A man has pleaded guilty to manslaughter after fatally stabbing his former partner's new boyfriend during a confrontation at a house in regional Victoria. Marc Robertson, 43, had gone to the Seymour home armed with a knife and was ranting about losing everything when Aaron Grant, 28, confronted him and the pair grappled, resulting in the fatal stab wound. The case highlights the volatile dynamics that can follow a relationship breakdown, with the court told Robertson had been abusing methamphetamine and was emotionally troubled at the time.

The stabbing occurred in the early hours of 29 March 2025 at the Seymour home of a mutual friend, Steve Barns, about 100km north of Melbourne. CCTV captured Grant crying for help as Robertson fled, saying "I f***ing warned you"; paramedics could not revive Grant, who died en route to hospital around 4.20am. Robertson, who was originally charged with murder, told police he had acted in self-defence, and his defence barrister said he had not intended to kill Grant, was remorseful and had reasonable prospects of rehabilitation. He will be sentenced by Justice Amanda Fox at a later date.