Three amici curiaes Retired Supreme Court Chief Justices Artemio Panganiban and Reynato Puno, along with retired Associate Justice Adolfo Azcuna, attend the impeachment trial of Vice President Sara Duterte at the Senate in Pasay City on Wednesdday, September 16, 2026. Amici curiae, or “friends of the court,” will be providing legal guidance on the constitutional voting requirement for conviction
Aram Lascano
A conviction in an impeachment case could be annulled if political forces deliberately prevent senator-judges from participating and thereby deprive the respondent of a fair and constitutionally proper trial, retired Chief Justice Reynato Puno told the Senate impeachment court Wednesday.
Puno said such a scenario would amount to a violation of the respondent’s right to be judged by the proper number of qualified, fair and impartial judges, potentially rendering the entire proceeding and the resulting conviction null and void.
“If that is really happening and if that can be proven, the result would be the annulment of all the proceedings that were done here,” Puno said.
He said the constitutional problem would not simply concern the number of votes needed to convict but the respondent’s due-process rights.
“The decision will be rendered null and void,” Puno said. “The conviction will also be annulled because the conviction violated the due process clause of the Constitution.”
Puno was responding to a hypothetical raised by Vice President Sara Duterte’s defense over the disputed computation of the two-thirds vote required to convict her.
The defense asked whether allowing the threshold to change based on which senator-judges are able to participate could create an opening for a ruling political faction to deliberately prevent senators from attending the trial — through detention, criminal cases or denial of bail — and thereby alter the number of votes needed for conviction.
The question comes as the Senate impeachment court considers whether the constitutional phrase “two-thirds of all the Members of the Senate” means the full 24-member chamber even when some senator-judges are unable to participate.
He said the respondent has a right to be judged by judges who are “fair and impartial” and by the “right number” of qualified judges.
If those safeguards are violated, Puno said, the resulting conviction would not stand.
“Ganyan din po ang mangyayari dito. If all those safeguards are violated, the result is annulment of the proceedings, dismissal of the decision of conviction,” he said, referring to an impeachment proceeding in which the constitutional safeguards for the respondent were violated.
Azcuna, meanwhile, argued Wednesday that keeping the entire Senate membership as the denominator provides a safeguard against political manipulation.
“There is no guarantee. That is the danger that was seen by the drafters of our Constitution,” Azcuna said when asked whether changing the constitutional voting base could allow a president, official or political allies to remain in power and suppress political opponents.
Azcuna warned that basing the threshold on actual attendance could allow whoever controls the ability of senators to participate to influence the number of votes required for conviction.
“It can still be manipulated, but it's not as easy if you leave it to the mere presence as a denominator,” he said.
Senators Jinggoy Estrada and Rodante Marcoleta, both Duterte allies, are detained in connection with separate criminal cases. Another ally, Sen. Ronald “Bato” dela Rosa, has also been unable to participate regularly amid proceedings involving an International Criminal Court warrant related to the drug-war case against former President Rodrigo Duterte.
Duterte and her allies have characterized the cases and other actions against them as political persecution, accusing the Marcos administration of targeting political opponents.
