Richard Nieuwenhuizen's death shocked the football-crazy Netherlands and prompted soul-searching about the parenting of young athletes, as well as about violence in the sport.
The hearing in Lelystad, Netherlands, is mostly closed to the media due to the young age of most of the suspects. It began with testimony from four different forensic experts debating the exact cause of Nieuwenhuizen's death.
The fatal incident took place on Dec. 2 in the northern Dutch city of Almere, after the home team Buitenboys drew 2-2 against the visiting Nieuw Sloten, which is based in a mostly immigrant neighbourhood of Amsterdam.
Nieuw Sloten players confronted Nieuwenhuizen after the match. What happened next is not clear. Nieuwenhuizen was photographed lying on the ground shortly afterward. Eyewitnesses said he was kicked and punched in the head and neck.
He initially seemed to recover and shrugged off questions about whether he would file a complaint, but he later collapsed and died in hospital the following day.
The Netherlands' National Forensics Institute concluded he was killed as a result of injuries sustained during the attack.
Each of the defendants has his own lawyer. They are expected to argue that Nieuwenhuizen, who was 41, had an underlying condition that contributed to his death or caused it.
Gerard Spong, one of the Netherlands' most prominent criminal defence attorneys, summoned British forensics expert Christopher Milroy to testify that Nieuwenhuizen may have suffered from a rare genetic condition that weakened his aorta.
Dutch expert Bela Kubat said there was no evidence for that, and that damage to Nieuwenhuizen's aorta was explained by his injuries.
The seven youths were all minors when the incident took place and are not identified in court documents, though their first names have been circulated widely in local media.
All the suspects say they are innocent of wrongdoing. Only one of them has acknowledged having touched Nieuwenhuizen, and he said he may have kicked at his shoulder.
If convicted, the youths could face a maximum of two years in prison.
The adult suspect, the 51-year-old father of one of the minors, is identified as El-Hasan D under Dutch privacy laws. He faces a maximum sentence of 15 years if convicted of the most serious possible charge, voluntary manslaughter.
Nieuwenhuizen is survived by his wife, Sandra, and his son, Alain, who was playing in the match.
After Nieuwenhuizen's death there was outrage in the Dutch football world, with many noting that in recent years referees, linesmen and even fans have been attacked by young players.
"You can't imagine it happening," said Ajax coach Frank de Boer. "That boys of 15, 16 years short circuit like that. You wonder about the parenting."
More than 12,000 people attended a silent march for Nieuwenhuizen in Almere on Dec. 9.
"What can I do to teach today's football youth the difference between anger and aggression?" said national football association chairman Michael van Praag at a ceremony afterwards. "Football is emotion, but it's also winning and losing. You have to be able to do both, otherwise you don't fit in our sport."
The trial is due to run five days, with 60 witnesses scheduled to testify. A ruling is likely in late June.