time of consenting. Impairments include sleep, illness, intoxication, drunkenness, using drugs or other health problems. Some acts cannot legally take place because of a lack of informed consent. In other cases, consent of someone on behalf of a person, not considered able to have informed consent, is valid. Examples of this include the parents or legal guardians of a child and caregivers for the mentally ill.