Where respondent does not file an answer, the procedures of this paragraph shall apply. If the petition is based upon an oath made upon personal knowledge, the facts shall be deemed established as alleged in the petition. If the petition is based upon an oath made upon other than personal knowledge, Bar Counsel shall present competent proof of the factual allegations in the petition. A respondent who has not filed an answer may, if present at the hearing, cross-examine Bar Counsel’s witnesses, testify in his own behalf (but not present either the testimony of others or present non-testimonial evidence), file post-hearing briefs on all issues (if called for by the Hearing Committee), and present a plea or testimony in mitigation of sanction.