This would be an insult to Breivik, who, in a reversal of usual positions, wants to be found sane.
Prosecutors asked a Norwegian court on Thursday to declare far- right mass murderer Anders Behring Breivik insane and commit him to a mental institution.
While not certain that Breivik was not responsible for his actions, they chose to give him the benefit of the doubt in the face of conflicting psychiatric reports, and so to go against the view of most Norwegians that he should go to prison.
"In our opinion, it's worse to send a psychotic person to preventive detention than to send a non-psychotic person to mandatory care," prosecutor Svein Holden told the court.
"We are not convinced that Anders Behring Breivik is legally insane, but we are in doubt. So our petition is for a judgment that he shall be transferred to compulsory mental health care."
Breivik admits to killing 77 people in twin attacks last July, most of them teenagers at a Labour Party summer camp.Breivik's desire to be found sane but acquitted of the murders seems to be a strong indication of insanity.
He says he should be declared sane, but acquitted on grounds that he was defending the Norwegian people by fighting the supporters of Muslim immigration.
If the court finds him to have been insane, he has said that it will be "worse than death", and he will appeal.