"I think that all of Norway has seen I am not irrational," the 33-year-old right-wing extremist said on the eighth day of his trial, adding: "So I am not worried anymore" about being sent to a psychiatric institution.
Breivik, who has been charged with "acts of terror", is seeking to convince an Oslo court that he is sane so that his anti-Islam ideology will be taken seriously and not considered the ravings of a lunatic.
A first psychiatric evaluation last year concluded he was suffering from paranoid schizophrenia, but a second opinion found him of sound mind, and it will ultimately be up to the judges to determine the question of his sanity when they hand down their verdict in July.
If the court finds him sane, Breivik will face Norway's maximum 21-year prison sentence, but that term can be extended for as long as he is considered a threat to society.
If he is found criminally insane however, he will be sent to a closed psychiatric care unit for treatment -- a fate he has described as "worse than death".
"For a political activist, the worst thing that can happen is to land in a mad house because that would delegitimize everything one believes in," he explained.
Psychiatrists Synne Sørheim and Torgeir Husby were appointed by the Oslo district court to carry out the first evaluation of Breivik, and they concluded in November he was psychotic.
On Wednesday, he challenged the diagnosis, which he has claimed contains "more than 200 lies" and has called "the ultimate humiliation."
"These are ill-willed fabrications," Breivik told the court on Wednesday, referring to passages from the report.
He later added: "They may not be ill-willed, but they are in any case wrong."
The two experts drew their conclusion "very early" and aimed the rest of their work at proving their diagnosis was correct, he said.
"You cannot understand that a normal person could do something like this," Breivik said, addressing the two experts sitting before him, insisting they "were emotionally affected (by the attacks) and they were not competent to evaluate a person responsible for political violence."
"If I had read a description of the person they describe, I would have agreed: this person needs psychiatric care," he said, adding: "But the person described in this report is not me."
Breivik said he had received a letter from a Swedish militant nationalist who described his own treatment in a psychiatric ward as "a chemical lobotomy."
"He says it's awful. He sits at a table drooling," he said.
On July 22nd, Breivik first set off a bomb near government offices in Oslo, killing eight people, before going to nearby Utøya island where he killed 69 people, mostly teens, attending a Labour Party youth camp.
Sørheim and Husby's diagnosis last year caused an uproar in Norway, where many were astounded that the man who methodically planned his attacks for years and then executed them with precision could be found not responsible for his actions.
The court therefore ordered a second opinion by two other experts, Terje Tørrissen and Agnar Aspaas, who concluded earlier this month that Breivik was sane.
Their evaluation, which a commission found to have some weaknesses, concluded that the confessed killer was "narcissistic" and "asocial" but not psychotic.
"I don't agree with any of these diagnoses," Breivik told the court on Wednesday.
Regarding the question of whether he was asocial, Breivik said: "It is impossible to avoid this diagnosis when you are the perpetrator of politically motivated violence because you have declared war on the establishment."
He added though that he liked to socialize and considered himself a "fun" person.
He also insisted he was not a narcissist, since "a person who is ready to give his life for a cause and for others does not place himself over all else."
Earlier this week, he lamented in court that his sanity was being questioned at all, claiming to be the victim of "clear racism".
"If I had been a bearded Jihadi ... there would not be a need for a psychiatric evaluation," he said.
Breivik, who has confessed to carrying out the twin attacks but refuses to plead guilty, has said his attacks were "cruel but necessary" to stop the ruling Labour Party's "multicultural experiment" and the "Muslim invasion" of Norway and Europe.