Aside from the defense team, the senator judges also questioned an agent from the National Bureau of Investigation (NBI) regarding Vice President Sara Duterte's alleged impeachable offense of grave threats.

According to the witness, the President or any high-ranking government official does not need to personally file a complaint before an investigation can be conducted.

NBI Agent John Mark Calilung, the witness, said his executive officer called him and instructed him to investigate a virtual press conference held by VP Sara on November 23, 2024, due to an alleged statement made against President Ferdinand Marcos, First Lady Liza Marcos, and former House Speaker Martin Romualdez.

He first watched clippings of the alleged threat before watching the full two-hour-long video conference. He reported this to his boss, which triggered a search for video patterns to check if the Vice President had made similar statements against the President.

NBI Agent John Mark Calilung clarified the investigation they conducted against Vice President Sara Duterte, which became the basis for the House of Representatives' fourth article of impeachment — grave threats and inciting to sedition.

In a clarificatory question from Senator Judge Erwin Tulfo, he asked about the NBI's authority to investigate crimes against high-ranking officials, including the President, Vice President, Senate President, House Speaker, and Chief Justice.

According to Calilung, there is no need to request permission from such officials before they can act and conduct a preliminary investigation, and he said the NBI also has the authority to file complaints with the Department of Justice.

John Mark Calilung
Witness / Senior Agent, NBI
"If we found the evidence is enough that there is crime committed, we will file a case because that is the output of our investigation sir."

Senator Judge Erwin Tulfo
"Kahit po ba hindi nagreklamo ang biktima, in this case ang pangulo, biktima ng threat, kahit hindi sya nagreklamo sa inyo, automatic po yun?"

(Even if the victim did not file a complaint — in this case, the President, who is the victim of the threat — even if he did not file a complaint with you, is that automatic?)

John Mark Calilung
Witness / Senior Agent, NBI
"Yes, your honor."

Meanwhile, Senator Judge Allan Peter Cayetano asked whether, under this same system, the NBI also conducted an investigation into the alleged threat against the Vice President — especially since the Vice President's statement in the same video conference came after she was asked about the alleged threat called "Operation Romanov," which allegedly planned to wipe out the Duterte family.

Senator Judge Cayetano pointed out the conditional nature of VP Sara's statement.

However, according to the witness, he still considers it an absolute threat, adding that the National Security Council had earlier issued a statement considering it an active threat.

In questioning from Senator Judge Joel Villanueva, Calilung described how a threat could be considered active in relation to whether it would constitute an impeachable offense for the Vice President.

According to the defense, at the time VP Sara made the alleged threats, she was experiencing systematic oppression, as it coincided with the period when former Chief of Staff Zuleika Lopez was detained by the House of Representatives after being cited in contempt in November 2024.

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