Hjort Kraby said Breivik walked along the same route that he took and was encouraged to explain exactly what happened with minimum interruption.
"He has been questioned for about 50 hours on this and he has always been calm, detailed and collaborative. This was also the case on Utoya," Hjort Kraby said.
Police said Breivik was filmed as he described the events. The material is expected to be used as evidence at his trial next year.
Geir Lippestad, Breivik's lawyer, said yesterday his client had been able to recall in detail each shot he fired and every person he killed on July 23 with the assortment of high-powered rifles and automatic weapons he had taken to the island.
Surgeons who operated on many of Breivik's wounded victims said he had clearly wanted to kill and had aimed to hit the upper parts of their bodies.
Breivik's car-bomb attack on the centre of Oslo and his subsequent massacre on Utoya Island killed 77 people. Sixty-nine of his victims were youth members of Norway's ruling Labour Party, which Breivik said he wanted to punish for embracing multiculturalism.
He told police during questioning that he believed the killing was necessary to save Norway and Europe from "Muslim domination".
Police confirmed yesterday that Breivik had called them several times during the attacks in what appeared to be an attempt to give himself up.
Lippestad has said his client is probably insane. But police psychiatrists have said Breivik appeared to be fully in control and aware of his actions during both attacks and that the courts would be unlikely to accept a plea of insanity.
If convicted, Breivik would face a maximum 21-year jail sentence. However, under Norwegian law, he could remain in custody indefinitely after serving his sentence, if still considered a danger to the public.
- INDEPENDENT