An expert in far right ideology says the political views of mass killer Anders Breivik should not be seen as signs of insanity.
Initially psychiatrists said Breivik was insane, but the trial in Olso, Norway, must definitively rule on his mental state to decide whether he will go to prison or into psychiatric care.
Breivik, 33, admits the attacks in Oslo and on the island of Utoeya, in which 77 people died and 242 were wounded on 22 July last year.
The BBC reports the trial is seeking to establish whether he is sane, in which case he will be sent to prison. If not, he will be held in a psychiatric institution.
Breivik denies criminal responsibility, arguing his attacks were necessary to combat multiculturalism and prevent a "Muslim invasion" of Norway and Europe.
On Wednesday, police said they were confident that Breivik had acted on his own and that they had found no evidence he belonged to a Europe-wide anti-Muslim network.
Holocaust historian Terje Emberland told the court on Thursday that Breivik's views could be described as "fascistic" and that some people shared his ideas.
His "distorted world view" had allowed him to "elevate himself above the law and consider his terrorist activities as a legitimate resistance, a fight", he suggested.
Asked by a prosecutor when extremism could descend into madness, Mr Emberland said: "That is an extremely complex question."