I don't know about Norway, but a verdict hasn't been handed down and he broke his custody terms before trial and ended up being jailed. If he's found guilty, in the US, he wouldn't be anywhere eligible for a work release of any kind. He would be a convicted violent felon. They aren't chosen for work release or...very, very rarely.
Marius is using his concern for his mother as a ruse to get out, I'll bet he's want to do a runner. He's violent and cruel to women, but he's a scared coward about prison, there's always someone bigger, meaner and more violent than you in prison. He may not be segregated in prison and he may not have his mother looking out for him. All these crimes he's committed were carried out after his mother's diagnosis, he didn't give a care about her. Marius only turned to his mother when he was arrested.
As for MM, she aided and abetted her son. I'm sure she was far from truthful when questioned by the police and probably made sure they knew about her medical condition...and her status as Crown Princess.
I'm harsh, I know, but it's the truth. We used to get inmates at the two hospitals I worked at and they are the biggest con artists in the world and their mothers are just as bad for the most part. Marius is only going to serve 7 yr. maximum if found guilty, if he doesn't die in prison....