The decision will determine whether Breivik, who massacred 77 people, can be held criminally liable and punished with a prison sentence.
If not, he could be sent to a psychiatric ward for treatment instead.
The bomb in Oslo and the shooting spree on the island of Utoya on July 22 were so carefully planned and executed that it would be difficult to argue they were the work of a delusional madman, said Dr Tarjei Rygnestad, head of the Norwegian Board of Forensic Medicine.
Breivik's lawyer has said there are indications his client is insane. But Mr Rygnestad said the attacks were too complicated for someone suffering from psychosis, a requirement, under Norwegian law, for a plea of insanity. Read More