Explainer: How could Putin be prosecuted for war crimes?

US President Joe Biden has publicly called Russian President Vladimir Putin a war criminal, but legal experts said the prosecution of Putin or other Russian leaders would face high hurdles and could take years, as outlined below:
How is a war crime defined?
The International Criminal Court (ICC) in The Hague, Netherlands, defines war crimes as "grave breaches" of the post-World War Two Geneva Conventions, agreements which laid out the international humanitarian laws to be followed in wartime...