In Historic First, 4 Ex-Supreme Court Justices Sit as Amici Curiae in Impeachment Court

MANILA, Philippines — The Senate Impeachment Court paused its trial schedule on 16 September 2026 to hold a session for legal advice. Four legal experts—three former Chief Justices and one retired Associate Justice of the Supreme Court—were called to address a key constitutional question: whether the rule that no official be convicted without "two-thirds of all the Members of the Senate" keeps the required vote fixed at 16 out of 24, or whether that number changes when sitting lawmakers cannot participate.

The panel comprised three former chief justices—Hilario Davide Jr., Artemio Panganiban, and Reynato Puno—alongside retired Associate Justice Adolf Azcuna. All four jurists brought extensive judicial experience, with Davide and Azcuna having also served as framers of the 1987 Constitution. With four sitting senators unable to take part in the proceedings, their testimonies revealed a clear divide between flexible constitutional interpretation and strict adherence to the text.

Former Chief Justice Hilario Davide Jr., a principal framer of the 1987 Constitution who presided over the historic impeachment trial of former President Joseph Estrada and served as top magistrate from 1998 to 2005, submitted a detailed legal memorandum asserting that "all members" must be computed exclusively from senators who are living, qualified, and active. Davide argued that the framers assumed the word applied strictly to functional legislators, emphasizing that lawmakers who are untraceable, bedridden, or stripped of their authority should be omitted from the denominator. He noted that the calculation should centre on "the number of senators who are qualified to vote" rather than blindly applying a blanket number.

Former Chief Justice Artemio Panganiban, who led the judiciary from 2005 to 2006, echoed this pragmatic stance, stressing that real-world conditions supersede abstract math.

"24 multiplied by two-thirds is always 16 in the abstract," Panganiban stated. "But not always in reality. Reality sometimes, Your Honors, changes the denominator in mathematics."

Emphasising the court’s sole responsibility to resolve the question, he directly addressed the bench: "You are called upon by our people to decide impeachment cases. Then decide it from where you sit. Only when you commit grave abuse of discretion should your decision be set aside."

When Senator-judge Panfilo Lacson raised a scenario regarding nine senators stranded abroad, leaving only 15 to sit in judgment, Panganiban responded that consulting amici curiae protects the court from allegations of arbitrary action: "You are holding this meeting so that you cannot be accused of grave abuse of discretion should that time come." He added that "fairness can still be rendered with two-thirds of the remaining 15."

Senator-judge Joel Villanueva asked how the tribunal should view absent or impaired colleagues, to which Panganiban stressed the necessity of direct engagement: "Trial courts rely on firsthand observations of witnesses to find the truth. Meaningful adjudication requires active participation."

Elaborating on this flexible doctrine, former Chief Justice Reynato Puno, who presided over the high court from 2007 to 2010 and is celebrated for his progressive constitutionalism, cautioned the court against a rigid literalism, noting: "The Senate impeachment court is not under the Supreme Court and has the sole power to try and decide all cases of impeachment."

During his interpellation, Senator-judge Joel Villanueva pressed Puno on how the court ought to handle colleagues facing legal impediments or detention:

Senator-judge Joel Villanueva: "How should the court address the status of senators currently under detention or facing legal impediments to sit as judges?"

Former Chief Justice Reynato Puno: "Dito po sa sitwasyon halimbawa na ito, kung sila ay ire-release, they will be released not because they are accused but because they will perform their duties as judges. They can perform their duties as judges na hindi naman kailangan pumunta dito sa Senado... Puwede silang bigyan ng whatever devices, laptop. They can see the witnesses testifying. They can be provided with transcripts."

Senator-judge Erwin Tulfo followed up on whether the tribunal’s decision on the threshold can be challenged externally:

Senator-judge Erwin Tulfo: "Does the impeachment court hold the ultimate authority to interpret the two-thirds rule without judicial interference?"

Former Chief Justice Reynato Puno: "The tribunal answers directly to the Constitution rather than external oversight. The Senate, when sitting as an impeachment court, exercises exclusive constitutional jurisdiction."

Standing as the sole dissenter among the experts, retired Associate Justice Adolf Azcuna—a former magistrate from 2002 to 2009 and veteran delegate of the 1986 Constitutional Commission—delivered a firm counter-argument, maintaining that the baseline cannot shift.

"I respectfully submit, Your Honors, that the reference in this provision is to all members. As long as they are members of the Senate, they constitute the denominator in computing the threshold of two-thirds, because all means all," Azcuna testified. "Basing the denominator on only those who actually participate and are present can effectively reduce the two-thirds to a simple majority."

Senator-judge Joel Villanueva engaged Azcuna directly on whether absent members should be counted in the baseline:

Senator-judge Joel Villanueva: "Should absent or incapacitated members still be factored into the overall math when computing the required vote?"

Former Associate Justice Adolf Azcuna: "We have to make a distinction between the right to vote in the impeachment proceedings and the inclusion of that person in computing the two-thirds. As long as he is a member of the Senate, he has to be included in the two-thirds denominator. The only exception is if he dies, if he is removed from office, or if he resigns. No more."

Following the session, public prosecutor Rep. Keith Flores addressed the prosecution's stance during a press briefing, emphasizing that the panel remains focused on presenting evidence regardless of where the Senate sets the final voting baseline: "For us, we will stick to the principle that we would just sink or swim with the evidence that we'll be presenting before the impeachment court."

Earlier, before the presentation of the legal experts began, defense counsel Michael Poa entered a manifestation ad cautelam (filed "out of caution" or "for safety's sake"—a legal precaution taken to reserve rights without waiving objections or recognizing authority) on behalf of Vice President Sara Duterte. The filing clarified that the defense team's participation in the discussions was without prejudice to their position that the Senate cannot alter the constitutional threshold, explicitly reserving the right to seek legal remedies before the Supreme Court should the ruling go against them.

As Presiding Officer Francis "Chiz" Escudero and the senator-judges evaluate these arguments, the impeachment court faces a historical choice between holding fast to a fixed 16-vote requirement or lowering the threshold before the trial moves to its final verdict.