431.061.  Consent to surgical or medical treatment, who may give, when. — 1.  In addition to such other persons as may be so authorized and empowered, any one of the following persons if otherwise competent to contract, is authorized and empowered to consent, either orally or otherwise, to any surgical, medical, or other treatment or procedures, including immunizations, not prohibited by law:

  (1)  Any adult eighteen years of age or older for himself;

  (2)  Any parent for his minor child in his legal custody;

  (3)  Any minor who has been lawfully married and any minor parent or legal custodian of a child for himself, his child and any child in his legal custody;

  (4)  Any minor for himself in case of:

  (a)  Pregnancy, but excluding abortions;

  (b)  Venereal disease;

  (c)  Drug or substance abuse including those referred to in chapter 195;

  (5)  Any adult standing in loco parentis, whether serving formally or not, for his minor charge in case of emergency as defined in section 431.063;

  (6)  Any guardian of the person for his ward;

  (7)  Any relative caregiver of a minor child as provided for under section 431.058.

  2.  The provisions of sections 431.061 and 431.063 shall be liberally construed, and all relationships set forth in subsection 1 of this section shall include the adoptive and step-relationship as well as the natural relationship and the relationship by the half blood as well as by the whole blood.

  3.  A consent by one person so authorized and empowered shall be sufficient notwithstanding that there are other persons so authorized and empowered or that such other persons shall refuse or decline to consent or shall protest against the proposed surgical, medical or other treatment or procedures.

  4.  Any person acting in good faith and not having been put on notice to the contrary shall be justified in relying on the representations of any person purporting to give such consent, including, but not limited to, his identity, his age, his marital status, and his relationship to any other person for whom the consent is purportedly given.