(a) Capacity to amend.--While having the capacity to make mental health decisions, a declarant may amend a declaration by a writing executed in accordance with the provisions of section 5822 (relating to execution).
(b) Determination of capacity.--During the period of involuntary treatment pursuant to Article III of the act of July 9, 1976 (P.L.817, No.143), known as the Mental Health Procedures Act, a declarant may amend the declaration if the individual is found to be capable of making mental health decisions after examination by a psychiatrist and one of the following: another psychiatrist, a psychologist, family physician, attending physician or mental health treatment professional. Whenever possible, at least one of the decision makers shall be a treating professional of the declarant or principal.