Vic man's good deed cost him his life

A Melbourne man with the "decency and courage" to go to the aid of a pregnant woman trying to escape her aggressive lover paid for his bravery with his life.

Roger Bertocci, 46, was stabbed to death on December 14, 2014 after he stopped his car at the scene of a fight between Jonathon Sporton, 22, and his girlfriend Kesaia Leveni.

Ms Leveni had fallen over after being chased by Sporton on a busy street in Altona North in broad daylight, where Sporton was heard saying he had a knife and was trying to kill her.

Mr Bertocci was one of several motorists to stop.

Sporton approached Mr Bertocci's car and tried to punch it, but was pulled away by Ms Leveni.

After an unarmed Mr Bertocci got out of his car, Sporton became aggressive, pulled out a chef's knife and chased Mr Bertocci before stabbing him to death.

It was a horrifying and unjustified attack, Victorian Supreme Court Justice Christopher Beale said in jailing Sporton for 21 years on Friday.

"You murdered Mr Bertocci because you took exception to him intervening in your dispute with Ms Leveni," Justice Beale said.

"You were the aggressor even before Mr Bertocci got out of his car."

Sporton is a paranoid drug user with a long history of violent offending, Justice Beale said.

He was on a suspended sentence when he murdered Mr Bertocci.

He believed the baby Ms Leveni was pregnant with at the time of the murder was his best friend's child, even though she had pointed out to Sporton that the best friend was in prison when the baby was conceived.

In a victim impact statement, Mr Bertocci's sister Stefanie Gregor said she wished her brother hadn't stopped his car, but he always put the welfare of others before himself.

"I'm very proud of my brother, he did an act of bravery," she said.

Sporton must serve a minimum of 17 years before being eligible for parole.