50 CFR § 228.18 - Cross-examination.
(a) The presiding officer may:
(1) Require the cross-examiner to outline the intended scope of the cross-examination;
(2) Prohibit parties from cross-examining witnesses unless the presiding officer has determined that the cross-examiner has an adverse interest on the facts at issue to the party-witness or the party presenting the witness. For the purposes of this subsection, the Assistant Administrator's or his or her representative's interest shall be considered adverse to all parties;
(3) Limit the number of times any party or parties having a common interest may cross-examine an “adverse” witness on the same matter; and
(4) Exclude cross-examination questions that are immaterial, irrelevant or unduly repetitious.
(b) Any party shall be given an opportunity to appear, either in person or through an authorized counsel or representative, to cross-examine witnesses. Before cross-examining a witness, the party or counsel shall state his or her name, address and occupation. If counsel cross-examines the witness, counsel shall state for the record the authority to act as counsel. Cross-examiners shall be assumed to be familiar with the direct testimony.
(d) Scientific, technical or commercial publications may only be utilized for the limited purposes of impeaching witnesses under cross-examination unless previously submitted and introduced in accordance with these regulations.