Hagen served as personal assistant to the SS police chief in Paris Carl Oberg, heading the Gestapo department.

In 1980 after a change in the law to allow retrial of cases handled abroad, he was sentenced to 12 years in prison by a Cologne court, for his key role in the deportation of 73,000 Jews to the Auschwitz death camp.

Because he belonged to the SS and SD, Hagen was sentenced to one and a half years in prison on 5 May 1948, which was considered served due to his time in internment.

[4] On 18 March 1955, in light of new evidence, a military court in Paris found him guilty of being instrumental in the deportation of the Jews from France, he was sentenced (in absentia) to lifelong forced labour.

In 1980, after 15 months of trial, Herbert Hagen was tried and convicted by the 15th criminal chamber of the Cologne Higher Regional Court and sentenced to twelve years in prison on charges of ordering and administrating the deportation of Jews.