McEwan sorry he killed 'girl', trial hears

The man accused of the bashing murder of a Korean woman in a Brisbane city park told a friend he killed someone because he "wanted a way out" and was "sorry that it was a girl", a court has heard.

Alex Reuben McEwan has pleaded not guilty to murdering 22-year-old Eunji Ban at Wickham Park in the early hours of November 24, 2013.

The Brisbane Supreme Court has heard Ms Ban was walking to a shift as a hotel cleaner when she was bashed to death by McEwan.

McEwan's former housemate Blake Cooper testified on Thursday he was "speechless" when McEwan told him he'd killed someone in a phone conversation later that morning.

He said when he asked his friend why he did it, McEwan replied he "wanted a way out".

"(He said) he was sick of everything and he just did it to the first person he saw and he was sorry that it was a girl," Mr Cooper said.

McEwan's sister Emma also told the court her brother was "acting strange" that morning and told her "something bad had happened".

Ms McEwan said she had been very close to her brother during their childhood but he had become withdrawn and angry in recent years.

The court heard Ms McEwan told a friend on Facebook the night her brother was arrested that he had "serious mental health issues".

"He was not sober when it happened and he says he was possessed," the Facebook message said.

"I believe him, and he has been showing signs of this ever since he was 16."

In a teary testimony, Ms McEwan said she just tried to make people know it wasn't really her brother.

"I didn't want people to think he was a horrible person because he's not," she said.

The court has heard it is not in contention that McEwan killed Ms Ban, but the trial is necessary to determine his mental state at the time and whether or not relevant legal defences, such as insanity, apply.

The trial will continue before Justice Jean Dalton on Friday.