Investigation and the gathering of more evidence against former president Rodrigo Duterte’s bloody drug war are still underway until the confirmation of the charges on 23 September, an ICC-accredited lawyer said Tuesday.

Atty. Joel Butuyan, one of the legal counsels of the drug war victims, is not ruling out the possibility that the prosecutors are still collecting additional pieces of evidence from key witnesses, which reportedly may include police officers, to present a solid case against Duterte in the pre-trial stage in September.

This followed allegations made by Senator Ronald “Bato” dela Rosa that retired cops are being coerced to sign affidavits to implicate him and his former boss, Duterte, by the ICC probers in the notorious anti-drug campaign, which saw thousands of Filipinos killed.

“I do not discount the fact that they may still be interviewing witnesses, although I have no personal knowledge at all whether they are doing that,” said Butuyan in an interview, referring to ICC prosecutors. “The OTP (Office of the Prosecutor) conducts its proceedings confidentially and without any notice to other parties. So the gathering of such evidence can happen.”

The criminal offense outlined in the arrest warrant against Duterte only pertains to murder, equivalent to a single charge. However, this could be amended to include other offenses such as torture and rape if the prosecution is able to produce an additional set of evidence to substantiate it.

“In fact, they can still file additional charges in addition to the crime against humanity of murder that has been sustained in the application for a warrant of arrest. They can expand it and include torture, illegal detention, rape and other forms of sexual violence,” Butuyan averred.

Article 7 of the Rome Statute—the treaty that established the ICC—outlines the criminal offenses that constitute crimes against humanity. This includes murder, torture, rape, enforced disappearance of persons, and other inhumane acts intentionally causing great suffering, or serious injury to the body, among others.

Earlier, Butuyan claimed that new evidence could not only strengthen the case but could also lead to the possible filing of separate charges.

The ICC had granted the prosecutors’ request to extend until 1 July the submission of key evidence against Duterte, as well as applications to keep witness identities confidential until 16 July. The extension is meant to help ensure the safety of the witnesses before their identities are made public.

ICC assistant to counsel Kristina Conti had claimed that law enforcers, such as police officers, may stand as “insider witnesses” against Duterte, noting that this is a usual practice within the international tribunal.

“We’re expecting a few law enforcement officers. I can’t say if they are in active duty still or retired, resigned, but certainly the ICC has not presented any case without insider witnesses. So we’re pretty sure they have already talked to some,” Conti, also a lawyer of the drug war victims, previously said.

“They could be considered as ‘insider witnesses’ where they could talk about the pattern, instructions, and any actions taken before and after the incident,” she added.

De la Rosa, who spearheaded the brutal anti-narcotics crackdown, vowed to launch a congressional investigation into reports that retired police officers are being pressured to testify against him and Duterte—a similar accusation he threw against Speaker Martin Romualdez and Ako Bicol Rep. Zaldy Co in August last year.

De la Rosa served as PNP chief from 2016 to mid-2018. He was succeeded by retired police chief Oscar Albayalde, who continued to oversee the drug war, which saw more than 6,000 deaths, though rights watchdogs estimate that the actual death toll could exceed 30,000—most of them from low-income communities.

Speculations have suggested that De la Rosa and Albayalde could be the next targets of the ICC, as they are allegedly being tagged as “co-perpetrators” of their ex-boss, Duterte.