40 CFR 104.9 - Admission of evidence.
(a) Where the Presiding Officer has directed identification of witnesses and production of documentation evidence by a certain date, the Presiding Officer may exclude any such evidence, or refuse to allow any witness to testify, when the witness was not identified or the document was not served by the time set by the Presiding Officer. Any such direction with respect to a party's case in chief shall not preclude the use of such evidence or testimony on rebuttal or response, or upon a showing satisfactory to the Presiding Officer that good cause existed for failure to serve testimony or a document or identify a witness by the time required. The Presiding Officer may require direct testimony to be in writing under oath and served by a certain date, and may exclude testimony not so served.
(b) At the first prehearing conference, or at another time before the beginning of the taking of oral testimony to be set by the Presiding Officer, the statement of basis and purpose, together with any publications or reference materials cited therein, except where excluded by stipulation, shall be received in evidence.
(c) The Presiding Officer may exclude evidence which is immaterial, irrelevant, unduly repetitious or cumulative, or would involve undue delay, or which, if hearsay, is not of the sort upon which responsible persons are accustomed to rely.
(e) Whenever written testimony or a document or object is excluded from evidence by the Presiding Officer, it shall at the request of the proponent be marked for identification. Where oral testimony is permitted by the Presiding Officer, but the Presiding Officer excludes particular oral testimony, the party offering such testimony may make a brief offer of proof.
(f) Any relevant and material documentary evidence, including but not limited to affidavits, published articles, and official documents, regardless of the availability of the affiant or author for cross-examination, may be admitted in evidence, subject to the provisions of paragraphs (a), (c), and (d) of this section. The availability or nonavailability of cross-examination shall be considered as affecting the weight to be accorded such evidence in any decision based upon the record.