Amici curiae or “Friends of the Court’ enter VP Sara impeachment debate over conviction threshold

ASM, Philippine Canadian Inquirer
September 16, 2026

Four former Supreme Court justices are taking part in Vice President Sara Duterte’s impeachment proceedings as amici curiae, or “friends of the court,” as the Senate impeachment court tackles a key constitutional question: how many votes are required to convict when some senator-judges are unable to participate.

Retired Chief Justices Artemio Panganiban and Reynato Puno, along with retired Associate Justice Adolfo Azcuna, are scheduled to personally appear before the impeachment court on September 16 to give their legal opinions on the disputed voting threshold.

Retired Chief Justice Hilario Davide Jr. is also participating as an amicus curiae but will submit a written legal memorandum instead of appearing personally. Davide previously presided over the impeachment trial of former President Joseph Estrada, while Davide and Azcuna were members of the 1986 Constitutional Commission that drafted the 1987 Constitution.

What are amici curiae?

An amicus curiae is a person who is not a party to a case but is invited to provide expert legal guidance on an issue before a court or tribunal.

The concept is recognized in Philippine legal practice. The Supreme Court’s internal rules allow the Court to invite an amicus curiae when necessary, while the Code of Professional Responsibility and Accountability provides that a lawyer generally should not decline, without just cause, a request to serve as an amicus curiae on a matter within the lawyer’s expertise.

The former justices are therefore not part of either the prosecution or defense. Their role is to provide independent legal views that senator-judges may consider in resolving the constitutional issue.

Why are they appearing in VP Sara’s trial?

The issue arose after Senator-Judge Erwin Tulfo questioned Presiding Officer Francis Escudero’s earlier ruling that 16 votes – two-thirds of the full 24-member Senate – are required to convict an impeached official.

Tulfo sought clarification on whether senators who are unable to participate in the trial should still be included in the base used to calculate the constitutionally required two-thirds vote.

Article XI, Section 3(6) of the 1987 Constitution provides that no person may be convicted in an impeachment trial without the concurrence of two-thirds of all the members of the Senate.

The dispute has become significant because several senators have been unable to regularly participate in the proceedings, raising the question of how the phrase “all the Members of the Senate” should apply under the current circumstances.

The amici curiae are expected to address the meaning of that constitutional provision and related questions surrounding the voting base.

The Senate impeachment court is also scheduled to hear oral arguments from the prosecution and defense on September 23 before deciding Tulfo’s challenge to the existing 16-vote threshold.