MANILA, Philippines — The prosecution presented its first witness at the Senate Impeachment Court on Tuesday who will authenticate a video that contained the alleged threat of Vice President Sara Duterte against President Ferdinand Marcos Jr., first lady Liza Araneta-Marcos and then speaker Martin Romualdez.

National Bureau of Investigation (NBI) senior agent John Mark Calilung, assigned with the cybercrime investigation unit, was called to testify on the authenticity of the video, one of the pieces of evidence on the charge of grave threat contained in the fourth Article of Impeachment filed against Duterte.

In his opening statement, Private prosecutor Amando Virgil Ligutan said that the evidence were not just derived from testimonies or authenticated documents, but also from Duterte's own words and own admissons.

"An official who under the constitution stands to succeed the president of the Republic such statement carry a gravity far from the exercise of one's freedom of expression, they strike at the very heart of government," Ligutan said.

"This is especially significant given that she has publicly declared her intention to run for president in the next election," he added.