In August 1945 Great Britain, France, the USSR and the United States established a tribunal at Nuremberg to try military and civilian leaders of the Nazi regime for the plotting of aggressive warfare, the extermination of civilian populations, the widespread use of slave labor, the looting of occupied countries, and the maltreatment and murder of prisoners of war. G. M. Gilbert was the prison psychologist before and during the Nuremberg trial. He had an unrivalled, firsthand opportunity to watch and question the Nazi war criminals. With scientific dispassion he encouraged Goering, Speer, Hess Ribbentrop, Frank, Jodl, Keitel, Streicher, and the others to reveal their innermost thoughts.