MANILA — Senator-judges are scheduled to vote Wednesday, September 23, on the number of votes required to convict Vice President Sara Duterte as her impeachment trial enters its 29th day.

Before Tuesday’s proceedings were adjourned, presiding officer Sen. Francis “Chiz” Escudero said no witness would be presented Wednesday because the prosecution and defense would instead deliver oral arguments on the disputed voting threshold.

Each side will be given 15 minutes to present its position. Senator-judges may then question the parties before voting on Sen. Erwin Tulfo’s appeal and motion for reconsideration of Escudero’s earlier ruling.

House Lead Prosecutor and Batangas Rep. Gerville Luistro said Mamamayang Liberal Party-list Rep. Leila de Lima will present the prosecution’s arguments.

Lead defense counsel Sheila Sison, meanwhile, had not disclosed as of Tuesday who would argue for Duterte’s defense.

The issue stems from Escudero’s ruling on the first day of the trial on July 6 that 16 votes are required to convict Duterte, based on the constitutional provision stating that no impeached official may be convicted without the concurrence of two-thirds of all members of the Senate.

Tulfo later sought reconsideration of that ruling, questioning whether the two-thirds requirement should be computed from all 24 senators or only from senator-judges able to participate in the trial.

Tulfo has said his motion is not intended to lower the constitutional threshold but to clarify whether senators who cannot participate should still be counted in determining the required number of votes.

The issue has become significant because several senators have not been participating in the proceedings.

Sens. Jinggoy Estrada and Rodante Marcoleta are detained in connection with separate plunder cases, Sen. Ronald “Bato” dela Rosa has been absent amid an International Criminal Court arrest warrant, while Sen. Loren Legarda is on medical leave.

On September 16, the impeachment court heard the positions of four retired Supreme Court magistrates invited as amici curiae, or friends of the court.

Former Chief Justices Hilario Davide Jr., Artemio Panganiban and Reynato Puno said the 16-vote requirement is not necessarily fixed and argued that the computation should take into account which senators are legally qualified or able to participate in deciding the case.

Former Associate Justice Adolfo Azcuna took a different position, saying all sitting senators should remain part of the denominator as long as they continue to be members of the Senate.

Azcuna said only death, resignation or removal from office would reduce the Senate membership used in computing the two-thirds requirement.

The impeachment court is scheduled to resume today, September 23, Wednesday, for the oral arguments before senator-judges consider Tulfo’s motion on the conviction threshold.

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