(a) When acting as a court of record, the Commission shall apply the rules of evidence applicable in civil actions in the superior court, insofar as practicable, but no decision or order of the Commission shall be made or entered in any such proceeding unless the same is supported by competent material and substantial evidence upon consideration of the whole record. Oral evidence shall be taken on oath or affirmation. The rules of privilege shall be effective to the same extent that they are now or hereafter recognized in civil actions in the superior court. The Commission may exclude incompetent, irrelevant, immaterial and unduly repetitious or cumulative evidence. All evidence, including records and documents in the possession of the Commission of which it desires to avail itself, shall be made a part of the record in the case by definite reference thereto at the hearing. Any party introducing any document or record in evidence by reference shall bear the expense of all copies required for the record in the event of an appeal from the Commission's order. Every party to a proceeding shall have the right to call and examine witnesses, to introduce exhibits, to cross‑examine opposing witnesses on any matter relevant to the issues, to impeach any witness regardless of which party first called such witness to testify and to rebut the evidence against him. If a party does not testify in his own behalf, he may be called and examined as if under cross‑examination.
(b) The Commission may take judicial notice of its decisions, the annual reports of public utilities on file with the Commission, published reports of federal regulatory agencies, the decisions of State and federal courts, State and federal statutes, public information and data published by official State and federal agencies and reputable financial reporting services, generally recognized technical and scientific facts within the Commission's specialized knowledge, and such other facts and evidence as may be judicially noticed by justices and judges of the General Court of Justice. When any Commission decision relies upon such judicial notice of material facts not appearing in evidence, it shall be so stated with particularity in such decision and any party shall, upon petition filed within 10 days after service of the decision, be afforded an opportunity to contest the purported facts noticed or show to the contrary in a rehearing set with proper notice to all parties; but the Commission may notify the parties before or during the hearing of facts judicially noticed, and afford at the hearing a reasonable opportunity to contest the purported facts noticed, or show to the contrary. (1949, c. 989, s. 1; 1959, c. 639, s. 2; 1963, c. 1165, s. 1; 1973, c. 108, s. 21.)