(a) Except as provided in paragraph (b) of this section, testimony at the hearing shall be given orally by witnesses under oath or affirmation.

(b) At the discretion of the ALJ, testimony may be admitted in the form of a written statement or deposition. In order to be admissible, any written statement must be provided to all other parties along with the last known address of the witness, in a manner that allows sufficient time for other parties to subpoena the witness for cross-examination at the hearing.