Muesli company boss Peter Pavlis apologises for murdering co-director

An elderly Melbourne muesli company boss who brutally murdered his business partner has described her as a "nice person" during an in-court apology that the victim's family found hard to take.

Peter Pavlis, the 76-year-old founder of The Muesli Company, has pleaded guilty to murdering his co-director Jennifer Borchardt, 49, at her Richmond home on July 25, 2017.

In a pre-sentence hearing in the Supreme Court today, prosecutors said Pavlis killed Ms Borchardt out of "jealousy or anger" that morning before heading to work as if nothing was wrong.

Colleagues told the court about the heartbreak of losing Ms Borchardt.

“She trusted you and always wanted to protect you from any hurt or harm. Ironic, isn't it?" Rosa Cornelia said.

"I still can't understand for the life of me how you could've come to work that Tuesday as if nothing had happened."

Ms Borchardt's aunt Carlie Smith described Pavlis's actions as those of someone who was "pure evil".

"It disgusts me. You left her lying there, helpless, afraid and dying," she said.

After Ms Borchardt's supporters gave their emotional statements, Pavlis asked the judge if he could speak too.

"I'm sorry," he said slowly as he stood in the dock in a suit.

"What I did I had no right to do. I still can't understand how I did it.

"She was a nice person and I couldn't have done anything without her.

At the time of the killing Ms Borchardt was living with her boyfriend Robert Hansen, who she'd met about six months earlier.

Mr Hansen returned home to find Ms Borchardt's lifeless body on the floor, a haunting image now etched in his memory.

Defence lawyer Peter Morrissey SC said Pavlis was known as a gentle man and the frenzied stabbing was out of character.

"It looks like something flared up, and it looks like there was a crazy overreaction by him," he said.

In terms of what sparked the killing, prosecutor Mark Rochford SC said Pavlis may have become jealous of Ms Borchardt's relationship with her boyfriend.

Ms Borchardt died from multiple stab wounds to her neck and chest and had defensive wounds on her hands, an autopsy found.

Pavlis tried to clean up the scene and avoid detection immediately after the killing but pleaded guilty at an early stage.

He will be sentenced by Justice Lesley Taylor at a later date.

The Muesli Company, started by Pavlis in 1984, operates from Thomastown and produces wholegrain breakfast cereals.

With AAP