From 3 to 6 April, the tribunal cross-examined Field-Marshal Wilhelm Keitel, Chief of the German High Command. The main military leader of the Reich did not deny responsibility for violations of international law but emphasised that he was following the orders of Adolf Hitler and could not resign. Keitel denied accusations of war crimes, but how can one dismiss his own signature on a criminal order?

Source: 

Nuremberg Trials Stenograph. Volume IX, Second Edition (2019). Translated from English by Sergei Miroshnichenko.