The state had filed an appeal after a district court in Oslo last April concluded the 37-year-old's rights had been violated and he was subjected to "inhumane" and "degrading" treatment in prison, in breach of the European Convention on Human Rights.
In prison, Breivik has a three-cell complex where he can play video games and watch television on two sets. He also has a computer without internet access, gym machines, books and newspapers.
On the first day of the appeals case hearing held in the gymnasium of the Skien prison where he is incarcerated, Breivik, known for provocative antics, arrived in court making a Nazi salute at the media members present, a gesture certain to upset families of the victims and which he also made at the opening of the district court hearing.
The judge immediately reprimanded him. "It's offensive to the dignity of the court and disturbing given what we are here to examine," judge Oystein Hermansen said.
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On July 22, 2011, Breivik, disguised as a policeman, gunned down 69 people, most of them teenagers, at a Labour Party youth camp on the small island of Utoya, tracking them down for more than an hour, where they were trapped by the cold waters of the lake.
Earlier that day, he killed eight people with a bomb he detonated at the foot of government building in Oslo.
It was the bloodiest attack on Norwegian soil since the end of World War II.