The Office of the Ombudsman on Tuesday said its decision to turn former Department of Public Works and Highways (DPWH) Secretary Manuel Bonoan into a state witness was intended to strengthen its case against former House Speaker Martin Romualdez, whom it has identified as one of the alleged masterminds in the flood control scandal.

The explanation came after questions were raised over the dismissal of plunder and graft charges against Bonoan, with some lawmakers arguing that his cooperation should lead to the prosecution of the alleged "big fish" behind the scheme.

Assistant Ombudsman Mico Clavano said Bonoan's firsthand knowledge of the alleged corruption made him a critical witness.

"You cannot penetrate corruption from the outside. You need to have someone on the inside. It was a tough decision for the office to arrive at that, to accept former Secretary Manny Bonoan as a state witness," Clavano said during a press briefing.

Clavano said corruption schemes of this scale rarely leave documentary evidence, making insider testimony essential.

"There will be no document trail. When you talk about corruption, in this magnitude especially, there is no paper trail. That's why the role of Secretary Bonoan is important," he said.

He added that Bonoan was in a position to provide direct information on how the alleged commissions and budget insertions were carried out because he was "in the room" when the scheme allegedly unfolded.

Clavano also said Bonoan's advanced age and deteriorating health were among the factors considered by the Ombudsman.

"We would rather use him as a piece in a case that could change the history of the Philippines than have him convicted of plunder and spend the rest of his days in jail," he said.

Initially refused cooperation

Clavano disclosed that Bonoan initially refused the Ombudsman's request to become a state witness.

According to him, the former public works secretary's refusal prompted prosecutors to file criminal charges against him before the Sandiganbayan.

Only after the filing of the case did Bonoan decide to cooperate with investigators, Clavano said.

Despite the Ombudsman's decision to seek Bonoan's discharge as an accused, Clavano stressed that the final decision rests with the Sandiganbayan, which must approve the motion to amend the case information.

He added that Bonoan's testimony could also be used in other flood control-related cases, including the ongoing plunder case involving former Sen. Bong Revilla.

Bonoan remains confined at the PNP General Hospital while awaiting the Sandiganbayan Fifth Division's ruling on the Ombudsman's motion.