Marius Borg Høiby, son of Norway's crown princess, released after a week in custody over rape allegations

The eldest son of Norwegian Crown Princess Mette-Marit was released from custody on Wednesday after his arrest last week on rape allegations, his lawyer said.

Marius Borg Høiby, 27, is the stepson of the heir to the Norwegian throne, Crown Prince Haakon, and the son of Mette-Marit from a previous relationship. He has no royal title or official duties.

Borg Høiby was arrested last week in Oslo on a preliminary charge of having had "sexual intercourse with someone who is unconscious or for other reasons unable to resist the act," police said.

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In Norway, a preliminary charge comes before a formal charge and allows authorities to detain suspects during an investigation.

At the time, the authorities did not say when the alleged rape occurred. Norwegian media reported that Borg Høiby denied the accusation.

Prosecutor Andreas Kruszewski said on Wednesday that police had reviewed the evidence seized in connection with Borg Høiby's arrest and had conducted witness interviews.

Oslo police said in a statement that the decision was taken not to seek the further detention of Borg Høiby.

"As of now, we can no longer see that there is a risk of evidence being tampered with," it said.

The statement added that a police investigation has been launched into "a further matter relating to sexual offenses," without giving details of that case.

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Øyvind Bratlien, Høiby’s defense attorney, said his client's release was "not surprising".

"He shouldn’t have been imprisoned at all," Bratlien told broadcaster NRK.

He later confirmed to Norwegian news agency NTB that his client had been released.

The royal palace had no comment regarding the allegations against Borg Høiby, NTB said.

The arrest, and release, of Høiby is the latest development following an earlier incident which saw him taken into police custody.

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Høiby was first arrested on August 4 and charged with causing bodily harm and damaging property during an first arrested on August 4 inside her Oslo apartment.

About 10 days later he admitted to the allegations and apologised to the royal family in a statement.

Høiby was served with a restraining order, which expires in March next year.

He was arrested again on Friday September 13 after allegedly violating a restraining order and contacting a former girlfriend he admitted assaulting.

Charges against Høiby were then expanded to include the alleged domestic abuse of two former girlfriends, Juliane Snekkestad and Nora Haukland.

The 27-year-old is now facing six years in prison after being accused of making threats against four women.

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In total, the charges relate to his most recent ex-girlfriend involved in the August 4 attack, Snekkestad, Haukland and threats against a fourth person who has not been named.

Borg Høiby lives with the royal couple and their two children, Princess Ingrid Alexandra and Prince Sverre Magnus.

He was officially recognised as a member of the royal family by King Harald before his mother married Norway's Crown Prince but never received a royal title.

Norway’s future queen made headlines in 2001 when she married Haakon because she was a single mother whose previous companion had been convicted on drug charges.

If you or someone you know is impacted by sexual assault, call 1800RESPECT on 1800 737 732 or visit their website. In an emergency, call 000.