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MANILA — A human rights group on Tuesday said it is optimistic the International Criminal Court (ICC) would junk the Philippine government's appeal and allow its prosecutor to proceed with the investigation on former President Rodrigo Duterte's bloody drug war.

This, as victims of Duterte's anti-drug policy await the ICC's decision on the Philippines' appeal expected to be handed down on Tuesday at 4 p.m. Manila time.

• ICC says ruling on PH govt's ICC probe appeal out on July 18

"This decision today, however it goes, is a key moment for the victims of the drug war violence and the Davao Death Squad violence when Duterte was mayor of Davao City," said Carlos Conde, senior researcher of Human Rights Watch.

Conde cited the Philippine government's "opaqueness" in dealing with the public about the drug war violence since 2016, particularly in the official numbers that were provided by the Philippine National Police (PNP) until President Ferdinand Marcos Jr. assumed office last year.

"The fact that the authorities have not been able to provide the media, the public with their own data of how many exactly have been convicted and investigated—out of the thousands of cases—points you to the fact that the Philippine government has been very opaque," he said.

The way the Philippine government has also been treating the ICC—even going so far as denouncing the court and accusing its investigation as being politicized—does not inspire confidence that the international court may grant the Philippines' appeal, Conde added.

"We are very optimistic that the ICC will look at whatever evidence is there, the information that's been filed with them by the families of victims of the drug war—it's this evidence and this information, these testimonies are too important, too massive to ignore... that's why we think that the ICC will rule in favor of the victims of the drug war," he also said.

He also dismissed claims that the ICC investigation was not a "gut issue," as many of the drug war victims were from the Filipino poor.

"A huge majority of them are poor people, so this is a gut issue. A lot of the victims of human rights abuses, a lot of those who have lost their loved ones in the drug war are still reeling from the impact of the violence. This is something that they care deeply about, and we are hoping that the favorable decision from the ICC would give them a measure of justice, a measure of closure, a measure of accountability," Conde added.

The Marcos administration has shunned the ICC probe, with President Marcos himself saying that the court had "no jurisdiction" in the Philippines and its investigation being a "threat to our sovereignty."

"We cannot cooperate with the ICC considering there are very serious questions about their jurisdiction and about what we consider to be interference and practically attacks on the sovereignty of the republic,” Marcos said last March.

• 'Threat to our sovereignty': Marcos won't allow ICC in PH for Duterte drug war probe
• Marcos: PH to 'disengage from any contact' with ICC after rejection of appeal to suspend probe

On Monday, Justice Secretary Jesus Crispin Remulla also said that the Philippines would not implement any arrest warrant, should the ICC issue one, on its drug war probe.