Three retired Supreme Court justices are set to appear personally before the Senate Impeachment Court on Wednesday, September 16, to assist senator-judges in resolving a pivotal constitutional question, whether 16 votes must remain the mandatory threshold to convict Vice President Sara Z. Duterte.
Presiding Officer Sen. Francis Escudero announced Monday that retired Chief Justices Artemio Panganiban and Reynato Puno, alongside retired Associate Justice Adolfo Azcuna, have agreed to serve as amici curiae or friends of the court.
“For the information of the parties and the public, the court formally announces that, as discussed during the trial of September 10, 2026, it has secured the participation of the following legal luminaries as amici curiae on the meaning of all members under Article 11, Section 3-6 of the Constitution, as raised by Senator-Judge Erwin Tulfo,” Escudero stated.
Under Article XI, Section 3(6) of the 1987 Constitution, no official can be convicted in an impeachment proceeding without the concurrence of “two-thirds of all the Members of the Senate.”
In a standard 24-member chamber, that two-thirds requirement translates directly to 16 votes.
However, Senator-Judge Erwin Tulfo raised the issue to seek a definitive legal clarification regarding who counts as part of “all the Members of the Senate” if certain senator-judges are unable to take part in the final vote or proceedings. The determination is critical, as altering the base count of eligible voting members could shift the exact number of votes required to secure a conviction.
While retired Chief Justice Hilario Davide Jr. was also named an amicus curiae, he will not appear in person; his submitted legal memorandum will instead be entered into the official court records.
The inclusion of Azcuna and Davide brings historical authority to the proceedings, as both served as members of the 1986 Constitutional Commission that authored the 1987 Constitution. Davide notably presided over the 2000–2001 impeachment trial of former President Joseph Estrada, while Azcuna served as vice chair of the commission’s committee on accountability of public officers.
Panganiban, Puno and Azcuna will deliver their legal opinions directly to the tribunal on Wednesday. All four former jurists are participating as neutral, independent advisors and are not aligned with either the House prosecution or Vice President Duterte’s defense team.
In addition to the retired justices, Escudero disclosed that the tribunal received a position paper on the threshold question from Fr. Ranhilio Aquino, dean of the San Beda University Graduate School of Law. Escudero confirmed that the court will review Aquino’s arguments and distribute copies of the submission to both parties and the senator-judges.