That was the grim assessment of the clinical psychologist in a juvenile justice report relating to one of the teenagers involved in Mr Leicester's death.

Supreme Court Justice Peter Hall described the incident last Friday as completely unprovoked and involving an extremely high level of violence and a willingness to injure.

Justice Hall made the remarks, including quoting the juvenile justice report, during the manslaughter sentencing of three teenagers, who can only be identified as GDP, PB and CW for legal reasons. GDP and PB, pleaded guilty to Mr Leicester's manslaughter in June.

CW pleaded not guilty to murder or manslaughter but was found guilty of the lesser offence by a jury in July.

GDP was sentenced to five years jail, with three years parole, after his release in November, 2012. PB, who began the verbal altercation that led to the bashing but did not strike Mr Leicester, was sentenced to three years jail with a parole period of three years after his release next November.

CW was sentenced to six years jail, with three years parole, after his release in November, 2013.

Mr Leicester died from a tear to the artery supplying blood to his brain after being attacked by the trio.

He was on his way to a party about 11.30pm on November 21, 2007, when he was confronted by PB and GDP, who wrongly believing Mr Leicester had earlier yelled insults at them.

GDP punched Mr Leicester in the jaw and kicked him as he lay on the ground. CW, who arrived at the scene shortly afterwards, delivered three kicks to Mr Leicester's head. An autopsy found any one of the kicks or punch could have caused the injury that led to Mr Leicester's death the next day in St George Hospital.

Justice Hall said he was bound to make the sentences a deterrent to other young people in light of the senseless violence committed on a stranger in a public place.