Former National Bureau of Investigation (NBI) Director Jaime Santiago on Wednesday defended the bureau's investigation into Vice President Sara Duterte's controversial remarks and criticized the defense panel's cross-examination during her impeachment trial as repetitive.

Speaking in a DZRH interview, Santiago said defense lawyer Mark Vinluan repeatedly questioned current NBI Director Melvin Matibag about matters that had already been clarified during Tuesday's proceedings.

"I couldn't help [but laugh] at the cross-examiner because he kept going back to the subpoena. The director had already said several times that he was not yet the director at that time," Santiago said in Filipino.

He also criticized repeated questions about documents Matibag did not sign because he had not yet assumed office.

"They kept asking, 'You didn't sign this? Did you sign this?'"

Santiago however said lawyers were simply doing their job but urged them to exercise "common sense."

"If I were still a judge and that was the kind of cross-examination taking place, I would bang the gavel on his head."

"We understand that it's their job, but we also need to have a little common sense so we don't end up looking foolish before the public," he added.

Matibag testified Tuesday on the NBI's investigation into Duterte's November 2024 remarks that she had spoken to someone about killing President Ferdinand Marcos Jr., First Lady Liza Araneta-Marcos and former House Speaker Martin Romualdez if she were killed.

No invitation

Santiago, who served as NBI director from June 2024 to August 2025 — when Vice President Sara Duterte made the remarks — said the House prosecution panel did not invite him to testify.

"I did not receive any invitation from the prosecution. But I read in a news [report] that Vice President Sara included me as one of her witnesses."

'Matter of national security'

Asked whether he agreed with Matibag's assessment that Duterte's remarks constituted grave threats and a national security concern, Santiago said the NBI was merely fulfilling its mandate.

"Whenever there are threats against high-ranking officials — from the President, Vice President, Speaker of the House, Senate President down to the Chief Justice — the NBI has jurisdiction. That is our mandate."

He added that the remarks could influence Duterte's supporters.

"I agree with Director Matibag. Based on the utterances of Baste and Vice President Sara, there are people who believe in them and will listen to what they say. So this is not only a threat to the President; our national security could also be affected."

Probe into threats vs. Duterte

Santiago also rejected claims that the NBI ignored alleged death threats against Duterte, saying investigators repeatedly invited her to cooperate.

"She did not appear. We invited her twice, but only her lawyer came and submitted a letter. The first time, she said she was busy. The second time, she no longer wanted to come."

He also addressed "Operation Romanov," saying the term originated from remarks made by Davao City Mayor Sebastian "Baste" Duterte.

"It started with Mayor Baste. He said during a press conference, 'Before you go to bed, remember Romanov... Mussolini, remember what happened to your family in 1986.' So 'Operation Romanov' came from Baste."

Santiago said he did not consider the "Romanov" remarks a threat against the vice president.

A licensed criminologist and graduate of the Philippine College of Criminology, Santiago said he has returned to teaching at the Universidad de Manila following the end of his term as NBI director.