Socialite Maureen Boyce's lover told police she went "berserk" the night before her death because she thought he was having an affair with his elderly aunt, a court has heard.
New Zealand-based doctor Thomas Chris Lang is on trial in the Brisbane Supreme Court after pleading not guilty to murdering the 68-year-old at her Kangaroo Point sub penthouse in 2015.
The court has heard Lang called emergency services on the morning of October 22 after finding Ms Boyce dead in her bed with a knife her abdomen.
Crown prosecutor David Meredith has told the jury they must decide whether Ms Boyce took her own life or if she was killed by Lang in a "jealous rage".
In a police interview played to the court today, Lang told an officer Ms Boyce was upset the night before by a text he received from his aunt.
"She thought I was having an affair with my 80-year-old aunt," Lang said.
"No matter how much I explained to her, it didn't matter."
Lang said Ms Boyce threw her phone off the balcony some time before 9.30pm then went to bed, ordering him to sleep elsewhere in the apartment.
In the emergency call, Lang told the operator he believed Ms Boyce's knife wound was "self-induced".
The court heard he also told police the former model had suicidal issues in the past, took prescription drugs and alcohol the night she died and previously commented on the sharpness of her cooking knives.
A forensic officer testified yesterday that Ms Boyce was found with the fingers of her left hand touching the handle of the knife, which penetrated her back.
Her children have told the court their mother was right-handed and suffered from arthritis in her fingers.
The trial continues.