49 CFR § 1503.645
Expert or opinion witnesses
November 18, 2020
An employee of the agency may not be called as an expert or opinion witness, for any party other than TSA, in any proceeding governed by this subpart. An employee of a respondent may not be called by an agency attorney as an expert or opinion witness for TSA in any proceeding governed by this subpart to which the respondent is a party.