While investigating links to money laundering and drug trafficking, he was imprisoned on charges of terrorism; he was beaten and mistreated in prison, but later found innocent of all charges.
Halvorssen's case was taken up by Amnesty International and several other international human rights organizations.
The set-up of Halvorssen was reportedly payback for his investigations into presidential corruption, mafia activity, and the money laundering activities of Colombian drug kingpin Pablo Escobar.