According to The Buchenwald Report, Col. Koch was arrested in August 1943 by the Nazis for inciting the murder of two prisoners, for embezzlement and black market activities in the camps. The prosecutor was SS judge Konrad Morgen, who was on a mission himself. After a six-month investigation both Koch and his wife were condemned to death. The execution took place on April 5, 1945, one week before American liberators arrived.
His second wife was Ilse Koch, whom he married in 1936, better known as The Witch of Buchenwald ("Die Hexe von Buchenwald"). Sentenced to life imprisonment by a German tribunal after the war, she committed suicide in prison in 1967