(1) In arriving at its adjudicatory decision, the youth court shall consider only evidence which has been formally admitted at the adjudicatory hearing. All testimony shall be under oath and may be in narrative form. In proceedings to determine whether a child is a delinquent child or a child in need of supervision, the youth court shall admit any evidence that would be admissible in a criminal proceeding. In proceedings to determine whether a child is a neglected child or an abused child, the youth court shall admit any evidence that would be admissible in a civil proceeding.

(2) An out-of-court admission by the child, even if otherwise admissible, shall be insufficient to support an adjudication that the child is a delinquent child unless the admission is corroborated, in whole or in part, by other competent evidence.

(3) Members of the youth court staff may appear as witnesses except that no member of the youth court staff may testify as to an admission or confession made to him.

(4)

(a) No statements, admissions or confessions made by or incriminatory information obtained from a child in the course of a screening or assessment that is undertaken in conjunction with any proceedings under this chapter, including, but not limited to, that which is court-ordered, shall be admitted into evidence against the child on the issue of whether the child committed a delinquent act under this chapter or on the issue of guilt in any criminal proceedings.

(b) The provisions of paragraph (a) of this subsection are in addition to and do not override any existing statutory and constitutional prohibition on the admission into evidence in delinquency and criminal proceedings of information obtained during screening, assessment or treatment.