Dwayne Michael Byrne must spend a minimum nine years in jail for stabbing Steen Locke six times on St Kilda's Brooks Jetty on the night of February 7 last year.

Mr Locke and a friend were seated on the jetty when they turned their heads towards Byrne and a woman who appeared to be arguing, Supreme Court Justice John Dixon said on Wednesday.

Byrne yelled to Mr Locke: "What the f--- are you looking at?" Seconds later, he attacked Mr Locke from behind and stabbed him in the back of the head, in both shoulders and to the torso.

"[Mr Locke] was disadvantaged by the way he was sitting when this cowardly attack took place," Justice Dixon told Byrne.

"But once he got to his feet you ran off. You left the knife embedded in Mr Locke's back."

Byrne, 23, was this year found guilty of attempted murder. He also pleaded guilty to being a prohibited person in possession of a weapon, after police found a pen pistol at his home.

Mr Locke suffered life-threatening injuries and lost lots of blood, the court heard. Justice Dixon said it was only good fortune he survived. The jurors' verdict, the judge said, showed they believed Byrne intended to kill.

"What you should have done was to have walked away, but you did not do so," Justice Dixon told him.

"Rather, as the jury has found, you formed a murderous intention, and acted upon it using the knife that you happened to be carrying. In something of a frenzy, you stabbed your victim multiple times."

Byrne's denial he was at the jetty meant the matter went to trial, and Justice Dixon said Mr Locke had relived his ordeal giving evidence, and had been upset seeing Byrne's "smirking gaze".

Justice Dixon said the reasons behind Byrne's offending were never explained, though he had been drinking alcohol beforehand and using the drug ice in between a previous prison stint and the night on the jetty.

Byrne endured a troubled childhood and lived on the streets at age 11, the court heard, began abusing drugs and alcohol and became a father at 15.

His case worker reported Byrne was motivated to rehabilitate himself for his daughters' sake, but Justice Dixon said the young man's long criminal history - for dishonesty, weapons, violence and driving offences - and his substance abuse and poor behaviour in prison gave him little prospect of a successful reintegration into the community.

Protecting the community was paramount, Justice Dixon said.

"Our society will not tolerate random, unprovoked attacks on innocent citizens by offenders with poor impulse control and wandering the streets armed with a knife," he said.

"The community cries out for protection."

Byrne has already served almost 600 days in custody.