House prosecution panel member Chel Diokno on Monday expressed confidence that the impeachment case against Vice President Sara Duterte is strong enough to secure a conviction even if the controversial evidence box remains unopened.

Speaking in a radio interview on DZRH, Diokno said the prosecution is prepared to proceed with the trial regardless of the impeachment court's ruling on a pending motion seeking to open and mark the contents of the box.

"Yes, we are ready," Diokno said when asked whether the prosecution has sufficient evidence even without the box. "Of course, we would not file a case unless we were confident that we could prove it."

The so-called "mystery box" has drawn public attention since the impeachment proceedings began in the House of Representatives. Diokno, however, downplayed its significance, saying it is only one piece of the evidence available to prosecutors.

"If we look at where that box came from, it originated from the Bureau of Internal Revenue while the impeachment complaint was still before the House Committee on Justice," he said.

"If that box is not opened, there are other ways to prove what it contains."

Diokno declined to discuss the pending motion involving the box, saying the matter is now before the impeachment court.

"It is now in the hands of the impeachment court, and we will simply abide by whatever decision it makes," he said.

The lawyer also shed light on the pre-trial process, explaining that discussions are currently being supervised by the clerk of court rather than the impeachment court itself.

According to Diokno, the clerk of court merely documents the positions of both parties and submits them to the impeachment court for resolution.

"The clerk of court has no authority to decide issues where both parties disagree," he said. "The matters raised during the pre-trial conference are reported to the impeachment court, and any unresolved issues will likely be addressed when the court reconvenes on July 6."

Diokno said both the prosecution and defense have already submitted their respective witness lists and documentary evidence as part of their pre-trial briefs, allowing each side to prepare for trial.

He also emphasized that both parties have the right to cross-examine each other's witnesses.

"It is not really about objecting to witnesses," he said. "Both panels have the right to cross-examine. We can also cross-examine their witnesses."

Asked whether the prosecution could still present surprise witnesses similar to those seen during the impeachment trial of former President Joseph Estrada, Diokno said Senate rules allow additional witnesses under exceptional circumstances, subject to the impeachment court's approval.

He, however, rejected the idea of intentionally withholding witnesses from the defense.

"That would eventually be discovered," Diokno said. "Neither side is allowed to do that."

Diokno likewise declined to reveal the prosecution's litigation strategy, saying doing so would compromise the case.

"I don't want to disclose our strategy and tactics," he said.

Instead, he said the prosecution's focus is on ensuring that the impeachment proceedings remain understandable to the public.

"One of the challenges in an impeachment case is making sure that people understand what is happening," Diokno said. "It should not be filled only with legal jargon. It has to be something that everyone can understand."

As for the duration of the trial, Diokno said it remains uncertain and will ultimately depend on how much time the impeachment court allocates to both the prosecution and the defense.

"If we base it on the pre-trial briefs, it could take several months," he said. "But that will become clearer once the impeachment court convenes and decides how many trial dates will be given to each side to present their evidence."