Declan was alone walking down a dark street when he was kicked, stomped on and stabbed by a group of eight boys in March 2022.
He had just left a party in Reservoir in Melbourne's north and had become separated from his friends.
In the early hours of March 13, a stolen Mazda pulled up and the group of boys got out and pounced on Declan.
In a two-minute frenzied attack, the group stabbed and kicked him as he lay on the nature strip.
The group got back in the car and drove off, but returned briefly to stomp on him again and remove his shoes, before leaving.
Declan bled to death on the ground after suffering 152 injuries, including 56 stab wounds and 66 blunt force injuries.
Supreme Court Justice Rita Incerti on Friday found four of the attackers - known under the pseudonyms SA, DM, QDM and SY - guilty of Declan's murder.
The boys had gone through a judge-alone trial in December, a couple of months after their 13-year-old co-accused was found to be too young to be held criminally responsible.
Three other members of the group were jailed on September 12 for their roles in the killing.
A 16-year-old boy, who was the second youngest, was jailed for up to 15 years after pleading guilty to murder.
Two 18-year-olds were handed youth detention sentences of three-and-a-half and four years.
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