THE Senate impeachment court on Thursday named retired chief and associate justices of the Supreme Court as amici curiae, or “friends of the court,” to help the court resolve the disputed voting threshold for convicting Vice President Sara Duterte.
Impeachment court spokesman Reginald Tongol said former Chief Justices Artemio Panganiban and Reynato Puno, and retired Associate Justice Adolfo Azcuna will appear before the court on Sept. 16 to give their legal opinions.
Additionally, former Chief Justice Hilario Davide Jr., who presided over former president Joseph Estrada’s impeachment trial, will submit a written legal memorandum, Tongol said.
“The impeachment court reserves its plenary prerogative to invite additional experts should the situation demand it — so this four-man roster constitutes the court’s list of amici curiae thus far,” Tongol said in a statement.
“The impeachment court commends the prompt cooperation of these distinguished jurists. Securing their counsel marks a critical procedural milestone, ensuring that this trial proceeds anchored on verified constitutional bedrock,” he added.
As to the written advisories that they may submit beforehand, Tongol said the senator-judges will hold the right of first review.
Hence, he said the impeachment court will not release or comment on the substantive details of any amicus advisory before their formal presentation.
“The Senate impeachment court maintains the highest level of procedural discipline over the upcoming Sept. 16, 2026 presentation. Floor time will be strictly controlled by the presiding officer,” Tongol said.
He said the live panel of amici curiae will present their advisories, Davide’s memorandum will be formally entered into the record, and the microphones will open exclusively for the senator-judges to ask clarificatory questions.
“Since an amicus curiae provides expert legal doctrine, not factual evidence and the constitutional right to cross-examine applies only to fact witnesses, not scholars advising the bench, the legal panels will just sit and listen during the whole presentation,” he added.
After hearing the experts, Tongol said the prosecution and defense will be given 15 minutes each for oral arguments on Sept. 23.
He said the senator-judges will then vote on Senator-Judge Erwin Tulfo’s appeal questioning Presiding Officer Francis Escudero’s ruling on the first day of the trial in July, setting the conviction threshold at 16 votes based on the full 24-member Senate.
“The impeachment court will not rush the resolution of this constitutional threshold. Doctrinal accuracy and constitutional exactitude take precedence over speed,” Tongol said.
In his manifestation, Tulfo questioned whether the constitutional phrasing “all members” strictly means 24, regardless of the absence of four lawmakers who are beyond the Senate’s coercive jurisdiction.
Tulfo pointed out that the chamber relies on the 1949 Supreme Court ruling Avelino v. Cuenco in determining a legislative quorum, which calculates the majority based only on members physically capable of attending.
“If we insist that the voting base is fixed at 24, regardless of the evidence presented, regardless of the vote of the senators who are able to listen to the testimonies, the absence of those senators, whether we like it or not, will result in an acquittal by default,” he said.
Article XI, Section 3(6) of the 1987 Constitution provides that an impeached official cannot be convicted “without the concurrence of two-thirds of all the members of the Senate.” Four senators are currently unable to attend the trial: Sen. Ronald dela Rosa, who is in hiding because he faces an arrest warrant from the International Criminal Court; Senators Jinggoy Estrada and Rodante Marcoleta, who are detained on the non-bailable charge of plunder before the Sandiganbayan; and Sen. Loren Legarda, who is abroad on an extended medical leave.
