Mette-Marit, who chose bold outfits for the garden party and the concert, made no comment about the ongoing case, and the press present were not given any opportunity to ask questions.
Last week, it was confirmed that Marius, 28, has been charged with 32 offences, including four counts of rape. Although he denies the most serious accusations against him, he plans to plead guilty to some lesser charges in court when the trial starts, his lawyer Petar Sekulic told Reuters.
EURO ROYAL NEWS
A trial is expected to take place in January, and if he is found guilty of the most serious charges, Marius could face up to ten years in prison.
The Norwegian royal court said last week: "It is for the courts to consider this matter and reach a decision. We have no further comment."
Marius is Crown Princess Mette-Marit's eldest son from a previous relationship. He is not included in the line of succession. Mette-Marit shares two children - Princess Ingrid Alexandra, 21, and Prince Sverre Magnus, 19 - with Haakon.
Queen Sonja attended the daytime garden party with Crown Prince Haakon and Crown Princess Mette-Marit, who sported a rainbow-patterned jacket, cream wide-legged trousers and trainers.
Later, the Norwegian royals were present for an open-air concert in the grounds of the Castle.
Crown Prince Haakon held hands with his wife as they arrived at the event, with Crown Princess Mette-Marit opting for a brightly-coloured patterned coat for the occasion.
The couple quietly marked their 24th wedding anniversary on Monday.
The royals watched the festivities from a box, with Queen Sonja standing out in a red collared coat.
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