EXPLAINER: How Many Votes to Convict Sara Duterte? The Constitutional Arithmetic the Senate Must Now Resolve

By Marcial Bonifacio

9/16/26

My friends and countrymen, the impeachment trial of Vice President Sara Duterte has been underway since July 6, 2026, and before a single article of impeachment has been decided on its merits, the Senate impeachment court has been forced to confront a question that may determine the outcome of the entire proceeding: how many senator-judges must vote "guilty" in order to convict?

The answer appears straightforward. Article XI, Section 3, Paragraph 6 of the 1987 Philippine Constitution states that no person shall be convicted "without the concurrence of two-thirds of all the Members of the Senate." The Senate is composed of 24 members. Two-thirds of 24 is 16. On the opening day of the trial, Presiding Officer Senator Francis Escudero ruled accordingly: 16 votes are required for conviction, and no senator-judge challenged or appealed that ruling at the time.

The matter did not remain settled for long. As the trial progressed, four senator-judges became unable or unwilling to participate. Senator Jinggoy Estrada was arrested and detained on plunder charges. Senator Rodante Marcoleta was likewise arrested on separate plunder charges. Senator Ronald "Bato" dela Rosa has been in hiding since May, evading an arrest warrant issued by the International Criminal Court for his alleged role in former President Rodrigo Duterte's drug war. Senator Loren Legarda has been absent on medical leave since August 3, with the Office of the Ombudsman announcing a preliminary investigation against her for graft and plunder over alleged anomalous solar projects.

With four of 24 senator-judges effectively absent, the question became unavoidable: should the conviction threshold remain at 16, or should it be recalculated to reflect only those senators who are legally qualified and physically able to participate?

On September 8, 2026, Senator Erwin Tulfo formally appealed Escudero's July 6 ruling, asking the impeachment court to revisit the threshold. Tulfo maintained that his appeal was not intended to lower the bar for conviction, but to clarify whether senators who cannot participate should continue to be counted among "all the Members of the Senate" as the Constitution uses that phrase.

The impeachment court has invited four retired Supreme Court justices as amici curiae, or "friends of the court," to advise on the matter. Three of them are scheduled to appear physically before the court on September 16: retired Chief Justices Artemio Panganiban and Reynato Puno, and retired Associate Justice Adolfo Azcuna. Retired Chief Justice Hilario Davide Jr., who presided over the impeachment trial of former President Joseph Estrada in 2000, will submit a legal memorandum rather than appearing in person. Notably, both Davide and Azcuna were framers of the 1987 Constitution. The prosecution and defense will present oral arguments on September 23, after which the senator-judges are expected to vote.

What follows is a presentation of the competing positions, sourced from the officials and legal authorities who have stated them publicly.

Those Who Argue the Threshold Must Remain at 16

The textualist position holds that the Constitution means precisely what it says. "All the Members of the Senate" refers to the total composition of the chamber, which is 24. Two-thirds of 24 is 16. The threshold does not move.

Presiding Officer Francis Escudero established this reading on July 6, 2026, when he ruled that conviction requires at least 16 affirmative votes based on a literal interpretation of the constitutional provision. He has since invited the amici curiae to weigh in, but his original ruling stands unless overturned by the senator-judges.

Senator Alan Peter Cayetano affirmed the 16-vote requirement on July 7, stating that the court had effectively settled the matter when no senator-judge objected on the first day. Cayetano further argued that senators who are unable to vote would effectively be counted in favor of acquittal, a consequence he suggested might be more favorable to the defense than a reduced threshold.

Acting Senate President Win Gatchalian declared on June 10 that the threshold would remain at 16 "regardless of how many senators attend the trial, which bloc controls the chamber, or who presides over the impeachment court."

The Vice President's camp has publicly agreed with Escudero's ruling, maintaining that the two-thirds requirement refers to the total number of seats in the chamber.

Representative Paolo Duterte, the Vice President's brother, argued on social media that 10 votes cannot amend a constitutional requirement, writing that a bare majority tally "has no bearing on the Constitution."

Senator Pia Cayetano cautioned against treating selective interpretations of Supreme Court decisions as though they were established jurisprudence or Senate rules.

Senator Robin Padilla insisted that constitutional provisions cannot be altered arbitrarily and must undergo standard amendment procedures through proper legislative committees.

Impeachment court spokesman Reginald Tongol, in a separate statement from his procedural clarifications, warned that lowering the constitutionally cited 16-vote requirement would set a "dangerous precedent" and that the court "cannot bend established legal standards for the convenience of any party."

Those Who Argue the Threshold May Be Adjusted

The functional position holds that "all the Members of the Senate" should be understood to mean all members who are legally qualified to exercise the functions of a senator, not those who have been removed from participation by suspension, detention, or flight from the law. Under this reading, the two-thirds calculation changes when the number of qualified members changes.

Retired Supreme Court Associate Justice Antonio Carpio has been the most prominent voice for this position. Carpio's view evolved over the course of the proceedings. In April 2026, he stated that conviction requires 16 affirmative votes regardless of absences, and that senators who do not participate effectively count against conviction because the threshold is fixed. By June 2026, Carpio revised his position, arguing that the threshold is not fixed and will depend on the total number of active senators when the court convenes, because the constitutional computation should include only those legally qualified to participate. Specifically, Carpio argued that suspended Senator Jinggoy Estrada should be excluded from the count, citing Supreme Court rulings and provisions of the Plunder Law. He also maintained that only senators who took their oath should sit as judges, which he said would not include Senator Ronald dela Rosa, who has not resurfaced since slipping out of custody in May 2026.

Retired Associate Justice Adolfo Azcuna, who was one of the framers of the 1987 Constitution, raised a separate basis for reducing the count. Azcuna suggested that dela Rosa could be excluded from the computation if judged a fugitive, arguing that being a fugitive amounts to what he called "constructive resignation." In his words: "Being a fugitive entails running away from the legal system. If one runs away from the legal system, he relinquishes all membership in that system." Under this reasoning, the conviction threshold could drop to 15.

Retired Chief Justice Artemio Panganiban wrote in his Philippine Daily Inquirer column that Escudero's 16-vote ruling is "not set in stone." He described the ruling as "merely interlocutory," meaning the impeachment court can reverse or modify it at the proper time. Panganiban added that such reversal or modification "requires only a simple majority, not two-thirds."

University of the Philippines College of Law Associate Dean and constitutional law professor Paolo Tamase initially held the traditional view, stating in June 2026 that "all the members" requires an absolute two-thirds majority and that conviction remains possible as long as at least 16 senators are available. He subsequently told Rappler that he found Carpio's argument persuasive, noting that the conventional reading "opens the possibility to some Senate functions being incapable of being fulfilled" if the number of functional members drops below the thresholds the Constitution requires. Tamase acknowledged these are "unprecedented times" and concluded that the emerging view "seems persuasive if we intend a functional Senate and functional constitutional processes."

Former Integrated Bar of the Philippines president Domingo Cayosa argued that lowering the threshold to match the number of participating senator-judges would be the "fair and practical" reading of the 1987 Constitution, consistent with its spirit of keeping institutions operative and effective.

Lead Public Prosecutor Representative Gerville Luistro was among the first officials to express support for potentially reducing the required votes to between 14 and 15.

The Procedural Mechanics

Impeachment court spokesman Tongol clarified on September 13 that the court will need 11 votes from the active roster of 20 senator-judges to overturn Escudero's ruling. This corrected his earlier statement that only 10 votes were needed, an error that was carried in national headlines. The correction accounts for the fact that Presiding Officer Escudero is now expected to vote on the threshold question, bringing the active roster to 20 rather than 19. Tongol also explained on September 14 that the court may have to vote twice: first on whether to overturn Escudero's existing ruling, and then, if that vote succeeds, on what the new threshold should be. If the vote to overturn results in a tie, the motion fails and Escudero's 16-vote ruling stands.

The Voices Urging Procedural Integrity

Former Senator Richard Gordon has warned publicly against efforts to block or frustrate the impeachment trial, positioning himself as a voice for procedural legitimacy rather than advocating for a specific threshold number. His commentary has focused on the Senate's constitutional duty to conduct the trial itself.

Former Senate President Franklin Drilon has emphasized that impeachment is a political process, not a criminal case, and that conviction requires a two-thirds vote based on the senators' conscience. "Not all senators are lawyers," Drilon has noted. "Therefore, they cannot act as judges in determining whether there is proof beyond reasonable doubt. What matters is what is in their conscience, and that is what will prevail."

House prosecution spokesman Representative Zia Alonto Adiong has stressed that the two-thirds rule itself is fixed, but that the translation of that rule into an actual number of votes is a matter for the impeachment court to decide. He stated that the prosecution "does not want its case to be driven by vote counting."

The Historical Precedent: The Estrada Trial

This is not the first time the conviction threshold has been debated in the Philippines. During the impeachment trial of former President Joseph Estrada in 2000, news archives indicate that there was initial confusion among lawmakers on whether 15 or 16 votes were needed for removal, as there were only 22 sitting senators at the time. The trial, presided over by Chief Justice Hilario Davide Jr., did not reach a verdict; it was aborted when the senator-judges voted 11 to 10 against opening a sealed envelope containing critical bank records, triggering the public outrage that led to the Second EDSA Revolution.

The unresolved arithmetic of the Estrada trial now returns to the same chamber, with the same constitutional text, and with Davide himself being asked to advise on the very question his predecessors never formally settled.

The American Parallel: "Members Present" vs. "All the Members"

The Philippine Constitution was largely modeled after the Constitution of the United States, and the impeachment clauses of both nations are structurally identical in design, with one critical divergence in the language governing the conviction threshold.

The American text, under Article I, Section 3, Clause 6, reads: "No Person shall be convicted without the Concurrence of two thirds of the Members present."

The Philippine text, under Article XI, Section 3, Paragraph 6, reads: "No person shall be convicted without the concurrence of two-thirds of all the Members of the Senate."

The American framers chose "Members present." The Philippine framers chose "all the Members." That single substitution is the origin of the entire dispute now before the Senate impeachment court.

Under the American system, the two-thirds threshold operates on a sliding scale. If some senators are absent, recused, or the chamber has vacancies, the number needed for conviction adjusts accordingly. The only fixed requirement is that a quorum must be present, which the U.S. Constitution sets at a majority of the chamber, or 51 senators. In theory, a conviction in the United States would count as constitutionally valid with as few as 34 affirmative votes, provided the minimum quorum of 51 senators participated.

This was precisely how the threshold was applied in the first impeachment trial of an American president. In 1868, when the United States Senate tried President Andrew Johnson on eleven articles of impeachment, 54 senators voted on the articles. The result was 35 guilty and 19 not guilty. The tally fell one vote short of the two-thirds of those present required for conviction. No constitutional dispute arose over whether absent senators should have been counted in the denominator, because the American text explicitly limits the calculation to those present.

The Philippine framers studied the American original when they drafted the 1987 Constitution. The parallel structure of the two impeachment clauses confirms this. Both documents name a presiding officer for exactly one scenario (the impeachment of the sitting president; the Chief Justice in both cases). Both documents vest the Senate with the sole power to try all impeachments. Both documents require senators to be under oath. The Philippine framers adopted the American architecture, but on the conviction threshold, they made a specific textual choice: they replaced "Members present" with "all the Members."

That substitution is the heart of the current debate. Those who argue for the fixed threshold of 16 contend that the framers deliberately chose a higher, more rigid standard than the American model, one that cannot be lowered by the absence or incapacity of individual senators. Those who argue for an adjustable threshold contend that "all the Members" was intended to mean all members who are legally qualified to serve, not members who have placed themselves beyond the reach of the legal system through suspension, detention, or flight from justice.

Both sides claim to honor the framers' intent. The fact that two of those framers, Davide and Azcuna, are now among the amici curiae advising the court means the Senate has an opportunity that rarely presents itself in constitutional disputes: the opportunity to ask the authors of the text what they meant when they wrote it.

What Happens Next

The amici curiae will present their views on September 16. The prosecution and defense will argue their positions on September 23. The senator-judges will then vote. Their decision will determine not only whether 16 votes or fewer are required to convict Vice President Sara Duterte, but also whether the Senate, as a constitutional institution, can function when a significant number of its own members are under criminal prosecution or in hiding from the law.

My friends and countrymen, the question before the Senate is not merely one of arithmetic. It is a question of whether the Constitution was written to protect the rights of the accused, to preserve the functional integrity of the institutions it created, or both at the same time, even when those two purposes appear to pull in opposite directions. Two of the men who drafted the relevant provision will soon tell the Senate what they intended. Whether the senator-judges will listen is a separate matter entirely, and that is a question only they can answer.

Long live the rule of law, and long live the Republic of the Philippines!