The son of Norway's crown princess is standing trial on charges of rape, domestic violence, assault and drug possession, among other crimes, in a case that has shaken the embattled royal family.
Marius Borg Hoiby, 29, son of Crown Princess Mette-Marit and stepson to Crown Prince Haakon, could face multiple years in prison if found guilty of the most serious of the 38 charges brought against him.
He pleaded not guilty to four counts of rape as the proceedings got under way.
Lead prosecutor Sturla Henriksboe said Mr Hoiby would be treated like any other Norwegian citizen. "He (Marius) will not be handled tougher or milder because he is part of this family," Mr Henriksboe said in his opening statement.
Mr Hoiby's lawyer, Petar Sekulic, earlier told Reuters his client did not admit criminal guilt for the charges of rape or domestic violence, but did admit guilt for some of the less serious matters.
"He will give a detailed explanation about this in court,"Mr Sekulic said.
The case is scheduled to run until 19 March. Mr Hoiby is due to testify tomorrow.
On Sunday, Norwegian police detained him on suspicion of causing bodily harm, wielding a knife and violating a restraining order. A court ruled yesterday that he could beheld in custody for four weeks. His lawyer told Reuters he was considering an appeal.
The court case is the most serious crisis to hit the Norwegian royal family in peacetime, according to historian Trond Noren Isaksen, though Mr Hoiby does not have a royal title and is outside the line of succession.
The start of the trial also comes days after his mother Crown Princess Mette-Marit apologised for her "poor judgement" for maintaining contacts with the late US sex offender Jeffrey Epstein after he was convicted of child sex crimes in 2008.
Crown Prince Haakon and Crown Princess Mette-Marit are not planning to attend court proceedings, Prince Haakon said in a statement, adding he trusted the justice system to be fair and proper.
About Mr Hoiby, the Crown Prince said: "We love him. He is an important part of our family. He is a Norwegian citizen, so he has the same responsibilities as everyone else, as well as the same rights."
He expressed sympathy for the alleged victims. "We think about them, we know many are going through a difficult time," he said.
The Nordic country is a constitutional monarchy in which the king is the formal head of state while political power rests with parliament and the government.
Some 70% of Norwegians support the monarchy as an institution, according to a Norstat poll for public broadcaster NRK conducted in January among 1,030 people and published on Friday. Only 19% want another form of government.
