While a coroner was wrapping up the autopsy reports on the victims of Breivik's July shooting massacre on Utøya island, a man suddenly got up and threw a black shoe at the right-wing extremist seated just a few metres away from him.
The shoe attack was followed by applause, "bravos" and tears among the many survivors and victims' family members seated in the courtroom, and led to a brief suspension of proceedings on the 17th day of the trial.
The shoe did not hit Breivik but landed on one of his lawyers, Vibeke Hein Baera, who was sitting between the accused and the onlookers.
"Luckily, it was just a shoe," Hein Baera told AFP after the incident.
The attacker, a man of Iraqi origin whose brother was one of the 69 people Breivik shot dead on Utøya on July 22, was quickly brought under control by security guards and escorted out of the courtroom as he continued to shout in English, through tears of anger, "Go to hell!"
The episode recalled a similar attack on former US president George W. Bush, who during a visit to Baghdad in December 2008 was the target of a shoe-throwing Iraqi journalist.
When the proceedings resumed a few minutes later, Breivik addressed the onlookers.
"If someone wants to throw something at me, do it at me while I'm entering or leaving, and not at my lawyer," he said.
The shoe attack was the first serious incident since the beginning of the 33-year-old right-wing extremist's trial on April 16th, and marked the first time any of the onlookers have addressed Breivik directly.
Before suspending the proceedings again for lunch, head judge Wenche Elizabeth Arntzen thanked the participants, including relatives who throughout the trial have often cried quietly or held each other for comfort, for the dignity they had shown.
"I would like to thank all of those who have contributed to enabling this particularly difficult procedure to be held in a meaningful and respectful manner," she said.
Breivik has been charged with committing terrorist acts on July 22nd when he killed a total of 77 people by first bombing a government building in Oslo before going on his shooting rampage on Utoeya, where the ruling Labour Party's youth wing was hosting a summer camp.
Most of the victims there were still in their teens, the youngest having just celebrated her 14th birthday.
He has confessed to the acts but has refused to plead guilty, insisting his massacres were "cruel but necessary" to stop the Labour Party's "multicultural experiment" and the "Muslim invasion" of Norway and other European countries.
While Breivik will surely be found guilty, his 10-week trial will help determine the tricky question of his sanity and whether he will be sent to prison or to a mental institution.
Two court-ordered evaluations have reached opposing conclusions, and it will be up to the five-judge panel to rule on the issue when they hand down their verdict in mid-July.
Breivik himself is intent upon proving his sanity so that his anti-Islam ideology will not be written off as the ravings of a lunatic.