39 C.F.R. § 957.10
The Hearing Officer may approve or disapprove witnesses in his or her discretion. All testimony will be taken under oath or affirmation, and subject to cross-examination. The Hearing Officer may exclude evidence to avoid unfair prejudice, confusion of the issues, undue delay, waste of time, or presentation of irrelevant, immaterial, or cumulative evidence. Although the Hearing Officer will consider the Federal Rules of Evidence for guidance regarding admissibility of evidence and other evidentiary issues, he or she is not bound by those rules. The weight to be attached to evidence presented in any particular form will be within the discretion of the Hearing Officer, taking into consideration all the circumstances of the particular case. Stipulations of fact agreed upon by the parties may be accepted as evidence at the hearing. The parties may stipulate the testimony that would be given by a witness if the witness were present. The Hearing Officer may in any case require evidence in addition to that offered by the parties. A party requiring the use of a foreign language interpreter allowing testimony to be taken in English for itself or witnesses it proffers is responsible for making all necessary arrangements and paying all costs and expenses associated with the use of an interpreter.
39 C.F.R. §957.10