Speaking on the last day of the high-profile trial, Nilsson argued for maximum four-year terms in a juvenile detention centre for each of the accused.
The prosecutor said that the boys had displayed complete indifference to the fact that there was a serious risk the victim could die from his injuries.
A fifth boy is also in court on charges of incitement to aggravated assault.
A number of witnesses appeared before the court on Monday at the end of a high-security hearing that has taken place entirely behind closed doors.
Riccardo Campgiani died after a row at a private birthday party in Stockholm’s Kungsholmen district on October 6th.
A disagreement between a number of the young party-goers escalated when they left the venue and went out onto the street.
Campogiani and another 16-year-old stood arguing with each other. According to the prosecutor, Campogiani retaliated after being struck. He then ran towards Kungsholms Hamnsplan, where he was knocked to the ground.
A number of the boys who had given chase began kicking Campogiani in the head and upper body.
By the time an ambulance arrived at the scene, Campogiani’s heart had stopped beating. At the hospital, doctors managed to resuscitate him. But they also noted that he had suffered a brain hemorrhage..
He was kept alive with the aid of a respirator but died a day and a half after the attack.
Reports of the brutal assault of Riccardo Campogiani shocked Sweden. A week after the attack more than 10,000 people gathered at Kungsträdgården in central Stockholm in a coordinated protest against street violence.