MALACAÑANG on Thursday challenged Vice-President (VP) Sara Duterte-Carpio’s camp to present evidence supporting its claim that an alleged plot dubbed “Oplan Romanov” existed, which her camp cited to justify the Vice-President’s statement against President Ferdinand R. Marcos, Jr.

At a Palace briefing, Palace Press Officer Clarissa A. Castro said it was up to Ms. Duterte’s camp to substantiate the allegation because they raised the supposed operation before the Senate impeachment court.

She said the Executive branch could not investigate an allegation without supporting information from those making the claim. According to Ms. Castro, the National Bureau of Investigation (NBI) had previously sent a letter to Ms. Duterte seeking details about the alleged threats against her and her family, but she allegedly did not respond.

“It is no one’s fault if there is no evidence of the existence of the so-called Oplan Romanov, because the Vice-President herself, who made the claim, has not proven it,” Ms. Castro said in Filipino.

During Wednesday’s impeachment proceedings, defense lawyer Mark C. Vinluan argued that Ms. Duterte’s remarks were made not in her capacity as Vice-President but as a wife, mother, daughter and sister who believed her family faced real threats under “Operation Romanov.”

Ms. Castro rejected the argument that the alleged operation justified the Vice-President’s statements, saying public office did not exempt anyone from accountability.

“A threat is a threat, no matter who you are,” she said, adding that threatening the President could not be justified by one’s personal circumstances.

The alleged “Oplan Romanov” has figured in the impeachment trial after the defense cited it to explain Ms. Duterte’s remarks last year that she had instructed someone to kill Mr. Marcos, First Lady Maria Louise Araneta-Marcos, and former House Speaker Martin G. Romualdez should she herself be killed.

Prosecutors have argued those statements constituted grave threats, a claim the defense disputes.

Separately, the House prosecution on Thursday defended the testimony of witness NBI senior agent John Mark Sta. Ana Calilung, saying he had properly authenticated a video recording presented during the trial.

San Juan Rep. and House prosecutor Ysabel Maria J. Zamora said that Mr. Calilung’s testimony was intended to establish the authenticity of the video before it could be formally presented before the impeachment court.

“In relation to John Mark Calilung is that he was presented to authenticate the video recording which he made,” Ms. Zamora told a briefing, noting he proved the recording met the required standards and that the NBI agent was qualified to authenticate the video and execute the affidavit.

“We are very happy with the testimony of John Mark Calilung,” Ms. Zamora said.

Meanwhile, House prosecutor Benjamin S. Tolosa, Jr. said that the reported visit of Ms. Duterte’s Chief of Staff Zuleika T. Lopez to the Senate would not affect the case, adding that it still intends to present Ms. Lopez as one of its witnesses in the impeachment trial.

He added that the prosecution has already asked the impeachment court to subpoena Ms. Lopez as a witness and that its plans to present her remained unchanged.

Also on Thursday, a progressive alliance urged the Senate impeachment court to allow only senator-judges who fully participate in Ms. Duterte’s trial to vote on the verdict, saying any move allowing absent senators to do so would undermine the proceedings’ fairness and credibility.

In a statement, Bagong Alyansang Makabayan raised concern over the possibility that Senators Jose “Jinggoy” P. Ejercito Estrada, Jr., Rodante D. Marcoleta and Ronald “Bato” M. dela Rosa could still vote on the verdict despite not fully participating in the trial, while conviction would still require at least 16 votes from senator-judges.

Senate impeachment court presiding officer Francis “Chiz” G. Escudero has maintained that conviction would require at least two-thirds, or 16 votes, of the senator-judges.

Mr. Estrada is detained on non-bailable plunder charges linked to an alleged flood control anomaly, while Mr. Marcoleta remains under medical observation at the Philippine National Police General Hospital pending his transfer to jail after his arrest on a separate non-bailable plunder charge. Mr. dela Rosa, meanwhile, remains at large following an International Criminal Court arrest warrant over alleged crimes against humanity linked to the Duterte administration’s war on drugs. — Erika Mae P. Sinaking, Pexcel John Bacon and Mark Joseph M. Sanchez