Two psychiatrists have been asked to determine whether 32-year-old right-wing extremist Anders Behring Breivik was sane when he committed the attacks, and that evaluation will in turn determine whether he is sentenced to prison or psychiatric care.
Their report, which has been delayed by a month at their request, will be handed to the Oslo court at 9am, and the prosecutor's office is expected to reveal the main points at a press conference at 1pm.
Behring Breivik is currently begin detained in a high-security prison near Oslo. His trial is scheduled to open on April 16th, 2012 and last for about 10 weeks.
The maximum prison sentence for this type of crime under Norwegian law is 21 years, but Behring Brevik could stay behind bars longer if he is still considered a threat to society.
On July 22, Behring Breivik first set off a car bomb outside the government buildings in Oslo that house the offices of Prime Minister Jens Stoltenberg, killing eight people.
After that, he went to the island of Utøya, some 40 kilometres northwest of Oslo, where, disguised as a police officer, he spent nearly an hour and a half methodically killing another 69 people, most of them teenagers.
Although he has confessed to the facts, Behring Breivik has refused to plead guilty, insisting his actions were "atrocious but necessary."
He has claimed to have been on a crusade against multiculturalism and the "Muslim invasion" of Europe.