MANILA — Retired Supreme Court justices offered differing interpretations Wednesday on how the two-thirds voting requirement for convicting Vice President Sara Duterte should be applied in her impeachment trial.

Retired Chief Justice Hilario Davide Jr. argued in a legal memorandum that the threshold should be based on the number of senators qualified to vote, rather than the Senate’s full 24-member membership.

Retired Chief Justice Reynato Puno likewise rejected a fixed 16-vote threshold, saying the constitutional provision does not necessarily make the required number immutable.

Puno said the phrase “two-thirds of all the members of the Senate” under Article XI, Section 3(6) means the number of votes required may vary depending on certain factors.

“If we give this kind of reading to Article 11, Section 3(6), the threshold of 16 senators to convict will be fixed and immutable… However, if that is the intent, Article 11, Section 3(6) should have simply stated that the number of votes to convict is 16. Period.”

Retired Associate Justice Adolfo Azcuna took a different position, maintaining that the Constitution requires two-thirds of the Senate’s full membership to convict in an impeachment case.

“The reference in this provision is to all members of the Senate, as long as they are members of the Senate, they constitute the denominator and computing threshold of two-thirds because all means all,” he said on Wednesday.

Azcuna also rejected computing the threshold based on the number of senators participating in the proceedings.

“For example, if there are only 20 who are participating, two-thirds of 20 would effectively become 13 or 14, so that would be really simple majority. That is not the purpose of the internal check of a threshold. A threshold must be fixed, not variable. It must be determinable from the start,” he said on Wednesday.

Retired Chief Justice Artemio Panganiban, meanwhile, underscored the importance of active participation by senator-judges in the impeachment proceedings.

“The Senate’s mandate demands a commonsensical interpretation of the Constitution. Indeed, meaningful adjudication requires active participation in the search for truth and fairness,” Panganiban said Wednesday.

Panganiban, Puno and Azcuna appeared before the Senate impeachment court as amici curiae, or friends of the court, to assist in resolving the interpretation of the constitutional provision on the required votes for conviction.

Presiding Officer Sen. Francis “Chiz” Escudero earlier announced their participation in the Sept. 16 proceedings.

“For the information of the parties and the public, the court formally announces that, as discussed during the trial of Sept. 10, 2026, it has secured the participation of the following legal luminaries as amici curiae on the meaning of all members under Article 11, Section 3-6 of the Constitution, as raised by Senator-Judge Erwin Tulfo,” Escudero said.

Article XI, Section 3(6) of the 1987 Constitution provides that an impeachment conviction requires the concurrence of “two-thirds of all the Members of the Senate.”

The Senate is constitutionally composed of 24 members, making two-thirds equivalent to 16 votes.

The impeachment court is considering the proper interpretation of “all the Members of the Senate” and how the provision applies to Duterte’s impeachment trial.