Anders Behring Breivik wants to tell Norway and the world why he killed at least 93 people in a bomb attack and shooting rampage when he appears in court on Monday, his lawyer said.
Calling himself a crusader against a tide of Islam in a rambling 1,500-page online manifesto, the 32-year-old mass murderer wants the opportunity to explain actions he deemed 'atrocious' but 'necessary'.
The judge will have to decide whether the custody hearing, expected to start after 1pm (1100 GMT), will be held in public or behind closed doors.
The issue has generated a debate about freedom of expression with many Norwegians opposed to allowing a man who has shaken the nation's psyche to expound his views.
Breivik has asked to wear a uniform in court, but his lawyer, Geir Lippestad, said he did not know what type. The killer was dressed as a policeman during his shooting spree.
His lawyer said that it was not clear what sort of uniform he wanted to wear. Breivik has not served in the armed forces but in some of the pictures he posted on the internet before his killing spree he was dressed in a military-style outfit.
Police did not confirm a local media report that they planned to request a closed hearing. "It's up to the judge to decide. It's not uncommon that the police will ask for it in advance but I don't know if the police will ask for that," Liv Corneliussen, a police prosecutor, told Reuters.
Lippestad said that his client had admitted to Friday's shootings at a Labour youth camp and an earlier bombing that killed seven people in Oslo's government district, but that he denies any criminal guilt.
"He has been politically active and found out himself that he did not succeed with usual political tools and so resorted to violence," Lippestad told TV2 news.
"I await a medical assessment of him," he said.
The worst peacetime massacre in the normally placid country's modern history appears to have been driven by Breivik's mission to save Europe from what he saw as the threats of Islam, immigration and multi-culturalism.
That he surrendered to police when finally confronted on the tiny island of Utoeya after shooting dead 86 youngsters underlines his desire to secure a public platform for his radical thoughts.
In other instances of gunmen going on killing sprees the perpetrators often commit suicide when the police arrive or actively provoke officers to shoot them dead.
Breivik wrote in his manifesto, posted hours before his attacks, that if he survived his assault and was arrested, this would "mark the initiation of the propaganda phase".
Norwegian newspapers focused on the victims as shock turns to mourning, giving chilling new accounts of the island massacre and focusing on acts of bravery which saved lives.
The main broadsheet Aftenposten led with "Sorrow unites Norway" and printed a picture of a central Oslo square filled with flowers and lit candles in remembrance of the dead.
The newspaper's commentator Harald Stanghelle said Breivik should not be allowed to turn the courtroom into his pulpit.
Daily Dagsavisen asked "Why didn't you come earlier?" citing screams by youth as police arrived on Utoeya island on Friday - an hour after they were notified of the shooting.
Norwegian markets will open as normal, but the country will observe a minute of silence at midday (1000 GMT).
"He explains himself fairly calmly, but every now and then expresses emotion," Lippestad said of Breivik. "He buries his head in his hands."
"He has said that he believed the actions were atrocious, but that in his head they were necessary," adding his client did not feel he deserved punishment.
Police believe Breivik acted alone after losing faith in mainstream parties, even those that have gained popularity and parliamentary seats on anti-immigration policies in otherwise liberal, tolerant European nations, including affluent Norway.
The attack was likely to tone down the immigration debate ahead of September local elections, analysts said, as parties try to distance themselves from Breivik's beliefs and reinforce Norwegians' self-image as an open, peaceful people.
Norway's immigrant numbers nearly tripled between 1995 and 2010 to almost half a million in a population of 4.8 million.
The sense that many were drawn by Norway's generous welfare handouts helped spur the growth of the Progress Party which became Norway's second biggest in parliament after the 2009 election on a largely anti-immigration platform.
Breivik was once a member of the party, but left complaining it was too politically correct. It was then he began scheming to "resist", burying ammunition more than a year ago, weight-lifting, storing up credit cards and researching bomb-making while playing online war games.
After three months of laboriously pounding and mixing fertiliser, aspirin and other chemicals on a remote farm, Breivik drove a hire car packed with the results to the centre of Oslo on Friday, triggering the device outside government offices, killing seven and shattering thousands of windows.
He then drove to the small island of Utoeya, 45 km (28 miles) away. Dressed as a policeman, he calmly shot down youngsters at a youth summer camp of the ruling Labour Party. His terrified victims tried to hide under beds or in the woods. Some leapt into the lake and tried to swim to the mainland.
"This is going to be an all-or-nothing scenario," Breivik wrote in his English-language online journal on the morning of the attack. "First coming costume party this autumn, dress up as a police officer. Arrive with insignias:-) Will be awesome as people will be very astonished:-)."
A surgeon at a hospital that treated 35 of the wounded said Breivik may have used "dum-dum" bullets for maximum damage.
"These bullets don't explode inside the body but fragment into pieces more quickly than other bullets," Colin Poole, chief surgeon of the Ringerike district hospital, told Reuters.
While Breivik was stalking his prey on Utoeya, it took police a full hour to get a team of elite forces to the island after one boat, overloaded with officers and equipment, was forced to stop when it began to take on water.
Norwegian television managed to charter a helicopter and filmed the killer before the police showed up. When the armed team did arrive, Breivik gave himself up without a fight.
"He had at that point used two weapons and had been, and was still, in possession of a substantial amount of ammunition," Johan Fredriksen, chief of staff at Oslo police. "Thus, the police's response has hindered further killing on the island."
At the custody hearing police can request an initial detention of eight weeks in solitary confinement with no access to news, letters or visitors, except a lawyer. Police have said a trial could be a year away.
The maximum jail term in Norway is 21 years, although that can be extended if there is a risk of repeat offences.
"In theory he can be in jail for the rest of his life," said professor of criminal law at the University of Oslo, Staale Eskeland.