At the start of his trial in Oslo, Breivik made a far-right salute and said he did not recognise the legitimacy of the court.
He pleaded not guilty to charges of terrorism and murder, but said he "acknowledges the acts" and that he killed 77 people last July in "self-defence".
During proceedings the 33-year-old smirked as the prosecution spoke about his early online gaming habits and bomb-making plans - but was tearful as the court was shown the 12-minute video he posted online before the terror attacks.
Breivik made a far-right salute at the start of his trial in Oslo
A lip-reading expert for Norwegian broadcaster TV2 said Breivik told his lawyer: "I am OK. It is just an emotional film."
Defence lawyer Geir Lippestad later said while the court must considered Breivik's mental state at the time of the crime, it was the defendant's wish to be sentenced as legally sane.
As a result, Mr Lippestad said his case would support this choice.
Breivik has admitted detonating a bomb in the centre of Oslo and opening fire on young people attending a summer camp on Utoya island nearly nine months ago.
He believes the attacks were a political act designed to prevent what he described as an Islamic invasion of Norway.