Profile of self-confessed mass killer Anders Behring Breivik

As the trial approaches, much has been written about Breivik's childhood in national and international media in an attempt to understand what turned the seemingly shy boy into a killer.

For many Norwegians, the fact Breivik looked and acted so normally was one of the most disturbing aspects of the attacks.

Breivik was born in Oslo on February 13, 1979. He grew up with his mother and had sporadic contact with his diplomat father after his parents divorced.

Despite being brought up in a wealthy part of Oslo, there was never much money in the single-parent's household.

Crime researchers speculate Breivik may have struggled to cope with the absence of a high-achieving diplomat father -- Jens -- who abandoned the family when his son was only a one-year-old.

Jens and his new wife -- another career diplomat -- briefly sued for custody of the young Anders, but lost the case. Breivik occasionally visited them in France, but grew up with his mother, a nurse, and her new husband, a Norwegian army officer.

Daily "Dagbladet" journalist Tor Arne Andreassen has written a lot about Breivik's early life. He said growing up in a poorer household among wealthier ones had possibly imposed a kind of inferiority complex on him.

When Breivik was four-years-old the family first came into contact with psychiatric services and he was put under observation.

Andreassen said the psychologist recommended Breivik be put into foster care.

"This psychologist, he wrote a couple of reports about some disturbing finds that he made. He found that the living conditions were very unstable for the kid and he recommended that he should be put into foster care," Andreassen told Reuters.

But this never happened.

In his 1,518-page "manifesto", posted on the Internet and e-mailed to hundreds of contacts a few hours before the attacks, Breivik wrote he had not had "any negative experiences in my childhood in any way", but his lawyer said Breivik told them he had very few memories of his early childhood.

"Breivik himself says he remembers little of the period and has little memory of the fact there has been psychologists involved," Breivik's lawyer Vibeke Hein Baera said.

"What he says about this himself is that he is working on keeping his feelings under control. He sees himself as a soldier -- a warrior in war," she added.

Breivik had said he committed the attacks on July 22 last year to protect Norway from multiculturalism and saw himself as a crusader.

"What is clear is Breivik sees the world in a way few people do. He thinks we are at war. He's got a vision for -- what you could call -- a new world order that few people can associate with," his other lawyer, Geir Lippestad said.

Most of those close to Breivik have gone underground since the attacks of July 22 and have refused to talk to media.

Andreassen is one of the few people who has spoken at length to Breivik's friends.

"It seems from what we've been hearing that he was a quiet child who actually hid a bit behind his sister when he was a very small child. Later, when he was in his teens, he was also described as a quiet boy," he said.

Andreassen said many were "astonished" to find out Breivik was the perpetrator behind the two attacks.

"This vicious, murderous side of him came out, of course when he came to the island and murdered 69 people out on that island. That side of him was something which really surprised everyone that we've talked to whose seen him in his youth or early adulthood," he said.

"In his early twenties he was convinced that he actually had a superior mind and that he would be able to do just about anything better than anyone else," Andreassen added.

Breivik's trial starts on April 16 and will last 10 weeks. The verdict is expected on July 20 at the latest.

If his judges rule at the end of the trial he is psychotic, he is likely to be to placed in a high-security psychiatric unit. If not, he would face up to 21 years in prison, but could be held longer if deemed too dangerous to be released.