Jailed Norwegian mass murderer Anders Behring Breivik has given a Nazi salute upon returning to court to argue that his isolation violates his rights.
The right-wing extremist compared his imprisonment to “torture” but the state says he is being treated fairly.
Breivik killed 77 people in 2011 when he bombed central Oslo before going on a shooting spree at a Labour Youth camp on the island of Utoya.
Tuesday’s hearing, in a prison gym converted into a court, marks his first public appearance since then.
He entered the court in a grey suit shortly before 09:00 (08:00 GMT). He shook hands with his lawyers and made the Nazi salute after police removed his handcuffs.
Breivik, 37, is mainly challenging the government over his solitary confinement, as well as over general conditions, including what he claims is the excessive use of handcuffs.
In his opening statement, Breivik’s lawyer Oystein Storrvik said his client’s punishment was worse than the death penalty, which is outlawed in Norway.
Breivik accuses the Norwegian government of breaching two clauses of the European Convention on Human Rights.
One of the clauses guarantees the right to respect for “private and family life” and “correspondence”, while the other prohibits “inhuman or degrading treatment or punishment”.
Mr Storrvik earlier told AFP news agency that Breivik had been “very stressed due to his isolation” in Skien prison, about 100km (60 miles) south-west of the capital Oslo.
“One of his main things to do (in prison) was to study and he has stopped that now, and I feel that is a sign that isolation has been negative to his psychological health,” he said.
Authorities say Breivik’s correspondence is censored to stop him setting up an “extremist network”. His visits are almost all with professionals across a glass partition.
The attorney general’s office has insisted that Breivik’s prison conditions are “well within the limits of what is permitted” under the convention.
The court hearing is expected to run until Friday. Breivik is expected to testify on Wednesday.
If the court decides that Breivik’s prison conditions are so strict that they cause him harm and violate his human rights, it could order an easing of restrictions.
Last September, Breivik threatened to starve himself to death in protest at his treatment in prison.
His cell at Skien prison has a TV and computer but he has no access to the internet.
In a letter to media outlets in Norway and Sweden, he said he was kept in almost total isolation, with time outside his cell limited to one hour a day.
He said the harsh prison conditions had forced him to drop out of a political science course at the University of Oslo.
Breivik was first held at Ila Detention and Security Prison near Oslo before being moved to Skien in 2013. At Ila, he also complained of being held in “inhumane” conditions.
In a letter to prison authorities, he said his cell was poorly decorated and had no view. He also complained that his coffee was served cold, he did not have enough butter for his bread, and he was not allowed moisturiser.