The 16-vote threshold required to convict Vice President Sara Duterte is expected to remain, with little chance that the Senate impeachment court will lower it in the middle of the trial despite concerns raised by the prosecution over the frequent absences of some senator-judges.

Impeachment court spokesperson Reginald Tongol warned that the prosecution's proposal is “dangerous” because it would require the court to change its rules while proceedings are already underway, which he said is “not allowed.”

“We are not just playing here for the convenience of the parties to change the rules mid-trial,” Tongol told reporters in a virtual briefing. “The impeachment court does not act for the convenience of either the prosecution or the defense. It is acting to uphold the due process requirements under the law.”

Tongol said the ruling of impeachment court presiding officer Chiz Escudero setting the threshold at 16 votes remains “set in stone” unless its legality is challenged before the Supreme Court and overturned.

Another possible route would be for a majority of senator-judges to reverse the ruling, although Tongol said it remains unclear whether the impeachment court would still allow such a challenge.

“No one [challenged it] on July 6. It is now unclear under the rules if that is still [subject to appeal or whether] anytime within the 90 days of trial, it can still be appealed,” he said.

Escudero settled the legal debate over the conviction threshold at the start of the trial on 6 July, maintaining that 16 affirmative votes are required for a guilty verdict regardless of how many senators are present.

The ruling came amid differing interpretations of whether the constitutionally mandated two-thirds vote of the 24-member Senate should still apply when three senators are unable to participate in the trial and are unlikely to cast votes.

The number of active senator-judges has fallen from 24 to 21 following the arrests of Senators Jinggoy Estrada and Rodante Marcoleta on plunder charges. Senator Ronald “Bato” dela Rosa, meanwhile, remains in hiding amid an outstanding warrant from the International Criminal Court.

Senator-judges Alan Cayetano and Loren Legarda have also been absent from the proceedings for three and nine days, respectively.

Legarda has extended her medical leave, which began on 3 August, amid a preliminary investigation by the Office of the Ombudsman.

House prosecution spokesperson and private counsel Benjamin Tolosa Jr. earlier said the frequent absences could prompt the impeachment court to reconsider the threshold.

Tongol, however, expressed reservations, saying Escudero's ruling was anchored on the Supreme Court's 2000 decision in Bayan v. Zamora, which held that the Senate is composed of 24 members.

He also warned that changing the rules during the trial would run counter to the intent of the framers of the Constitution, who deliberately set a high bar for impeachment convictions.

“Because the impeachment court will necessarily cancel the mandate of the people who elected the impeachable officer, that’s why it is made extra hard,” Tongol said.

“Two-thirds is not a simple majority. It was the intention of the framers of the Constitution to make it hard for impeachment to happen,” he added.

Article XI, Section 3(6) of the Constitution provides that no person may be convicted in an impeachment trial without the concurrence of two-thirds of all members of the Senate. With a 24-member Senate, that translates to 16 votes.

A conviction would result in Duterte's removal from office and could include disqualification from holding public office, potentially ending her prospects of seeking the presidency in 2028.

Legal experts remain divided over how the threshold should apply when some senator-judges cannot participate.

Former Supreme Court Associate Justice Adolfo Azcuna earlier told the Daily Tribune that the impeachment court “cannot lower the threshold for conviction unless it expels a member or possibly declares him or her as resigned.”

Azcuna, one of the framers of the 1987 Constitution, added that some legal experts in the Citizens’ Jury believe senators unable to actively participate should not be included in determining the threshold.

Absent senators, however, effectively do not contribute votes toward the 16 required for conviction, he said.