A veteran human rights lawyer who prosecuted the trial of former Serbian President Slobodan Milosevic says Russians could be tried for war crimes over their actions in Ukraine.
Geoffrey Nice, who prosecuted several cases at The Hague-based International Criminal Tribunal for the Former Yugoslavia (ICTY), told RFE/RL's Balkan Service that building a war crimes indictment relating to Ukraine "is a substantial task" but "not necessarily" difficult.
"It's very, very important for Ukraine, and Ukrainians, not to think that the process of building an indictment -- and then possibly having someone tried -- needs to take years," he said. The work of the ICTY was often criticized for being too slow, its efforts hampered by countries refusing to give up their citizens accused of war crimes.
Since February 24, when Russia launched an unprovoked invasion of Ukraine that has killed thousands of civilians, Russian troops have been accused of committing war crimes.
In Bucha, a suburb of Kyiv, the Ukrainian capital, hundreds of civilians were found dead after the withdrawal of Russian forces, with many of them lying in the street with their hands tied. Russia has repeatedly bombarded residential buildings across Ukraine and, on April 8, Russian forces fired a missile at a crowded train station in the eastern city of Kramatorsk, killing at least 52 people.
The longest running war crimes court ever, the ICTY was created in 1993 by the UN Security Council in response to the "horrific crimes" and "grave breaches" of the Geneva Conventions that were taking place across the former Yugoslavia, where at least 130,000 people died in a series of conflicts that blighted the 1990s. In total, the ICTY sentenced 90 war criminals to prison terms before passing its final judgment in 2017.
In Ukraine, a war crimes investigation has already begun.
On February 28, Karim Khan, a prosecutor at The Hague-based International Criminal Court, announced that a war crimes investigation was under way for which evidence was already being collected. Neither Russia nor Ukraine are parties to the ICC, although Ukraine does recognize the court's jurisprudence. The United States is also not a party to the ICC.
Any war crimes investigation in Ukraine is unlikely to be hampered by a lack of evidence. Nice, a British barrister who has focused on human rights work for much of his career, is optimistic about the amount of evidence that already exists regarding potential war crimes taking place in Ukraine.
"You build the indictment for a trial by obviously accumulating all the evidence that you can," Nice said. "There is stacks of it: Everybody using their mobile telephones as cameras, the journalists being on the ground in all the relevant centers of the conflict."
And, as Nice pointed out, Russian President Vladimir Putin does not seem to deny this evidence.
"If he wants to say any of that was done by a rogue group out of his control or not following his instructions, then he would have said that, and he should immediately have recalled the troops to Moscow for trial," Nice said. "Has he done that? No, he hasn't. Why not? Because they're doing what he wanted."
At the ICC, defendants can face charges of war crimes, crimes against humanity, and genocide. A war crime occurs when a combatant violates the laws of war by, for example, killing or raping civilians. Crimes against humanity are committed not by an individual but by a state and must be motivated by the pursuance of a policy.
Ukrainian President Volodymyr Zelenskiy has said that Russian actions on the ground have amounted to "genocide," although U.S. and Western leaders have been more cautious in using that term.
WATCH: Ukrainian authorities exhumed dozens of bodies from mass graves in the Kyiv suburb of Bucha for forensic tests and to prepare them for proper burial. There is strong evidence that Russian forces committed war crimes in the town. The head of Ukraine's National Police told RFE/RL on April 8 that many victims were shot in the temple at point-blank range.
The Convention on the Prevention and Punishment of the Crime of Genocide, which was adopted by the UN Security Council in 1948, states that genocidal acts have to be "committed with intent to destroy, in whole or in part, a national, ethnic, racial, or religious group."
Despite the sheer amount of evidence coming out of Ukraine, Nice says the crime of genocide can be very hard to prove, as it is necessary to determine the thoughts and motives of the accused. Proving that Putin's intention was to kill Ukrainians simply because they're Ukrainian wouldn't be easy.
To convict of genocide, "you [have] to exclude all sorts of other possible states of mind and all sorts of possible intentions," Nice said. "We're doing what we're doing simply because we want to expand our territorial limits," he cited as an example of a possible defense, or "because we want to retain our perceived historic borders."
That doesn't mean it can't be done.
The International Court of Justice, the principal judicial organ of the United Nations, ruled in 2006 that the events at Srebrenica -- where some 8,000 Bosnian Muslim men and boys were killed by Bosnian Serbs -- constituted genocide.
While the "genocide" debate arouses intense passions, Nice reminded that a label of genocide "doesn't actually make the crime any more serious necessarily than war crimes or crimes against humanity." Whatever the label, the act of violence -- and its consequences -- are the same.
"I think the easiest crimes to prove in [Ukraine's] case will be crimes against humanity and war crimes," he said.
The elephant in the room is, of course, Russia -- and Putin.
Depending on how the war ends, Moscow could be the biggest obstacle for any war crimes trials by not handing over those accused. The ICC doesn't have a police force and doesn't hold trials in absentia, so its options are limited. One of the main problems with the Yugoslav trials, Nice said, was that suspects weren't handed over by their parent states for decades. In the case of Putin, a trial would be unlikely, especially given that the ICC has never tried a sitting head of state.
Nice said it is crucial now to ensure that as much as possible is documented and in the public record, for journalists and civilians to bear witness, so that an "evidence-based record of criminality is left as soon as possible."
"Ukraine has been terrific at being on the moral high ground. And it just now needs to reinforce that by having every politician saying that these are war crimes," he said.
It's very important, said Nice, that "a record is properly made, kept, and made public…and then kept in public, that shows precisely from the beginning that this was a criminal act."