The caution came after Ms Conlon showed him bruising on her arm that he suspected had been inflicted by boyfriend Aleksander Vojneski.

But the mother-of-three denied Mr Vojneski had caused the injury.

Mr Vojneski, 31, is on trial in the ACT Supreme Court for her murder. He has pleaded not guilty.

Ms Conlon, 30, was found dead in the bedroom of her Macgregor home with 11 stab wounds on March 28, 2012.

The Crown alleges Mr Vojneski murdered her at the northside home on the night of March 27 after he became frustrated by his failure to get drugs.

Scott Conlon told the ACT Supreme Court on Tuesday that she had shown him bruises on her arm only a month before her death. She said she received the injuries after being mugged in her driveway as she stepped out of her car.

Mr Conlon said he asked her if Mr Vojneski had been responsible, but she looked him in the eye and denied it. He then warned her not to be around people who would hurt her.

Mr Conlon’s reports of bruising collaborated evidence presented to jurors earlier in the trial.

In the hearing's first week, the court heard Ms Conlon and the accused’s relationship – which developed after the pair met in a psychiatric ward in October 2011 – had been volatile and blighted by frequent splits and reunions.

A friend of Ms Conlon’s gave evidence about an incident in which Mr Vojneski had locked his girlfriend out of his Hawker unit. The woman said Ms Conlon had described how Mr Vojneski had allegedly held her over a balcony and threatened to drop her.

The witness told the court Ms Conlon had bruises on her arms and under her arm that were consistent with the alleged balcony incident.

Earlier in the day, a friend of the defendant’s brother contradicted evidence he told the court on Monday about the morning after Ms Conlon’s murder.

The man – who was employed in Mr Vojneski’s brother's cleaning business – found Mr Vojneski asleep in a work van in his driveway at about 7.30am on March 28.

The witness originally told jurors he had invited the accused inside and provided him with a change of shirt. On Monday, he identified a photograph of a shirt he had provided to Mr Vojneski.

But on Tuesday the man admitted he could not be certain the shirt was his and could not remember giving the shirt to Mr Vojneski.

Under cross-examination by defence barrister Jack Pappas, he denied ''colouring up'' his evidence in order to divert police attention.

The trial before Justice John Burns continues on Wednesday.