The boys were 16 years old when they committed the murder in early December last year.
By consensus, they forced alcohol on their victim of the same age, and then subjected him to brutal violence and abusive treatment for several hours in various places in northern Helsinki.
They kicked and hit him on the head and used the blow, which they also filmed.
The seriously injured boy was then left unconscious on the ground in the cold.
When he was found by a construction worker three days later, he was dead.
The damages were counted at more than 100.
Intention to kill?
The prosecution has described the violence as sadistic, but when the sentences were to be imposed, the question was whether they intended to kill the boy.
A psychologist has claimed that they understood the consequences of their actions, which the Helsinki District Court also assesses.
The violence was planned in advance, described as systematic and afterwards they shared recordings with each other.
A boy is sentenced to prison for just over ten years, one to just over nine years and one to just over eight years, several Finnish media report.
The prosecution had demanded a slightly longer prison sentence for all three.
They themselves denied murder - two of them instead admitted aggravated assault and aggravated manslaughter, while the third only admitted assault.
More crimes over time
In addition to the murder, the three boys are convicted of having abused and robbed the same boy on previous occasions in 2020.
All the boys involved were born in 2004 and were therefore sentenced according to a slightly lighter penalty scale. For murder, people between the ages of 15 and 20 can be sentenced to a maximum of 12 years in prison, but when the other sentences are added, the three boys risked up to 15 years in prison. Given their young age, they probably only need to be locked up for about a third of their sentence.