Ms Silva has pleaded not guilty to the stabbing murder of Mr Polkinghorne, 28, outside her family's Marrickville home on Mother's Day, 2012.

The 24-year-old says she was acting in self-defence having suffered ongoing physical and emotional abuse in the months leading up to the incident, and had been threatened repeatedly on the day in question.

The court has heard that Mr Polkinghorne arrived at Ms Silva's parents' house in an ice-fuelled rage, threatening to "cave her head in" shortly after 9pm.

He got into a fight with Ms Silva's brother Miguel, and Ms Silva allegedly went into the house and returned with a knife before stabbing him up to five times.

The court heard on Thursday that, when police searched Ms Silva's bedroom after the incident, they found an undated note from Mr Polkinhorne scrawled on a piece of cardboard.

"Jess I'm sorry yesterday was as angry as it was," said the letter, which was read to the court.

"I'm sorry that I put my hands on you … when it has never happened before.

"We both obviously love each other but we could be better off going our separate ways … Jess, I'm sorry and I love you."

Later, Mr Polkinhorne's stepsister Jasmin Williams told the court about an apparent domestic violence incident when Mr Polkinhorne and Ms Silva came to Brisbane in 2012,

Ms Williams said she had heard a series of bumps late one night.

The next morning, Ms Silva said her partner had "gone psycho" and hit her the night before, and then choked her with his hands.

"She told me what happened and she was angry and she said: 'If he does it to me again I'm going to kill him,' " Ms Williams said.

The trial continues.