The son of Norway's Crown Princess, Marius Borg Høiby, was denied release from prison due to his mother's worsening health. A Norwegian court of appeals rejected his request for freedom after a lower court on Monday ordered his release, pending this coming Monday’s verdict on 40 criminal charges, the BBC reports.

He was on trial earlier this year for a total of 40 charges, including allegations of raping four women as well as domestic abuse and other crimes. He has pleaded not guilty to the four charges of rape. However, he pleaded guilty to several driving offences, to an aggravated drugs offence and breaking a restraining order, and “partly” to threats and aggravated assault.

The request comes after the news that his mother, Crown Princess Mette-Marit, will undergo a lung transplant ”as soon as possible”, as her chronic pulmonary fibrosis diagnosis continues to worsen.

Høiby's defence attorney, Ellen Holager Andenas, told Norwegian news outlet NRK that they have made the request for his release from custody as his mother's health worsens.

His stepsister, Princess Ingrid Alexandra, flew back from Australia this week, where she is a student at the University of Sydney, to be with her mother.

Ms Andenas told NRK: "We have asked the police to do it, and if the police don't do it, we will have to go to court. I find it hard to believe that they won't seriously consider it now."

The Crown Princess's son, who was born from a previous relationship, has been in custody since his trial concluded on February 1.

Last month, he requested to be released from custody to live at his stepfather's official residence, Skaugum, while wearing an ankle monitor.

However, the Oslo District Court refused his request, citing a high risk of reoffending, and he has remained at Oslo Prison ever since his trial ended.

A district court said last Monday that he should be freed from custody.

The 29-year-old told the court: “Sitting inside when I know mum is so sick is unbearable.”

Repeated attempts by his lawyers to secure his release failed until a district court said on Monday he should be freed from custody.

"Sitting inside when I know Mum is so sick is unbearable," Høiby had told the district court.

The BBC claimed that the district court ruled that while there was a “marginal risk” of the crown princess’s son reoffending, it would be “disproportionately intrusive” to keep him in jail.

On Wednesday, the court of appeal rejected the assessment and argued that the risk of reoffending was “virtually unchanged”.

Ms Andenas told Norwegian media: “We are very, very disappointed on behalf of our client. One can imagine how he feels.”

Marius Borg Høiby's trial has concluded, and a verdict is expected on June 15.