Garrard was caught in a headlock when he stabbed the 24-year-old tradie in the stomach at Doveton on July 19, 2018.

The intellectually impaired killer will spend up to seven years behind bars for Mr Husseini's manslaughter.

Garrard was jailed in the Supreme Court of Victoria on Thursday for a minimum of five years.

"There is nothing that I can say or do to bring back Mr Husseini to heal the grief and pain his family feels," Justice Rita Incerti said.

"They have lost a loving son and brother. They speak as one with feelings of grief, depression, paranoia, anxiety, anger, loss of trust in others, and loss of enjoyment in work and social life."

Garrard had agreed to sell Mr Husseini drugs at the milk bar before the pair fought outside.

The victim had Garrard in a headlock when the latter pulled a 30cm knife from his jacket.

He stabbed Mr Husseini once and fled, leaving the man to die.

Justice Incerti accepted Garrard had been in a vulnerable and threatening situation but said his response was excessive.

The killer had started using cannabis when he was about 11, before moving on to heroin and methamphetamine.

Garrard had a traumatic upbringing and only learned to read to a grade four level.

He is doing courses including a drug and alcohol program behind bars.

"I accept that you have a genuine desire to change,"Justice Incerti told the man.

"I believe you when you say you want to work and be a normal person in society, away from crime and that you do not want a part of drugs."

Garrard has already spent almost 18 months in jail awaiting sentence.

Australian Associated Press