Anders Behring Breivik has admitted to killing eight people when he exploded a truck bomb outside government offices in Oslo and then shooting dead 69 people at a youth camp on Utoya island nearby.
The 32-year-old right-wing extremist denies criminal guilt because he believes the massacre was necessary to save Norway and Europe.
If found guilty on terrorism charges he faces 21 years in prison.
Meanwhile, survivors and families of victims are due to visit Utoya later Friday.
