The trial, which started on Tuesday morning, is the biggest ever honour-related case in Sweden.
On April 4 last year, the 23-year old man was kidnapped from a central square in Gävle, where he was forced into a car. Two weeks later he was found dead in a small town south of Sundsvall, believed to have been strangled with a noose.
Six of the people now on trial are suspected of kidnapping and murder, the remaining three are charged with complicity in the crimes. They are all from the area around Sundsvall, in the Västernorrland county.
The prosecutor believes the murder was revenge following an affair between the 23-year-old and a married woman, which started in 2015. The woman divorced her husband, but a few months later, she also terminated the relationship with the new boyfriend. He then started a Facebook account that included a picture of the former girlfriend kissing him on his cheek.
"He started a Facebook account and sent friend requests to people in the woman's family and the ex-husband's family," prosecutor Elisabeth Hermanrud told Swedish Radio News.
But what makes this a case about honour, and not just plain jealousy?
"I don't think the reaction would have been this strong, if it had not been honour-related," said Elisabeth Hermanrud.
Among those on trial is the former girlfriend of the murdered man, who is suspected of luring the 23-year-old to a square in Gävle where he was abducted. Her former husband and her two older brothers are among those suspected of the murder itself.
All of the accused deny the charges. The trial is expected to go on for 28 days.