The court may approve a request for the withholding or withdrawal of a life-sustaining procedure from a disabled person on the basis of a substituted judgment. The court may make a substituted judgment under subsection (a) of this section only on the basis of clear and convincing evidence that the disabled person would, if competent, decide to withhold or withdraw a life-sustaining procedure under the circumstances. Evidence of the intentions or wishes of the disabled person regarding the withholding or withdrawal of a life-sustaining procedure that might otherwise be inadmissible may be admitted, in the discretion of the court, if it is: Material and probative; and The best evidence available.