"That's just part of his nature and how he was - [he was] just a great guy," his widow, Helen Bertocci, said outside the Victorian Supreme Court on Friday.

Mr Bertocci, 46, was fatally stabbed in broad daylight at a busy Altona North intersection, after he pulled over to help Jonathon Sporton's pregnant girlfriend on Blackshaws​ Road on December 14, 2014.

Sporton, 22, was sentenced on Friday to 21 years' jail, with a 17-year non-parole period, for the senseless murder of the Good Samaritan.

Sporton was on bail, and had been abusing ice, when he murdered Mr Bertocci.

Mrs Bertocci thanked police and the Office of Public Prosecutions for their work in bringing the case to resolution.

But, she said, she found little joy in the sentence.

"Nothing brings Roger back, nothing brings him back to being with us," she said.

"I think the sentencing today allows us to breathe that little bit easier, but it's not over; it's not over. For us, it's never over; it doesn't end."

In his sentencing remarks, Justice Christopher Beale outlined Sporton's extensive criminal history dating back to when he was 14.

Sporton's lengthy and violent history included multiple convictions for recklessly causing serious injury, unlawful assaults, armed robbery and weapons offences.

The court was told that 10 days before the stabbing, police had taken Sporton for a psychiatric assessment at the Alfred Hospital, where Sporton spoke of suicidal thoughts, paranoia and admitted to heavy drug use.

He had been seen fighting on a road with another man, and had attempted to run in front of a truck in front of police.

On the day he stabbed Mr Bertocci, Sporton had sent his 22-weeks' pregnant girlfriend - who has since given birth to their daughter and remains in a relationship with him - an aggressive text message accusing her of being unfaithful, calling her a "treacherous slut" and talking of ending it all.

Despite the text, the pair caught the bus to visit her grandmother's grave when they began arguing, and got off the bus.

Then, Sporton began to attack her. The woman fell as she tried to get away and, the court was told, several motorists stopped.

The woman told passersby Sporton had a knife and was trying to kill her. Witnesses saw him drop a large knife, pick it up again and put it back into his clothes.

Mr Bertocci also stopped his car and got out. After a scuffle, Sporton pulled out the knife, chased him and stabbed him three times to the chest and abdomen. He died at the scene.

Sporton then barricaded himself inside an Altona North home with his girlfriend, before being arrested after a nine-hour siege.

Justice Beale said Sporton had murdered a popular father of two, whose youngest daughter - now only two years old - would grow up never knowing her father.

"His death was a tragedy and the repercussions from that death are far-reaching."

Justice Beale praised Mr Bertocci who, in stopping to help a woman in need, "showed compassion and courage".

Justice Beale said that if it weren't for Sporton's guilty plea, he would have sentenced him to 23 years' jail.

He accepted that Sporton was remorseful for his actions, and had told a doctor: "I feel terrible. If I could turn back time I would, 100 per cent".

Outside court, Mrs Bertocci said Sporton's extensive criminal history showed that "therapeutic case management" was not working to protect the community.

"Really, we've got to get back to the basic and strong case management of offenders, especially the young offenders," she said.

"We all hold Roger very high up on a pedestal and he [committed] an act of bravery and [was] a true gentleman and a great person indeed."