It is not essential to the validity of any consent for the furnishing of health care services that the consent be in writing or any other specific form of expression; provided however, when the giving of such consent is recited or documented in writing and expressly authorizes the health care services to be furnished, and when such writing or form has been executed or initialed by a person competent to give such consent for himself or another, such written consent, in the absence of convincing proof that it was secured maliciously or by fraud, is presumed to be valid for the furnishing of such health care services, and the advice and disclosures of the attending licensed independent practitioner or dentist, as well as the level of informed awareness of the giver of such consent, shall be presumed to be sufficient.