Explained | Who's a war criminal, and who gets to decide?

U.S. President Joe Biden called Russian President Vladimir Putin a war criminal

U.S. President Joe Biden on Wednesday flatly called Russia's Vladimir Putin a “war criminal” for the unfolding onslaught in Ukraine, where hospitals and maternity wards have been bombed. But declaring someone a war criminal is not as simple as just saying the words. There are set definitions and processes for determining who's a war criminal and how they should be punished.

The White House had been avoiding applying the designation to Mr. Putin, saying it requires investigation and an international determination. After Mr. Biden used the term, White House press secretary Jen Psaki said the President was “speaking from his heart" and renewed her statements that there is a process for making a formal determination.

In popular usage, though, the phrase has a taken on a colloquial meaning as a generic term for someone who's awful.

“Clearly Putin is a war criminal, but the President is speaking politically on this,” said David Crane, who has worked on war crimes for decades and served as chief prosecutor for the U.N. Special Court for Sierra Leone, which tried former Liberian President Charles Taylor.

The investigations into Mr. Putin's actions already have begun. The U.S. and 44 other countries are working together to investigate possible violations and abuses, after the passage of a resolution by the United Nations Human Rights Council to establish a commission of inquiry. There is another probe by the International Criminal Court, an independent body based in the Netherlands.

“We're at the beginning of the beginning,” said Mr. Crane, who now heads the Global Accountability Network, which works with the international court and United Nations, among others. On the day of the invasion, his group set up a task force compiling criminal information for war crimes. He's also drafting a sample indictment against Mr. Putin. He predicted an indictment of Mr. Putin could happen within a year. But there is no statute of limitations.