Psychiatrists are expected to submit their report on Norwegian mass killer Anders Behring Breivik.

The 32-year-old gunman faces a lengthy prison sentence if the 230-page report establishes that he was sane and in control of his actions when he killed 77 people in July.

Breivik, who has pleaded not guilty to terror charges, has nonetheless admitted the attacks in Oslo and on the island of Utoeya. The far-right extremist insisted his actions were "atrocious but necessary" and that he had been on a crusade against the "Muslim invasion" of Europe and growing multiculturalism

Eight people were killed in Oslo after he detonated a car bomb close to government buildings while disguised as a police officer. In the deadliest attack in Norway since World War II, he also killed 69 young supporters of the Labour Party in a shooting rampage on Utoya island.

The young victims, who ranged in age from 16 to 22, were attending a youth camp organised by the ruling party.

The 32-year-old Breivik made his first public appearance since the incidents when he appeared at Oslo District Court a fortnight ago. According to the judge, the gunman "is not insane" and there is no evidence that he had collaborators in either the bombing or the massacre.

A recording leaked this week of a call Breivik made to Norwegian emergency services has triggered a controversy over the speed at which police responded to the massacre. In the 30-second call, which is believed to have been made half way through the massacre, Breivik tells the operator he is willing to surrender. The carnage on the island nevertheless continued unabated.

In the phone call, Breivik introduces himself as a commander of the "Norwegian anti-Communist resistance movement". After telling the operator that he wants to surrender, he hangs up and continues killing. This has fuelled the hypothesis that the cold, calculating Breivik may have hesitated momentarily before continuing to carrying out his murderous plan.

The alleged slow response by police has raised questions over why the authorities took an hour to reach the island and stop the massacre.