a) Excluding extraordinary circumstances, the Department may retain temporary custody of an Indian child for a reasonable period of time not to exceed 90 days. Continued custody after that period may occur only upon a court finding supported by clear and convincing evidence. This standard is appreciably higher than that ordinarily required for findings of neglect, dependency or for a minor in need of supervision. Under the Indian Child Welfare Act, the involuntary placement hearing also requires the testimony of expert witnesses who can assert that the child is likely to suffer serious emotional or physical injury if returned to the custody of the parent or Indian custodian. The court must decide that the child is in danger if left with the parents.