How to prove genocide, the gravest of war crimes?

Washington and Kyiv are accusing Russia of genocide in Ukraine, but the ultimate war crime has a strict legal definition and has rarely been proven in court since it was cemented in humanitarian law after the Holocaust.

What is genocide?

The 1948 Genocide Convention defines genocide as crimes committed "with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such."