17 CFR § 12.208 - Submissions of proof.
(a) Documentary evidence. Each party may file and serve verified statements of fact and affidavits of non-party witnesses with personal knowledge of the facts which they aver to be true. Proof in support of the complaint and in support of the respondent's answer may be found in those verified documents, in affidavits of non-party witnesses, in other verified statements of fact, and in other documents and tangible exhibits.
(b) Oral testimony and examination. The Judgment Officer may order an oral hearing for the presentation of testimony and examination of the parties and their witnesses when appropriate and necessary for the resolution of factual issues, upon motion by either a party or the Judgment Officer. An oral hearing held under this section will be convened by conference telephone call as provided in § 12.209(b), except that an in-person hearing may be held in Washington, DC, under the circumstances set forth in § 12.209(c).