Benjamin Berell Ferencz March 11 1920 April 7 2023 was an American lawyer He was an investigator of Nazi war crimes after World War II and the chief prosecutor for the United States Army at the Einsatzgruppen Trial one of the 12 Subsequent Nuremberg Trials held by the US authorities at Nuremberg Germany Later he became an advocate of international rule of law and for the establishment of an International Criminal Court From 1985 to 1996 he was an adjunct professor of international law at Pace University