He was a jurist was in service at Reich ministry of justice before the rise of Nazi power.He collected evidence during the night of long knives in which official murders took place at the order of Hitler. and he became anti Nazi resistance group member during WW II owing to mass murders of Jews and other prisoners and official organized crime. He was sent to Abweher the intelligence organization of Wehrmacht under Admiral Canaris which was the nerve center for anti Nazi activities.He helped some Jews to escape from Germany with their loved ones to Switzerland making forged papers and even arranged money for them to get on. He clandestinely went to Switzerland and ensured that everything went smooth and returned.He was part of Gen Trescaw's assassination attempt on Hitler much before 20 July plot in which a bomb was placed in the air craft in which Hitler traveled to a forward area. Luckily for him the bomb did not go off. When the 20 July plot failed, Dohnanyi was arrested along with others. He was tried on 06 April 1945 at Hitlers orders by a special SS court Drum heads and was sentenced to death although he was lying semi conscious on stretcher. He was executed by hanging using piano wire on 8 or 9 April 1945.