( CNN ) -- Anders Behring Breivik , accused of killing of 77 people in a bomb and gun rampage in Norway last summer , was formally charged Wednesday with committing acts of terror and voluntary homicide , prosecutors said . Prosecutors say he was psychotic at the time of the killings and should be transferred to `` compulsory mental health care . '' A fierce debate has raged over whether Breivik is mentally competent to face criminal punishment . The mass killing on July 22 was the single largest loss of life in Norway since World War II . Breivik is accused of killing eight people in a bomb attack in Oslo , then going to Utoya island outside the city and systematically gunning down 69 more people , many of them teens and young adults . Breivik has pleaded not guilty , though he has admitted carried out the attacks , the judge handling his case said previously . His trial is due to start April 16 and is expected to last 10 weeks . Read the full indictment . The court case is designed to demonstrate his guilt or innocence . His punishment , if he is found guilty , will then be based on the determination of his sanity . Last month , a court ordered him to undergo a fresh round of psychiatric evaluation as experts seek to determine his mental state ahead of a trial . Two court-appointed psychiatric experts recommended that he spend four weeks under 24-hour psychiatric monitoring so the court can get the fullest possible picture of his behavior , court documents released February 10 said . The two experts were appointed to evaluate his mental state after the court requested a second opinion because of the importance of the question of sanity to Breivik 's trial . In November , prosecutors said psychiatrists had determined Breivik was paranoid and schizophrenic at the time of the attacks and during 13 interviews experts conducted with him afterward . It may not be possible for him to be sentenced to the maximum punishment for the crimes if he 's deemed insane . Breivik reiterated some of his extremist views during a hearing last month , which began with him entering with a smile and offering up a raised , clenched-fist salute . He insists nobody could believe that he was insane , and describes questions about his mental condition as ridiculous , his lawyer , Geir Lippestad , told the court . Breivik claims the shooting rampage was a matter of self-defense , meant to save Norway from being taken over by multicultural forces and to prevent ethnic cleansing of Norwegians , Lippestad said . Authorities have described him as a right-wing Christian extremist . A 1,500-page manifesto attributed to Breivik posted on the Internet is critical of Muslim immigration and European liberalism , including Norway 's Labour Party . The victims on Utoya Island were among 700 mostly young people attending a Labour Party camp on Utoya island . Journalist Olav Mellingsaeter in Oslo and CNN 's Laura Perez Maestro contributed to this report .
Anders Behring Breivik is accused of killing 77 people last summer . Prosecutors say he is psychotic and should be hospitalized . There has been a fierce debate over his sanity , which will affect his punishment . Breivik admits the killings but pleads not guilty , a judge has said .