Unless otherwise ordered and noticed, hearings shall be held as a part of the regular meetings of the Council. The hearing shall be de novo in that an independent reexamination of the matter shall be made. The appellant shall have the burden of proof in all cases, and where it appears that an appellant was served with a notice of hearing but fails to appear either in person or by counsel, or fails to present or offer evidence, the Council may adopt the determination or approve the act of the board, commission, or official, or it may itself decide the matter upon the record with or without taking any additional evidence. Any oral or documentary evidence may be received, but the Mayor shall exclude irrelevant, immaterial, or unduly repetitious evidence. Unless a demand is made, witnesses will not be sworn. It shall not be a ground for objection that the evidence is hearsay or secondary, however, the Council's decision shall be made upon substantial evidence. (1962 Code § 1-6.106)