House private prosecutor Atty. Jay Tolosa said the testimony of Office of the Vice President Chief of Staff Atty. Zuleika Lopez will be crucial in the impeachment trial of Vice President Sara Duterte because she was present when the alleged verbal threats were made.

Speaking before Monday's trial, Tolosa said Lopez was in the same room when Duterte made the statements that form part of Article IV of the Articles of Impeachment.

"The defense itself pointed out portions of the video showing Atty. Zuleika. She was there when these utterances were made," Tolosa said.

The prosecution's evidence includes video footage presented by National Bureau of Investigation official John Mark Calilung, which contains Duterte's statements regarding an alleged assassin targeting President Ferdinand Marcos Jr., First Lady Liza Araneta-Marcos and former House Speaker Martin Romualdez.

During cross-examination, defense counsel Atty. Joaquin Narvasa argued that Duterte's statements were conditional and made in the context of what the defense described as the House's oppressive treatment of the Vice President and her staff.

The defense also cited Lopez's detention by the House after she was cited in contempt during the investigation into the Office of the Vice President's confidential funds.

Lopez is scheduled to testify for the prosecution on Tuesday, 14 July.