Coskun Jaques Marius, 30, Â this month pleaded guilty in Brisbane Supreme Court to the manslaughter of Tane Tahi Manawa, 38, at the victim's Surfers Paradise home on May 10, 2019.
Marius pleaded not guilty to the murder of Mr Manawa on the grounds of having an abnormality of the mind at the time and the matter was taken to trial.
The prosecution concluded its case on Tuesday, following six days of hearings, and Marius decided to testify in his own defence.
Marius's barrister Lars Falcongreen told the jury his client had suffered a tormented childhood and developed an alternative personality called 'Si3ge' as a "dark angry force" to help him cope.
The jury had earlier heard audio from a police interview with Marius in which he said Si3ge could take over his thinking whenever he became enraged.
Marius took the stand and said he used Si3ge in response to being bullied at school.
"He was sort of like my protector. He gave me mental confidence," Marius said.
Marius said he had been homeless, unemployed and using methamphetamine in the months prior to the killing, but Mr Manawa had offered him accommodation in return for performing housework
The jury heard claims Mr Manawa, known to his friends as Dre, had later turned abusive and violent towards Maruis.
"He pushed me around the yard, telling me I would sleep in the shed like a dog," Marius said.
Marius said he formed the belief that Dre had been drugging and sexually assaulting women including a close family member.
Before the killing, Marius said he had "uncontrolled thoughts" and could hear an angry and vengeful Si3ge whispering in his ear to stand up for himself.
"I just blacked out, then I could feel me swinging and hitting him with the lat pulldown bar," Marius said.
Dre suffered extensive head injuries from being repeatedly hit with the metal bar and took an estimated 45 minutes to die after being attacked while sleeping in a reclining armchair.
Under cross examination by Crown prosecutor Michael Lehane, Marius denied telling the dying Dre that "I'm the one that got you".
"I said 'I'm sorry, I love you, but I hope you suffer,'" Marius said.
Mr Lehane questioned why an imaginary protector who "said sorry for nothing" would make such an apology and Marius insisted the Si3ge personality was still in control at that point.
Marius also admitted to telling several lies to other people in the house with the effect of leaving Dre by himself and agreed that his actions after the killing, including stealing Dre's van and selling his possessions for drug money, were "deliberative".
Marius is due to continue giving evidence on Wednesday, followed by two psychiatrists who have been called to testify about his state of mind at the time of the killing and subsequent mental health treatment.
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