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What are war crimes, and is Russia committing them in Ukraine?

People stand amid newly-made graves at a cemetery in the settlement of Staryi Krym outside the Ukrainian city of Mariupol on May 22. (Alexander Ermochenko/Reuters)
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A court in Kyiv on Monday sentenced a Russian soldier to life in prison for killing an unarmed man, accusing 21-year-old Vandi Shishimarin of premeditated murder and violating the “rules and customs of war.”

The trial was the first prosecution of a Russian service member for war crimes committed in Ukraine since the Feb. 24 invasion. Shishimarin pleaded guilty to shooting Oleksandr Shelipov, 62, in the northeastern Sumy region in the first week of the war.

Ukraine’s prosecutor general, Iryna Venediktova, said Monday that authorities have opened more than 13,000 investigations into suspected war crimes committed by the Russian government and military. Two more soldiers are already on trial for allegedly shelling civilian targets in the region of Kharkiv.

Ukraine is so far prosecuting Russian forces under its own criminal code. But the chief prosecutor of the International Criminal Court at The Hague is also investigating alleged war crimes and crimes against humanity in Ukraine.

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The International Criminal Court said on Feb. 28 it is investigating possible war crimes in Ukraine. Experts tell The Post how the legal process works. (Video: Alexa Juliana Ard/The Washington Post)

Here’s what to know about war crimes and how perpetrators are prosecuted.

What counts as a war crime?

The modern framework for assessing war crimes was born out of the Nuremberg trials following World War II. Nazi Party officials, military officers and German elites were tried on charges including crimes against humanity. At the time, the international community sought to establish guardrails that would minimize the horror of future conflicts.

People often use “war crimes” colloquially to describe a range of actions prohibited under international law during conflict, said William Schabas, a professor of international law at Middlesex University in London. But the term has a precise, technical definition, referring to violations of international law governing conduct in combat and during occupation.

Those violations are spelled out in international treaties such as the Geneva Conventions of 1949 and the Rome Statute, which established the International Criminal Court in 2002 to prosecute individuals responsible for war crimes, along with crimes against humanity and genocide — themselves complex terms with their own set of legal parameters.

War crimes include the deliberate targeting of civilians; attacks that cause disproportionate civilian casualties given the military objective; and attacks on hospitals, schools, historic monuments and other key civilian sites. Plenty of horrific acts of violence resulting in civilian deaths would not meet the definition.

The Rome Statute specifies that intentionally launching an attack that will cause “widespread, long-term and severe damage to the natural environment” could be a crime, depending on the circumstances.

The use of certain weapons, including chemical ones, is also prohibited.

Cluster munitions, which scatter bomblets indiscriminately and leave unexploded duds that pose dangers to civilians after the conflict, are banned by many nations — but not Russia and Ukraine. Russia’s alleged use of those weapons in Ukraine, as well as “vacuum weapons,” isn’t automatically illegal, Schabas said. That determination depends on whether Russia took steps to avoid harming civilians.

What are cluster and vacuum weapons, and how has Russia used them in the past?

There is also a separate legal category of crimes against humanity, which includes mass murder, enslavement and torture. Genocide is another crime over which the ICC has jurisdiction. A 1948 legal convention defined it as an independent crime that consists of killing, causing “serious bodily or mental harm,” preventing births or forcibly transferring children of a group “with intent to destroy, in whole or in part, a national, ethnical, racial or religious group.” Imposing living conditions intended to physically destroy a group, fully or partially, also counts as genocide.

“Unfortunately there is a real disconnect between the legal use of the term genocide and the way that genocide is understood in popular discourse,” said Rebecca Hamilton, an international law professor at American University and a former lawyer in the ICC’s prosecutor’s office.

Genocide is often used by members of the public “to describe a situation that is horrific, that feels unimaginable, where it seems that civilians are being killed for no reason other than the fact that they are, in this case, Ukrainian,” she said. “But the legal definition of genocide is very specific and we are not at a stage yet where enough evidence has been gathered to make a legal assessment of whether genocide is occurring.”

International law around conflict governs more than just combat. Ukraine has adopted the tactic of posting photos and videos of captured and killed Russian soldiers online, which could be a violation of the Geneva Conventions.

Who has the power to investigate?

As long as Ukraine’s justice system is functional, Ukrainian authorities have the primary responsibility to investigate alleged violations of international law committed on Ukrainian territory, said James Gow, professor of international peace and security at King’s College London.

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Another avenue: the International Criminal Court.

Neither Ukraine nor Russia is a party to the court, so neither can bring allegations to prosecutors. But Ukraine has twice accepted the court’s jurisdiction over its territory — and other countries can refer alleged crimes there to the court. Karim Khan, the ICC’s chief prosecutor, said in early March that his office received referrals from 39 countries.

Khan announced that he was opening an investigation into allegations of war crimes, crimes against humanity or genocide in Ukraine “by any person” from November 2013 onward.

A preliminary investigation found “reasonable basis to believe crimes within the jurisdiction of the Court had been committed” and “identified potential cases that would be admissible,” Khan said in a statement.

Separately, the United Nations’ top human rights body voted to set up a commission to probe alleged Russian rights violations during the invasion. The Biden administration announced support for a multinational team of prosecutors that would visit the region to collect evidence of atrocities, while French prosecutors on April 5 opened three probes into potential war crimes committed by Russian soldiers against French nationals in Ukraine.

What evidence is required to prosecute perpetrators?

A large quantity and it has to be solid.

ICC investigators have begun collecting evidence, and Khan appealed for countries to give his office additional resources.

Eliot Higgins, the founder of open-source group Bellingcat, told the Guardian that his organization was working with others to preserve evidence of potential war crimes that would be accepted in court.

The world is watching the war unfold in real time, as a flood of videos across Facebook, Telegram, TikTok and Twitter show the destruction left by apparent cluster munitions and strikes on a TV tower close to a Holocaust memorial in Kyiv. Human rights groups and journalists have verified and published eyewitness and social media accounts of attacks on civilian areas.

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Social media documentation can help in investigations. But the bar for evidence in war crimes cases is high, international law experts say.

War is a bloody business, and civilian casualties are expected. In many cases, proving that the killing of civilians constitutes a war crime requires showing the attacker’s intent to harm civilians or strike forbidden targets such as hospitals and schools. So holding top officials accountable typically requires intercepting communications up the chain of command, Gow said.

“Proportionality” is a subjective standard that isn’t clearly defined, Schabas said — and Ukraine’s defense tactics, including the fortification of residential neighborhoods in Kyiv, give Russia legal cover for attacking civilian areas.

Russia has killed civilians in Ukraine. Kyiv’s defense tactics add to the danger.

“Crimes on the battlefield are very hard to prove,” he said. “There have been very few successful prosecutions for those types of crimes.”

Building a case is further complicated by increasingly blurred lines between civilians and fighters. Ordinary Ukrainians have taken up arms and gathered to make Molotov cocktails. They lose their status as civilians under international law when they’re fighting, Schabas said.

Could Russian officials be held accountable?

Shortly after Putin launched his invasion, calls for accountability began ricocheting across the world.

World leaders have faced trial for war crimes in the past. In a famous example, an international court put the president of the former Yugoslavia, Slobodan Milosevic, on trial in 2002 for war crimes and crimes against humanity in the Balkan wars of the 1990s. Milosevic died in custody before the trial concluded.

But even if the evidence is there, putting Russian officials — let alone Putin — on trial is unlikely, barring major political change in Russia, Gow said. As long as the Russian government remains unwilling to cooperate, and Russians accused of crimes don’t travel abroad, there’s not much international prosecutors can do.

Still, it’s valuable to collect and preserve evidence of potential war crimes and crimes against humanity, Gow said, since circumstances in Russia may change.

“No one likes to be branded a war criminal, so there is [an] important potential psychological and political effect to be gained contingently from investigations,” he said.

And even if the perpetrators of any war crimes in Ukraine do not face punishment, stockpiling evidence can serve as a crucial corrective to false narratives.

The international tribunal that tried Milosevic said the “greatest achievement” of the proceedings was making reams of evidence available to the public as “a barrier against malign attempts to revise history.”

Erin Cunningham, Miriam Berger and Amber Phillips contributed to this report.