Marc Robertson has been sentenced to five years and six months in prison for the manslaughter of his former partner’s new boyfriend in a spontaneous knife attack in Victoria.
The 43-year-old pleaded guilty to killing Aaron Grant, who was dating the mother of Robertson’s four children. With time already served, he will be eligible for parole in June 2028.
Victorian Supreme Court Justice Amanda Fox said Robertson did not intend to kill Mr Grant and had not planned to use the large knife he took to a home in Seymour.
Robertson went to the property in the early hours of March 29, 2025, amid animosity involving Mr Grant and another man, Steve Barns. Robertson believed Mr Barns had impregnated his new girlfriend.
The three men were inside Mr Barns’s home when Robertson began ranting that the two men had taken everything from him and that he had nothing.
He then insulted the mother of his children, referring to her as either a “junkie” or a “whore”. Mr Grant responded by launching himself at Robertson, and the pair began grappling while Robertson was still holding the knife.
The weapon entered Mr Grant’s chest. CCTV showed him crying out for help as Robertson fled through the front door, saying: “I f***ing warned you.”
Paramedics attempted to revive Mr Grant, but he died on the way to hospital at about 4.20am. Robertson was arrested later that day.
Justice Fox said Robertson had been in the grip of a methamphetamine addiction at the time and had felt aggrieved by Mr Grant.
But she said carrying a knife was inherently dangerous and had transformed what could otherwise have been a fight into a far more serious offence.
“As the events of this night show, by carrying a knife you turned what might otherwise have been a fight … into a very serious crime,” Justice Fox said.
Robertson looked relieved as the sentence was handed down on Wednesday morning. The judge noted that he had since shown remorse, including through his guilty plea and a letter to Mr Grant’s family in which he accepted responsibility for his actions.
