The Office of the Ombudsman on Tuesday defended its decision to turn former Public Works Secretary Manuel Bonoan into a state witness, saying the move is aimed at strengthening its case against former House speaker Martin Romualdez whom investigators have tagged as one of the alleged masterminds of the multibillion-peso flood control corruption scandal.

Assistant Ombudsman Mico Clavano said Bonoan’s cooperation was crucial because corruption cases of this scale rarely leave a documentary trail.

“You cannot penetrate corruption from the outside. You need someone on the inside. It was a tough decision for the office to accept former secretary Manny Bonoan as a state witness,” Clavano said in a press briefing.

Clavano said Bonoan could provide critical details on how the alleged scheme operated, particularly discussions on commissions and percentages allegedly received by the lawmakers involved.

“When you talk about corruption of this magnitude, there is usually no paper trail. That is why secretary Bonoan’s role is important because he was in the room when these things were happening,” he said.

The Ombudsman earlier dropped the plunder and graft charges against Bonoan as part of efforts to secure his testimony, a move that drew questions from lawmakers who argued that the bigger figures involved in the scandal should be prosecuted.

Clavano revealed that Bonoan initially refused to cooperate, prompting the Ombudsman to first file criminal charges against him before he eventually agreed to become a witness. However, he said Bonoan’s immunity would still depend on whether the Sandiganbayan will approve the Ombudsman’s motion to amend the case information.

Apart from his testimony against Romualdez, prosecutors said Bonoan is also expected to testify in other flood control-related cases, including the ongoing malversation trial of former senator Ramon “Bong” Revilla Jr. before the Sandiganbayan. Bonoan is scheduled to take the witness stand on 28 July.

On Monday, Ombudsman Jesus Crispin Remulla confirmed that Bonoan would serve as a state witness in several criminal cases tied to the flood control scandal.

Bonoan had been charged as a co-conspirator of Senator Jinggoy Estrada in the alleged receipt of P573 million in kickbacks from infrastructure projects in 2025.

Remulla said Bonoan’s age and deteriorating health — he remains confined at the PNP General Hospital — were among the factors considered in the decision.

“His health is a concern to us, and we want to preserve his testimony as soon as possible. It is important that he be discharged so he can become our witness,” Remulla said.

The Ombudsman said the strategy is part of efforts to speed up corruption cases and break the pattern of public officials escaping accountability due to years of legal delays, stressing that charges are only filed once sufficient evidence has been established.