Breivik has sued the state, claiming his extended isolation is a violation of Article 3 of the European Convention on Human Rights, which prohibits “inhumane” and “degrading” treatment.

Now 44, he has been held apart from other inmates in high-security facilities for over 11 years.

The trial, which opened on Monday, is being held for security reasons in the gymnasium of Ringerike prison where Breivik is serving his sentence.

More than 12 years after committing the bloodiest attack on Norwegian soil since World War II, Breivik still poses “an absolutely extreme risk of totally unbridled violence”, the state’s lawyer Andreas Hjetland told the court.

On July 22nd, 2011, Breivik set off a bomb near government offices in Oslo, killing eight people, before gunning down 69 others, mostly teens, at a Labour
Party youth wing summer camp on the island of Utoya.

He was sentenced in 2012 to 21 years in prison, which can be extended as long as he is considered a threat, which was Norway’s harshest sentence at the time.

“Breivik represents the same danger today as on July 21st, 2011,” the eve of the twin attacks he prepared meticulously for years, Hjetland said, citing
assessments written by psychiatrists and prison wardens.

“His ideology remains the same, his aptitude for unlimited violence is evident and his personality… further reinforces all these factors,” he said.

On Monday, Breivik’s lawyer Oystein Storrvik had asked for an easing of his client’s prison conditions, claiming that they had made Breivik “suicidal” and depressed.

Citing another article of the Convention on Human Rights that guarantees the right to correspondence, Breivik has also asked for an easing of restrictions on his incoming and outgoing letters.

In 2016, Breivik sued the Norwegian state on the same grounds, with a lower court ruling in his favour before higher courts found in the state’s favour. In 2018, the European Court of Human Rights dismissed his case as “inadmissible”.