At the first Nuremberg trial, twenty-one defendants were tried in person: Karl Dönitz, Hans Frank, Wilhelm Frick, Hans Fritzsche, Walther Funk, Hermann Göring, Rudolf Hess, Alfred Jodl, Ernst Kaltenbrunner, Wilhelm Keitel, Konstantin von Neurath, Franz von Papen, Erich Raeder, Joachim von Ribbentrop, Alfred Rosenberg, Fritz Sauckel, Hjalmar Schacht, Baldur von Schirach, Arthur Seyss-Inquart, Albert Speer, and Julius Streicher.
The official trial languages were English, German, French, and Russian. The participants (including the German-speaking defendants) were provided with headphones for simultaneous translation. However, in many photographs of the proceedings, not all of the defendants are wearing headphones. While it may be the case that these defendants simply weren't paying attention, or that they had removed their headphones during a lull in the proceedings, it may also be the case that they already had a sufficient command of the foreign language(s) being spoken.
Which of the Nuremberg defendants could already speak English, French, or Russian at the time of the trial? And of those who survived the trial, did any of them later learn English, French, or Russian?
I know only part of the answer already: there are video recordings of Karl Dönitz speaking English, and Albert Speer speaking French and English. However, these were made long after the war, so I don't know whether they understood these languages during their trial.