How many votes are needed to convict or acquit in an impeachment trial?
As the Senate prepares for the impeachment trial of Vice President Sara Duterte, uncertainty looms over how many of its 24 members will participate in the tribunal.
Senator Ronald “Bato” dela Rosa remains out of public view following an International Criminal Court arrest warrant, while Senator Jinggoy Estrada is currently detained under a 90-day preventive suspension for a non-bailable plunder charge.
These absences raise questions about how the vacancy and suspension will factor into the mandatory two-thirds vote required for a conviction.
Article XI, Section 3(6) of the 1987 Constitution states that "No person shall be convicted without the concurrence of two-thirds of all the Members of the Senate."
UP College of Law Assistant Professor Michael Tiu Jr. emphasizes that the base number remains 24 regardless of whether certain senators can fulfill their duties.
"In my view, the base number is still 24. This cannot be adjusted because the text is clear. There is no room for interpretation of 'all its Members,'" Tiu told PhilSTAR L!fe.
Corroborating this, Prof. Dennis Coronacion, chairman of the UST Department of Political Science, pointed to the legal principle of verba legis (plain meaning rule), which holds that when a law's wording is clear and unambiguous, it must be applied as written without adding to or altering its meaning. He noted that the framers deliberately used "all the Members" instead of "Members present" as an institutional safeguard.
"Allowing the threshold to shrink whenever a senator is suspended, jailed, or missing would create a dangerous political vulnerability," Coronacion explained.
This constitutional threshold creates an operational dilemma regarding how to treat the votes of absent senators. Tiu noted that while the detained Estrada could vote if given the tools to monitor the trial, Dela Rosa cannot participate unless he appears physically, adding, "If he votes in absentia, that will be an issue they will debate."
For his part, Coronacion said the defense may insist on a fixed 24-senator base requiring 16 votes to convict, while the prosecution may argue that incapacitated or absent senators should be excluded, which lowers the threshold.
"If senators are currently under preventive suspension, detained on criminal charges, or otherwise physically absent, the defense will argue that the denominator must remain fixed at the full 24 constitutionally mandated seats, requiring exactly 16 votes to convict. On the other hand, the prosecution may attempt to adopt a flexible and realistic threshold, arguing that senators who are legally disabled from performing their duties should be excluded from the total pool, thereby lowering the target number of votes needed for a conviction," he said.
However, Senate President Sherwin Gatchalian has affirmed that he will uphold the 16-vote requirement, regardless of how many senators are present.
Duterte faced a total of four impeachment complaints. The first complaint was filed by a coalition of various organizations on Dec. 2, 2024, but was set aside for violating the one-year bar rule. The second was filed on Dec. 4 of the same year, but was withdrawn to consolidate support for the third complaint.
The third complaint, backed by ML Party-list Rep. Leila de Lima, charged Duterte with culpable violation of the Constitution, betrayal of public trust, plunder or malversation, bribery, graft and corruption, and other high crimes.
The fourth complaint, endorsed by House Deputy Speaker Paolo Ortega and Manila 6th District Rep. Bienvenido Abante, similarly alleged constitutional violations, betrayal of public trust, graft and corruption, and other impeachable offenses.
The House lawmakers voted 257 in favor of her impeachment during its first regular session on May 11. Twenty-five voted against it, while nine abstained.
If the Senate impeachment court finds her guilty of the charges, Duterte will be removed from her current post and permanently barred from holding public office.
