After 1945 Exner was unusual among his colleagues in retaining his professorship under . He had kept his job under the Hitler government but had never been a "Nazi Party" member. During the "Denazification programme" that followed, the new rulers determined that he was "politisch unbelastet" ("politically unencumbered"). By the time he died in 1947 he was one of a very small number of well known criminologists to have studied and taught under no fewer than four contrasting ruling establishments: the (1) Danube Monarchy till 1918, the (2) German Republic till 1933, the Populist-nationalist Dictatorship till 1945 and the (4) Stalinist annexations and military occupation that followed. After the launch of the German Federal Republic (West Germany) in 1949 it transpired that his reputation would remain, if not untarnished, at least broadly intact under a fifth ruling establishment.