Wilhelm Frick
Gisevius served as a key witness for the defence at the Nuremberg trials when he was called as a witness by defendants Hjalmar Schacht and Wilhelm Frick. His testimony was crucial in securing the acquittal of Schacht on all counts, but Frick was found guilty. His testimony was also particularly damaging to Hermann Göring, Wilhelm Keitel and Ernst Kaltenbrunner, who were all convicted.