CCTV footage pic of youth in relation to man stabbed in unprovoked attack in Belconnen.

Police released a CCTV image of the alleged offender at the Belconnen bus interchange at the time. Photo: Supplied / ACT Policing

A Canberra teen with a "capacity for mindless violence" while drunk has been sentenced to seven years for stabbing three men in vicious, unprovoked attacks.

The crimes put one young man on an operating table with a punctured stomach lining and left another fighting for his life with as many as 15 stab wounds.

The now-18-year-old offender, a Sudanese national born in a Kenyan refugee camp, will be behind bars until January 2015.

He has already spent 17 months locked up at the Bimberi Youth Justice Centre for crimes committed in the weeks either side of his 17th birthday.

Justice John Burns this morning said the crimes were so serious they warranted a term of imprisonment.

The teen, who cannot be named because he was a child at the time, accosted two teens at the Belconnen bus interchange in the early hours of April 2 last year.

The ACT Supreme Court heard he approached the two and said, "what the f*** did you say to me," to which they denied saying anything.

The boy stabbed one man twice in the stomach and, when the other intervened, stabbed him in the arm.

The pair ran towards an underground car park with the knife-wielding teen in pursuit.

One of the victims tried to take a photo of their assailant on his phone but dropped the device.

The victims got the attention of passing motorists and the attacker fled, taking the mobile phone.

One of the victims suffered deep stab wounds to his stomach, puncturing the lining and requiring surgery.

Hours earlier the same assailant threatened two youths at John Knight Memorial Park, holding a knife to one man's throat and striking the other with the flat of the blade.

Police arrested the youth, then aged 16, but released him on bail.

He told them he acted in self-defence at the bus stop, but Justice Burns today rejected that claim.

The youth was still on bail on June 1 when he was involved in another incident the judge described as "unprovoked and premeditated".

"It was also marked by a singular viciousness of execution," Justice Burns said.

The youth and three others lured 18-year-old Tayler Hazell to a Scullin flat under the pretenses of getting drunk.

They trapped their victim in a bedroom where the youth, armed with a flick knife, was waiting wearing plastic gloves.

The Crown argued the boy stabbed Mr Hazell 15 times, but the defence maintained it was closer to seven.

The judge said the boy's version was likely an understatement but the true number of stab wounds, while difficult to ascertain, was not particularly significant.

"You inflicted grievous injury on Mr Hazell, the physical consequences of which will be with him for the rest of his life, and the psychological consequences of which are likely to be with him for some time," Justice Burns said.

The assault continued as a co-offender held the door from the outside, stopping the victim from escaping the bedroom.

The seriously injured man finally got free and crossed the road to a supermarket, where he called for help before collapsing to the ground.

"The night I got stabbed was easily the worst night of my life, I will not forget it," Mr Hazell said in a victim impact statement.

"The scars I have will never go away, I just want my confidence back.

"I believe I'm lucky to be alive."

The youth eventually pleaded guilty to two counts of intentionally wounding, stealing the mobile phone and intentionally inflicting grievous bodily harm on Mr Hazell.

The judge also took into account two assault charges stemming from the memorial park incident.

The court heard the youth's upbringing in conflict-ravaged Africa was traumatic but did not leave him with post-traumatic stress disorder.

At the time of the first offence the boy had consumed about 20 standard drinks, and the author of a pre-sentence report said he demonstrated "a capacity for mindless violence when intoxicated".

He was assessed as a moderate risk of reoffending.

Justice John Burns took the man's age, lack of prior convictions, pleas of guilty, supportive family and positive life changes while in custody into account in his favour.

He imposed a seven-year sentence backdated to June 2011.

But the sentence will be suspended in January 2015 and the youth will enter a four-year good-behaviour order with conditions to steer clear of drugs and alcohol.

By the time he is release he will be 20 years old.