In the courtroom on Friday, Høiby, son of Norway's Crown Princess Mette-Marit, demonstrated how he held his hands around her neck.
"I know I slapped her," he also said, explaining he thought she had been unfaithful.
He described how he broke things and found a knife that he threw away. When the police arrived at the apartment in Oslo in August 2024, the knife was stuck in the wall. Shortly afterwards, he was arrested for the first time.
This week, the woman testified that Høiby beat her so badly she lost her hearing and that he repeatedly choked her.
The 29-year-old Høiby only partially admits criminal guilt in relation to his ex, saying he does not believe it amounted to gross violence.
Marius Borg Høiby, 29, is the son of Crown Princess Mette-Marit of Norway from a previous relationship with Morten Borg. Mette-Marit married Crown Prince Haakon in 2001.
The "Bonus Prince" is charged with 38 crimes, including assaulting a former girlfriend and four counts of rape. According to prosecutors, the rapes occurred while the victims were asleep.
Høiby has admitted to certain crimes but denied allegations of rape.
The trial began on February 3 and will last at least six weeks. Høiby faces up to 16 years in prison.
