The burden of proof at the certification and recertification hearings under this chapter shall be on the petitioner to show, by clear and convincing evidence, that:
(1) The child is mentally ill or has symptoms of mental illness;
(2) The child is dangerous to himself or others;
(3) The child can benefit from treatment available only at a hospital; and (4) No less restrictive alternative is available which will be effective in treating the child.