AN Oslo court will hand down its verdict on Friday against Anders Behring Breivik for his twin attacks last year that left 77 people dead, bringing to a close one of the most spectacular trials in Norway's history.

The rightwing extremist has confessed to the attacks so there is no doubt about his guilt, but the question of his sanity was the focus of his 10-week trial that wrapped up in June.

On Friday, the five judges at the Oslo district court will announce whether they consider the 33-year-old legally responsible for his crimes, which determines whether he will spend a long sentence behind bars or in a closed psychiatric ward.

On July 22, 2011, Breivik set off a car bomb outside the government offices in Oslo, killing eight people, before going to the island of Utoeya, northwest of the capital, where he spent more than an hour gunning down another 69 people, mostly teenagers, attending a Labour Party youth camp.

The attacks traumatised the normally-tranquil nation, and highlighted authorities' lack of preparedness.

Norway's national police commissioner resigned last week after a scathing report on the response to the attacks, and Prime Minister Jens Stoltenberg is due to appear before an extraordinary parliamentary session to discuss the report at the end of the month.

Charged with "acts of terror", Breivik could possibly be sent to closed psychiatric care for life. Or he could be sentenced to up to 21 years in prison, the maximum sentence in Norway though it could be extended indefinitely as long as he is considered a danger to society.

While Breivik has confessed to the crimes he pleaded not guilty, arguing that his actions were "cruel but necessary" to protect his country from multiculturalism, which was embraced by his victims.