Explainer: Mass graves in Gaza: what do we know?

The discovery of mass graves at two Gaza hospitals, said by Palestinian authorities to contain hundreds of bodies, have triggered calls by the UN rights chief and others for an international investigation.

While not defined under international law, a mass grave is a burial site containing multiple bodies, the existence of which could be important in detecting possible war crimes.

What is known about mass graves discovered in Gaza?

Palestinian authorities said a grave site discovered at the Nasser hospital, the main medical facility in central Gaza, contained nearly 400 bodies. It was uncovered after Israeli troops pulled out of the city of Khan Younis.

Reuters reporters on Monday saw emergency workers digging corpses out of the ground in the ruins of Nasser hospital.

Another gravesite was also found by Palestinian authorities at the Al Shifa hospital in northern Gaza, which had been targeted by an Israeli special forces operation. Reuters has verified footage of the digging of graves near the hospital since November.

United Nations spokesperson Ravina Shamdasani said on Tuesday an investigation was needed to verify the number of bodies, but that "clearly there have been multiple bodies discovered."

"Some of them had their hands tied, which of course indicates serious violations of international human rights law and international humanitarian law, and these need to be subjected to further investigations," Shamdasani said, speaking on behalf of the UN High Commissioner for Human Rights Volker Turk.

Is there an investigation?

The International Criminal Court in The Hague has an active investigation into the October 7 attack.

The office of the prosecutor has jurisdiction in the Palestinian territories but has not made any public comments about the discovery of mass graves.

Where else have mass graves been discovered?

Recent examples include the conflicts in Sudan and Ukraine.

Kyiv says more than 1,400 people were killed in the town of Bucha while it was occupied by Russian forces following Moscow's full-scale invasion on Feb. 24, 2022, with more than 175 of the victims discovered in mass graves.

Marking two years since the events in Bucha, Ukrainian Prosecutor General Prosecutor General Andriy Kostin said this month that the killings "bear hallmarks of genocide".

In Sudan's West Darfur, at least 1,000 bodies were buried in Al Ghabat cemetery during weeks of massacres in the city of El Geneina between April and June last year.

Is it illegal to disturb a mass grave?

Under the 1949 Geneva Conventions, to which Israel is a signatory, parties to a conflict must take all possible measures to prevent the dead from "being despoiled".

Customary international humanitarian law (IHL) calls for the dead to be respected, including a duty to prevent despoiling of graves and ensuring the identification and proper burial of human remains.

IHL also prohibits mutilation, desecration and other forms of disrespect towards the dead, while parties should take measures to protect grave sites, including those containing multiple human remains.

In 2002, in a case related to killings of Palestinians in the Jenin refugee camp in the West Bank, Israel's Supreme Court ruled that the Israeli Defence Ministry was responsible under international law "for the location, identification, evacuation, and burial of the bodies" of Palestinians killed in fighting. The judges said bodies should not be buried in mass graves but handed over to the Palestinian authorities.

The International Criminal Court's founding Rome Statute defines the desecration or mutilation of dead bodies as a war crime and this is banned as an outrage upon personal dignity.

Allegations by Palestinian authorities that the Israeli Defence Forces (IDF) had buried the bodies were "baseless and unfounded," the IDF said in a statement. The graves were dug by Palestinians, it said, releasing footage showing the graves pre-dated IDF operations.

IDF forces searching for Israeli hostages had examined bodies buried near Nasser hospital and then returned them, the IDF said. "The examination was carried out respectfully while maintaining the dignity of the deceased," it said.

Have mass graves been important in past war crimes trials?

Evidence from mass grave exhumations played a crucial role in trials at the U.N. International Criminal Tribunal for the former Yugoslavia (ICTY) that established the 1995 Srebrenica massacre of some 8,000 Muslim men and boys by Bosnian Serb forces was a genocide.

In the trial of Bosnian Serb general Radislav Krstic, the first person to be convicted on genocide charges by the Yugoslav tribunal in 2001, judges found that evidence from exhumations showing hundreds of victims were buried with blindfolds and had their hands likely tied behind their backs was enough to conclude they had not been killed in combat.

"Mass graves contain critical evidence for establishing the truth about events that have taken place," the International Commission on Missing Persons said in a statement about Gaza on Wednesday. "Immediate measures must be taken to protect and document locations where mass graves have been reported in Gaza."

The Hague-based ICMP, which helped identify thousands of victims buried in mass graves during in the Balkan wars in the 1990s, said that in the event that war crimes occurred "these processes make it possible to bring perpetrators to justice".

What are the consequences of violating laws on mass graves?

If the reburial or opening of mass graves led to desecration of human remains, charges could be brought by the ICC. Reports of attempting to cover up crimes by putting people in mass graves could also be used in court as evidence to support that the perpetrators knew the killings were unlawful.

Confirmed cases of people being killed while they had their hands tied behind their backs could be used by judges to conclude that those killed were not active combatants. Under the ICC statute it is a war crime to kill or wound a combatant in custody.