
Fixed 16-Vote Requirement Replaced by a New Formula
The Senate, sitting as an impeachment court, made a significant procedural ruling on September 23, 2026, changing how the number of votes required to convict Vice President Sara Duterte will be calculated.
By a 13–1 vote, with six senator-judges not participating, the impeachment court overturned its earlier interpretation that automatically required 16 votes for conviction based on the Senate’s full 24-member composition.
Importantly, the constitutional requirement itself has not changed. Article XI, Section 3(6) of the 1987 Constitution requires the concurrence of two-thirds of all the Members of the Senate for conviction. The dispute centers on how the membership used as the denominator should be determined when some senator-judges cannot legally or factually participate.
What Is the New Basis?
Under the new controlling ruling, the two-thirds requirement will be calculated using senator-judges who, at the time judgment is rendered, remain legally and factually capable of participating in the impeachment proceedings.
The ruling provides that senators may be excluded from the denominator under circumstances such as detention or suspension, another legal restraint preventing them from performing their functions, unknown whereabouts while being sought by authorities, physical or medical incapacity, being beyond the Senate’s coercive processes, or comparable situations.
This does not mean that simply being absent automatically removes a senator from the calculation. The relevant legal and factual circumstances must determine whether that senator is capable of participating when the final judgment is taken.
Does This Mean 16 Votes Are No Longer Required?
Not necessarily in every situation.
If all 24 senators are legally and factually capable of participating, two-thirds remains 16 votes.
However, under the new formula, if only 20 senator-judges are counted as capable of participating, two-thirds is 13.33, meaning at least 14 votes would be needed to reach the two-thirds threshold. Reports following the September 23 ruling indicated that, under the present circumstances, 14 votes would be required rather than the previously fixed 16.
The exact threshold could therefore change depending on the number of senator-judges legally and factually capable of participating when the verdict is rendered.
Why Is the Ruling Significant?
At the center of the controversy is the constitutional phrase:
“two-thirds of all the Members of the Senate.”
Those supporting the new interpretation distinguish between the constitutional two-thirds requirement—which remains intact—and the number of senators who should form the voting base when some members cannot participate. Senate President Sherwin Gatchalian, for example, said the issue concerned which senators should be counted in the base, rather than changing the constitutional two-thirds standard itself.
Opponents have presented a different constitutional interpretation. Some senator-judges argued that “all the Members of the Senate” refers to the Senate’s full membership and that the denominator should therefore not be reduced because particular members are unable to participate.
The defense of Vice President Duterte had also argued before the vote that the earlier 16-vote ruling should remain in effect and was not subject to appeal. After the new ruling was adopted, her defense said it was considering bringing the issue before the Supreme Court.
What Happens Next?
The impeachment trial continues, and the prosecution says the new threshold does not change its responsibility to present evidence and prove the Articles of Impeachment.
The voting-threshold controversy may also continue outside the Senate if the ruling is challenged before the Supreme Court.
For now, the key point is clear: the constitutional two-thirds requirement remains, but the Senate Impeachment Court has changed how the number of senator-judges forming the basis of that calculation will be determined.
The final number required for conviction will depend on who is legally and factually capable of participating when judgment is rendered.
What is your understanding of the phrase “two-thirds of all the Members of the Senate”? Share your views respectfully in the comments.
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