In a speech before the United Nations, Ukrainian President Volodymyr Zelensky accused Russia of the worst war crimes since World War II. But whether there will be accountability on the international stage is a separate question—especially with Russia sitting permanently on the UN Security Council.  How difficult would it be to prove war crimes have in fact been committed in Ukraine? And even if they were, would Putin ever actually be punished?  Guest: Stephen Rapp, former United States Ambassador-at-Large for War Crimes Issues in the Office of Global Criminal Justice under President Obama. If you enjoy this show, please consider signing up for Slate Plus. Slate Plus members get benefits like zero ads on any Slate podcast, bonus episodes of shows like Slow Burn and Dear Prudence—and you’ll be supporting the work we do here on What Next. Sign up now at slate.com/whatnextplus to help support our work. Learn more about your ad choices. Visit megaphone.fm/adchoices