good faith for Z's benefit, performs that operation on Z. with Z's consent. A has-committed no offence. 89. Act done In good faith for benefit of child or insane person, by or by consent of guardian: Nothing which is done in good faith for the benefit of a person under twelve years of age, or of unsound mind, by or by consent, either express or implied, of the guardian or other person having lawful charge of that person, is an offence by reason of any harm which it may cause, or be intended by the doer to cause or be known by the doer to be likely to cause to that person: Provided First: That this exception shall not extend to the intentional causing of death, or to the attempting to cause death; Secondly: That this exception shall not extend to the doing of anything which the person doing it knows to be likely to cause death, for any purpose other than the preventing of death or grievous hurt; or the curing of any grievous disease or infirmity; Thirdly: That this exception shall not extend to the voluntary causing of grievous hurt, or to the attempting to cause grievous hurt, unless it be for the purpose of preventing death or grievous hurt, or the curing of any grievous disease or infirmity; Fourthly: That this exception shall not extend to the abetment of any offence, to the committing of which offence it would not extend. Illustration A, in good faith, for his child's benefit without his child's consent, has his child cut for the stone by "a surgeon, knowing it to be likely that the operation will cause the child's death, but not intending to cause the child's death. A is within the exception, inasmuch as his object was the cure of the child. 90. Consent known to be given under fear or misconception: A consent is not such a consent as is intended by any action of this Code, if the consent is given by a person under fear of injury, or under a misconception of fact, and if the person doing the act knows, or has reason to believe, that the consent was given in consequence of such fear or misconception; or Consent of insane person: If the consent is given by a person who, from unsoundness of mind, or intoxication, is unable to understand the nature and consequence of that to which he gives his consent; or Consent of child: Unless the contrary appears from the context, if the consent is given by a person who is under twelve years of age. 91. Exclusion of acts which are offences independently of harm caused : The exceptions in Sections 87, 88 and 89 do not extend to acts which are offences