Sixteen votes and the meaning of two-thirds

The constitutional dispute is ultimately about whether a fixed Senate denominator can cause a two-thirds requirement to operate as a substantially higher threshold

By Francis Allan L Angelo and Joseph Ledesma Ladrido

The impeachment trial of Vice President Sara Duterte has raised a constitutional question that appears to require little more than arithmetic. Article XI, Section 3(6) of the 1987 Constitution provides that “no person shall be convicted without the concurrence of two-thirds of all the Members of the Senate.” With 24 Senate seats, two-thirds produces 16 votes. Presiding Officer Francis Escudero adopted that interpretation at the beginning of the trial.

The arithmetic becomes less straightforward when some senators cannot participate. Four are presently absent from the proceedings under different circumstances, prompting Senator Erwin Tulfo to ask the impeachment court to reconsider what “all the Members of the Senate” means in determining the denominator for conviction.

Describing this as an attempt to “lower” the threshold assumes the answer. The Constitution does not prescribe 16. It prescribes two-thirds of all the Members of the Senate. Sixteen follows only if the constitutionally relevant denominator is 24.

THE CASE FOR SIXTEEN

The fixed-24 interpretation has the strongest textual foundation. The Constitution does not say two-thirds of senators present, voting or participating as senator-judges. It says two-thirds of all the Members of the Senate. Retired Supreme Court Justice Adolfo Azcuna, a member of the 1986 Constitutional Commission, has argued accordingly that suspension or detention does not necessarily terminate Senate membership. ¹

Bayan v. Zamora provides important jurisprudential support. The case concerned another constitutional provision requiring concurrence by two-thirds of all Senate members. Although only 23 Senate seats were then occupied, the Supreme Court treated 16 votes as the required concurrence, effectively calculating the threshold against the Senate’s full complement of 24.²

There is also good institutional reason to resist an attendance-based denominator. If senators could change the threshold simply by appearing, withdrawing or boycotting proceedings, a constitutional supermajority designed to constrain political power could itself become susceptible to political manipulation.

The fixed-24 interpretation therefore begins from strong ground. Its difficulty arises when a senator is not merely absent but legally incapable of exercising the office.

CARPIO’S LEGAL-CAPACITY TEST

Retired Supreme Court Senior Associate Justice Antonio Carpio draws precisely that line. A senator who is ill, abroad, politically boycotting proceedings or otherwise absent ordinarily retains the legal authority to act as a senator. Carpio has accordingly distinguished Senator Ronald dela Rosa’s situation: absence or exposure to arrest does not itself suspend or remove him from office.

A senator subject to a valid legal prohibition against exercising public office presents a different case. Preventive suspension may leave the person formally holding the office while preventing the exercise of its powers. Voting is one of those powers.

Carpio’s proposition is therefore narrower than an attendance rule: **absence does not change the denominator; legal incapacity potentially does. **³

That limiting principle gives his argument considerable force. Senators cannot change the threshold by staying away. The denominator changes only when the legal system itself changes a senator’s capacity to exercise senatorial power.

WHEN TWO-THIRDS BECOMES FOUR-FIFTHS

Former Integrated Bar of the Philippines president Domingo Cayosa advances a broader argument based on senators’ adjudicative role in an impeachment trial. His participation-based approach is less persuasive because the Constitution provides no workable standard for determining how much of the trial a senator must attend before qualifying as a senator-judge. Such a rule could also make the denominator vulnerable to strategic absence. ⁴

Cayosa nevertheless identifies a serious consequence of an inflexible 16-vote requirement.

With 24 senators legally capable of voting, 16 represents 66.67 percent. If only 22 can legally vote, 16 represents 72.73 percent. With 20, it becomes 80 percent. With 18, 88.89 percent. If only 16 senators can legally vote, conviction requires unanimity; with 15, conviction becomes impossible even if every senator legally entitled to vote favors it.

These scenarios could therefore be understood as effectively changing the constitutionally prescribed two-thirds threshold as the pool of legally available votes contracts; conversely, because the Constitution requires concurrence by “at least two-thirds,” they can also be read as merely making the constitutional minimum progressively harder to attain rather than altering it.

The critical issue is why the votes are unavailable. If four senators simply refuse to attend, 24 lawful votes still exist and four have gone uncast. Requiring 16 has not changed the constitutional rule.

Legal incapacity is different. If the law itself prohibits four senators from exercising their office, only 20 lawful votes can be cast. A fixed requirement of 16 then remains two-thirds of the nominal 24-member denominator while becoming four-fifths of every legally possible vote.

The difference is between a vote that could have been cast but was not and a vote that could not lawfully have been cast at all.

WHAT BAYAN DOES NOT ANSWER

Bayan v. Zamora remains the strongest obstacle to Carpio’s interpretation, but the case involved a vacancy. There was no 24th incumbent whose legal capacity to exercise office had been suspended. The Court nevertheless calculated the threshold against the constitutionally constituted 24-seat Senate.

The present controversy can involve a different legal condition: an occupied Senate seat whose incumbent remains formally a senator but is prohibited from exercising the powers of office. Bayan does not establish that these situations must be treated differently, but neither does it squarely establish that they are constitutionally identical.

This is also why the four absent senators cannot simply be subtracted from 24. Their circumstances must be assessed separately. Absence, detention, medical incapacity, an outstanding arrest warrant and legal suspension do not necessarily have the same consequence for the exercise of senatorial power.

SIXTEEN IS PRESUMPTIVE, NOT IMMUTABLE

The competing arguments support a reasonably clear conclusion. Sixteen should remain the threshold whenever 24 senators retain the legal capacity to exercise senatorial office, regardless of how many actually attend or vote. It should not necessarily remain the threshold when a valid legal process has rendered one or more sitting senators legally incapable of exercising that office.

This interpretation gives effect to both parts of the constitutional command. “All the Members of the Senate” prevents ordinary absence or political maneuvering from changing the denominator. “Two-thirds” establishes the degree of concurrence required for conviction and weighs against allowing legal incapacity to turn that requirement progressively into three-fourths, four-fifths or unanimity.

Carpio therefore offers the stronger rule for the exceptional case. Start with 24. Count every senator who remains legally capable of exercising senatorial office, present or absent. Exclude only a senator whom a valid legal process has actually disabled from exercising the office. Apply two-thirds to the resulting denominator.

Cayosa’s participation theory reaches too far, but the arithmetic problem he identifies strengthens Carpio’s narrower argument. An inflexible denominator can eventually cause a constitutional requirement expressed as two-thirds to demand substantially more than two-thirds of every vote the law allows to be cast.

This does not establish that four absent senators reduce the denominator to 20. One legally excluded senator would leave 23 and still require 16 votes. A denominator of 22 would require 15; 21 would require 14. The legal status of each senator therefore matters.

The Senate is ultimately deciding something more important than whether Sara Duterte’s conviction should require 16, 15 or 14 votes. It is establishing a constitutional rule that must remain coherent when the political alignments are reversed and when future Presidents, Vice Presidents or other impeachable officials are tried.

Sixteen is the presumptive threshold, not an immutable one. When the legally relevant denominator is 24, the Constitution requires 16. When lawful incapacity changes that denominator, the Constitution still requires what it actually says: two-thirds.

WHERE THIS LEAVES THE 16-VOTE QUESTION

Sixteen therefore remains the presumptive threshold, but it should not necessarily be treated as immutable when senators are legally incapable of exercising their office. Absence alone should not change the denominator; legal incapacity presents the stronger case for doing so. The Senate must ultimately determine who legally counts before it can determine how many votes two-thirds requires.

***

Endnotes

1. Azcuna, A. S. Public commentary on the constitutional meaning of “all the Members of the Senate” in relation to senators unable to participate in an impeachment trial, 2026.
2. Bayan v. Zamora, G.R. No. 138570, October 10, 2000.
3. Carpio, A. T. Public commentary and interviews concerning the constitutional voting denominator and legal capacity to exercise senatorial office, 2026.
4. Cayosa, D. E. Public commentary concerning participation by senator-judges and the constitutional denominator, 2026.

Disclosure: This article is based solely on open-source and publicly available information, including official records, court and legislative materials, public statements, published reports, and other information available to the general public. It does not rely on confidential briefings, private communications, or information provided directly by any individual, counsel, senator-judge, government office, political actor, or institution participating in or connected to the impeachment trial.