Washington(CNN) Airstrikes on an art school and a maternity hospital. Residential apartment buildings taking fire from tanks. More than 900 civilians killed in a matter of weeks.
Is Russian President Vladimir Putin a war criminal? His country's unprovoked and brutal invasion of Ukraine has presented reams of evidence that have led some world leaders -- including US President Joe Biden last week -- to use the loaded label.
The question now is what Biden's comments -- which he followed up by calling Putin a "murderous dictator" and "pure thug" -- will mean for the war in Ukraine going forward.
Ukrainian President Volodymyr Zelensky on Sunday didn't signal any concern that Biden's remarks would roil talks with Russia. He told CNN's Fareed Zakaria that he's "ready for negotiations" with Putin. (More on this in a minute.)
Biden's comments represented a major moment since leading officials had mostly avoided saying war crimes were being committed in Ukraine, citing ongoing investigations into whether that term could be used. But soon after the President uttered the words "I think he is a war criminal" to reporters at an unrelated event, White House press secretary Jen Psaki said the comment was "from the heart." Other officials used similar language.
"When you are speaking from the heart, speaking as a human and you're seeing what we've all seen, these searing images on TV, a Russian strike on a maternity hospital in Mariupol, strikes against residential buildings, against schools, against civilian neighborhoods, it's hard not to walk away with that conclusion," State Department spokesman Ned Price later told CNN.
And after Secretary of State Antony Blinken said he "personally" agreed with Biden's label of Putin, Psaki told reporters that the top US diplomat was speaking from the heart "as well."
Why all the parsing? While terms like "war crimes" and "war criminal" are often used colloquially, they do have a legal definition that could be used in potential prosecution. That includes in the Geneva Conventions, which specify intentional targeting of civilians as a war crime.
In other words, the White House is being careful to not get ahead of the international investigations probing Russia's invasion.
Will Biden's words complicate Ukraine-Russia negotiations? The Kremlin called Biden's remarks about Putin being a war criminal "absolutely unacceptable and inexcusable."
Asked if it would be hard to sit down with Putin, Zelensky maintained Sunday that he's ready -- and has been ready.
"I'm ready for negotiations with him. I was ready for the last two years. And I think that without negotiations we cannot end this war," he said on CNN's "Fareed Zakaria GPS."
"I think that we have to use any format, any chance, in order to have a possibility of negotiating, possibility of talking to Putin. But if these attempts fail, that would mean that this is a third World War."
Zelensky has urged more negotiations in recent days as Russia's invasion of Ukraine nears its fourth week. In a video message posted Saturday, he called for talks "without delay," warning that otherwise Russia's losses would be "huge."
The problem, as CNN's national security team reports, is that US and NATO officials believe Putin has not backed off his original demands in talks with Ukraine, and there is a heavy dose of skepticism in Western capitals about how credible Moscow's engagement truly is -- even as the status of those negotiations remains difficult to decipher, according to multiple sources briefed on the situation.
Ukrainian and Russian negotiators have met four times since the start of Russia's invasion.
The view from the State Department. US Deputy Secretary of State Wendy Sherman on Friday also expressed her personal view that war crimes are being committed in Russia, saying that they "all feel it personally," but noted that there must be "a body of proof" before a legal determination can be made.
"I think there is virtually no one -- maybe Vladimir Putin is the exception -- who can look at all of the photographs, all of video coming from Ukraine and not believe that Putin is intentionally targeting civilians, and intentionally targeting civilians is a war crime," she said in an interview with CNN's John Berman on "New Day."
"Now, I think we all feel it personally," Sherman said, "but in terms of international law, you have to have evidence, you have to have a body of proof that in fact there was intentionality." She added that the United States is "helping to pull that evidence together, present it to international justice parties and then have a legal threshold that is met."
How long do war crime investigations take? Investigations at the International Criminal Court take many years, and only a handful of convictions have ever been won.
Put differently, it could be a while before Biden's "war criminal" remarks have any legal weight -- if ever.
As we noted earlier this month, the court tries people, not countries, and focuses on those who hold the most responsibility: leaders and officials. While Ukraine is not a member of the court, it has previously accepted its jurisdiction. Putin could, therefore, theoretically be indicted by the court for previously ordering war crimes in Crimea.
However, the ICC does not conduct trials in absentia, so he would either have to be handed over by Russia or arrested outside of Russia. That seems unlikely.