(a) Sufficiency. A determination of deportability shall not be valid unless it is found by clear, unequivocal, and convincing evidence that the facts alleged as grounds for deportation are true.

(b) Use of prior statements. The immigration judge may receive in evidence any oral or written statement that is material and relevant to any issue in the case previously made by the respondent or any other person during any investigation, examination, hearing, or trial.

(c) Testimony. Testimony of witnesses appearing at the hearing shall be under oath or affirmation administered by the immigration judge.

(d) Depositions. The immigration judge may order the taking of depositions pursuant to § 1003.35 of this chapter.