‘SARA-FRACTION’: Senate redraws conviction math in Duterte impeachment trial

Two-thirds of 20. Maybe 13, maybe 14?

That is the new magic number to convict Vice President Sara Duterte. The Senate, sitting as the impeachment court, voted on Wednesday, Sept. 23, Day 29 of the trial, to reinterpret the two-thirds conviction threshold.

The chamber voted 14-1 in favor of the Sept. 8 motion of Sen. Erwin Tulfo to reconsider how the two-thirds conviction threshold should be calculated.

The ruling means that only senators who have participated in the impeachment court’s proceedings can vote.

Under the new calculation, four senators cannot vote on conviction. They are Ronald “Bato” dela Rosa, who is in hiding; Jinggoy Estrada and Rodante Marcoleta, who are detained; and Loren Legarda, who is on medical leave.

Of the four, only Dela Rosa, who has been absent from the chamber since May 13, did not take his oath as a senator-judge.

Estrada, Marcoleta, and Legarda all took their oath on May 18. Estrada was later arrested on June 1 and Marcoleta on July 6, while Legarda went on leave on Aug. 2.

Only Sen. Francis Escudero, the impeachment court’s presiding officer, voted against Tulfo’s motion.

Aside from Erwin Tulfo, the senators who voted in favor were Bam Aquino, JV Ejercito, Risa Hontiveros, Panfilo “Ping” Lacson, Lito Lapid, Kiko Pangilinan, Vicente “Tito” Sotto III, Raffy Tulfo, Joel Villanueva, Mark Villar, Juan Miguel Zubiri, and Senate President Sherwin Gatchalian.

Article XI, Section 3(6) of the 1987 Constitution states, among others, that “No person shall be convicted without the concurrence of two-thirds of all the Members of the Senate.”

On July 6, at the start of the trial proceedings, Escudero ruled that the threshold was 16, or two-thirds of the 24 senators of the 20th Congress.

During the Sept. 16 session, the Senate heard from amici curiae, or “friends of the court,” on Tulfo’s motion. They were former Chief Justices Artemio Panganiban, Reynato Puno, and Hilario Davide Jr., and former Associate Justice Adolfo Azcuna.

Panganiban, Puno, and Azcuna appeared in person before the impeachment court, while Davide submitted a memorandum.

Citing the unique character of the threshold vote and the lack of legal precedent, Escudero ruled that the decision was pro hac vice, or for this one occasion only. It applies to the Duterte trial and not to future impeachment trials.

Sens. Alan Peter Cayetano, Pia Cayetano, Christopher “Bong” Go, Imee Marcos, Robin Padilla, and Camille Villar did not take part in the vote on the threshold question.

Alan Peter Cayetano had earlier sought to defer deliberation on the threshold, saying the chamber should no longer revisit Escudero’s July 6 ruling.

The Senate voted to proceed with deliberating on Tulfo’s motion anyway. The same six senators voted against proceeding, Mark Villar abstained, and the remaining 13 voted in favor.

SENATORS’ MANIFESTATIONS

Erwin Tulfo defended his motion, particularly its timing. He said the non-participation of Dela Rosa, Estrada, Legarda, and Marcoleta was not an issue when the impeachment court convened.

“It is just appropriate now that we have to examine how these new events affect the computation of the two-thirds vote that the Constitution asks for,” Tulfo said.

“Had the framers [of the Constitution] intended an immutable number, they would have expressly indicated a numerical figure, because it is a fraction. The mathematical baseline dynamically moves or varies depending on structural, operational, situational factors affecting the Senate composition,” he added.

Camille Villar broke into tears as she voiced her dismay at how her absent colleagues were being mentioned, and she urged the chamber to give them grace.

“The senators that are being detained and who are not here right now, that is not their choice, and I think that it is unfair to call them out, for their crimes of plunder and of theft, because none of those senators have been convicted,” Villar said.

“There are a lot of questions about why they are not even here in the first place, and as the youngest member of this august body, can we stop it with these attacks on each other? We are senators of the Philippines; let us give each other due respect. Let us give Filipinos due respect,” she added, audibly tearing up.

Sotto said in his manifestation that if any of the four absent senators return, they could participate, and the voting threshold could rise again.

The chamber’s most senior senator moved to amend the motion so that the threshold would be computed from the senators able to vote. The amendment was incorporated into the final question put to a vote.

“We are now 20 here present. If [Legarda] arrives from abroad, she can vote. If [Dela Rosa] decides to appear and takes his oath, he can vote. If the Sandiganbayan allows [Estrada and Marcoleta] to attend, they can vote,” Sotto said.

“To those who are within the coercive powers of the Senate, two-thirds vote. Not 16, not any other number, two-thirds. That is clear,” he added.

ORAL ARGUMENTS

Before the vote, the prosecution and defense panels presented their oral arguments.

Akbayan Party-list Rep. Chel Diokno argued for the prosecution. His argument centered on the premise that “two-thirds is two-thirds,” and that the Constitution does not refer to a specific number.

Diokno anchored the accountability of public officers on two “sides” — the answerability of officials and employees, and the responsibility of institutions to exact accountability. He also emphasized the sui generis nature of the country’s impeachment process.

“[W]hen senators sit for that purpose, the Constitution specifically requires them to take an oath or affirmation. Why? Because you are not dealing with ordinary legislative business. You are exercising an extraordinary constitutional function as an impeachment court, and this is the only time in the Constitution that members of the Senate are required to take an oath separate from the oath they took when they assumed their office,” Diokno said.

“Viewed through the lens of accountability, therefore, the threshold question is not merely, ‘What is the easiest arithmetic?’ The question is, what interpretation faithfully allows the institutions involved to perform the responsibilities the Constitution has assigned to them while respecting the safeguards the Constitution has itself imposed,” he added.

Diokno said the prosecution’s position is that only senators who participated in the trial should vote on conviction.

He cited the 1949 case Avelino v. Cuenco, in which the Supreme Court ruled that a quorum is determined by the number of members within the Senate’s coercive power. In that case, one of 24 senators was abroad, and 12 of the remaining 23 were held to constitute a quorum.

The same case was cited during the Senate quorum controversies in the brief but loud leadership struggle in June.

Diokno also addressed Bayan v. Zamora, the 2000 case on the Visiting Forces Agreement with the United States, in which the Supreme Court said two-thirds of the Senate was 16 for treaty ratification. He argued that the figure was an “arithmetical illustration of unquestionable compliance” and not a voting threshold.

“Judges’ active participation is very important in a trial. An impeachment trial comprises scrutinizing the fitness of an official. How can it be done by a senator who could not have been a judge because they did not take their oath? How can it be done by a judge who was not in the hearings to examine the witnesses and the documents?” the lawmaker argued.

“Is it not the Constitution’s mandate to hold officials accountable to the people at all times? Is it not that in an impeachment case, those who represent the public are you, the senator-judges? Who will the impeached official face and answer to if the judge is absent or unavailable? A vacant chair or a cold table?” he added.

Diokno argued that even if the number changes with fewer participating senators, it still falls within the two-thirds threshold. He added that fewer votes needed to convict also means fewer votes are needed to acquit.

“A change in the denominator should not be described as simply lowering the votes needed to convict, because the arithmetic moves in both directions. If twenty-four senators are counted, 16 votes are required to convict. Nine votes prevent conviction,” he explained.

“Suppose the court determines that 20 senators should be counted. Two-thirds of twenty will require 14 votes to convict. But what is sometimes, if not often, omitted from this discussion is that seven votes would prevent conviction. So, a different denominator does not guarantee conviction; it changes the arithmetic on both sides,” he added.

Answering a question from Alan Peter Cayetano, the former law dean said the rules requiring trial judges to participate in proceedings should also apply to the impeachment court.

“The judge of a court where a case is pending, the general rule is that they can only participate, and eventually vote, if they heard and personally received the evidence. The only exception recognized is when a judge replaces another judge or is detailed to another court and now has the duty to decide cases that he or she did not hear himself or herself,” Diokno said.

“In this particular case, we are not talking about a judge who was suddenly assigned to the impeachment court, but rather, we are speaking of all the members of the honorable Senate impeachment court, only that some of them are not here for one reason or another, and I believe we must face that reality,” he added.

Lawyer Michael Poa argued for the defense on two main points. First, Escudero had already ruled on the threshold, and the ruling should not be revisited. Second, even if it could be revisited, the threshold should remain at 16.

On the first point, Poa cited Rule VI of the Senate’s Rules of Procedure on Impeachment Trials, which requires motions for reconsideration to be raised at the earliest opportunity.

He also cited the suppletory application of Section 91, Rule XXXIII of the Rules of the Senate, which gives senators only two days to seek reconsideration of a measure the body has decided. He added that several provisions of the Rules of Court give parties 15 days to file a motion for reconsideration.

Poa said that if the motion were given credence, all of the presiding officer’s rulings could be challenged indefinitely or modified arbitrarily.

“Your honors, if that would be our rule here, then even the ruling on issuing subpoenas on bank records can be reopened and voted on, [or] the rulings of the presiding officer on every objection can be returned to,” Poa said.

“That should not be done because the parties must be able to rely on the rulings of the presiding officer; otherwise, that will run contrary to the basic principle of what is an orderly conduct of a fair trial,” he added.

He also warned that granting the motion would raise due process concerns for the vice president.

“If we lower the voting threshold when trial is already underway, […] that will go beyond the procedural [rules]. That will raise questions if [Duterte] is afforded due process guaranteed by the Constitution, […] which according to the Supreme Court in Duterte vs. HOR, must be present at every stage of the proceeding,” the lawyer said.

The Supreme Court’s July 2025 ruling in Duterte v. House of Representatives voided the first impeachment complaint against the vice president. In that ruling, the court held that due process applies at every stage of impeachment proceedings.

On the second point, Poa said the constitutional language on the two-thirds threshold is clear. He argued that the threshold should remain at 16 even if a Senate seat is vacant.

He contrasted the Philippine rule with the impeachment threshold of the U.S. Senate.

Article I, Section 3, Clause 6 of the U.S. Constitution states that “[…] no Person shall be convicted without the Concurrence of two thirds of the Members present.”

Poa also cited the 2012 impeachment trial of then-Chief Justice Renato Corona. Only 23 senators took part in that trial because the seat of Benigno “Noynoy” Aquino III had been vacant since he became president in 2010.

Despite the vacancy, the threshold remained at 16. Corona was convicted on May 29, 2012, with 20 votes to convict and three to acquit.

The defense counsel said Avelino should not be the basis for the decision because it dealt only with a legislative quorum. He argued that Bayan should be more controlling because the constitutional language on treaty concurrence mirrors that on impeachment.

Article VII, Section 21 of the 1987 Constitution provides that “No treaty or international agreement shall be valid and effective unless concurred in by at least two-thirds of all the Members of the Senate.”

“That begs the question: Why is it that when it came to the impeachment of Chief Justice Corona, the threshold was not lowered, but when it comes here to the impeachment of [Duterte], even without a vacancy, lowering the threshold is being discussed?” Poa averred.

Poa noted that absent senators can read the records, review the journals, and watch the trial on video.

He extended his argument to other matters the Senate votes on, warning that the ruling could affect the extension of martial law, the expulsion of a senator, and even constitutional amendments.

“Yes or no are not the only votes. [Senator-judges] may abstain [or] may inhibit, but we have to emphasize that abstention or inhibition do not create vacancies, and therefore it should not affect the denominator. The denominator remains [at] 24, two-thirds of which is 16,” the lawyer said.

Responding to a question from Aquino, Poa confirmed that the defense would elevate the matter to the Supreme Court if the chamber voted to lower the threshold.

AFTERMATH

After the vote, Duterte’s lead counsel, Sheila Sison, said the defense would participate in the trial ad cautelam, or with caution, signaling a possible court challenge.

“Let it be clear that [Duterte] does not [shirk] from accountability, nor does she fear the outcome of this impeachment trial. She asks for nothing spectacular from this court, only the most essential, and the most basic guarantees due to the individual—fairness and impartiality—in a court that is bestowed with the principles duly cared for under the Constitution,” Sison said.

“[E]ven as we understand that this tribunal will proceed as it deems fit, we nonetheless are constrained to put on record that from this day forward, the respondent’s participation or any participation that the respondent will have in this trial will be done with caution or ad cautelam.”

“[Duterte] reserves every right to exhaust all legal remedies available under the law and the Constitution that go to the essence of a truly free democratic institution, and it is the right of every citizen to be heard in a court that has no lean or fear, and will strongly stand in a trial, and in the end a decision, that is just,” she added.