The House prosecution panel on Tuesday presented its first witness in the impeachment trial of Vice President Sara Duterte, with an National Bureau of Investigation (NBI) digital forensics expert testifying that videos containing her alleged threats against top government officials were authentic.

NBI Senior Agent John Mark Calilung, a digital forensics specialist from the bureau's Cybercrime Division, testified that he examined and authenticated Duterte's 23 November 2024 livestream and other video recordings cited in the Articles of Impeachment.

During cross-examination, defense lawyer Amando Virgil Ligutan asked Calilung how he verified the authenticity of the more than two-hour livestream.

Calilung said he used Open Broadcaster Software (OBS), an open-source application commonly used for livestreaming and screen recording, to compare the recorded file with the original broadcast.

Responding to questions from Senator Joel Villanueva, Calilung explained that OBS records everything displayed on a computer screen, allowing investigators to manually compare the captured output with the original livestream to verify its integrity.

Threat videos played

At the prosecution's request, the impeachment court played portions of Duterte's 23 November 2024 livestream after Presiding Officer Francis "Chiz" Escudero approved the motion.

Escudero rejected Senator Alan Peter Cayetano's proposal to play the entire two-hour video, ruling that only portions relevant to the Articles of Impeachment needed to be presented.

"With a caveat that a portion of an entire video being presented is not only to save on time, but also to support the allegations of the prosecution," Escudero said.

Senator Erwin Tulfo likewise said the rules of evidence do not require an entire recording to be played in open court.

The defense objected, arguing that presenting isolated clips stripped Duterte's statements of their full context.

Among the clips shown was Duterte's statement: "Huwag kang mag-alala... kapag pinatay ako, patayin mo si BBM, si Liza Araneta, at si Martin Romualdez."

The court also viewed a separate press conference in which Duterte spoke of "beheading" President Ferdinand Marcos Jr. and told Senator Imee Marcos she would have the remains of former President Ferdinand Marcos Sr. exhumed and thrown into the West Philippine Sea.

Calilung also testified that he authenticated videos showing the reactions of President Marcos and then-House Speaker Martin Romualdez to Duterte's remarks, concluding that the recordings were authentic and had not been tampered with.