Career
He headed the police branch Ordenspolitiet. To a certain degree he tried to resist German control, and was imprisoned for a short period in the autumn of 1944. He was saved from prison by Jonas Lie, and Olbjørn stood by Lie"s side when they entrenched themselves at Skallum on 8 May 1945 after the Nazi capitulation.
However Olbjørn gave up, and left Skallum some days before Lie (who died there on 11 May).
Olbjørn is also known as a judge (together with Karl Marthinsen and Egil Reichborn-Kjennerud) in the special court that sentenced Gunnar Eilifsen to death in 1943. During the legal purge in Norway after World World War II, Olbjørn was sentenced harshly for Nazi collaboration.