The sister of a man accused of murdering a young Korean woman in Brisbane's CBD has broken down in tears while giving evidence at his trial.
Emma McEwan testified that her brother Alex McEwan was "acting strange" hours after he killed Eunji Ban.
The 23-year-old has formally admitted to causing the 22-year-old student's death in Wickham Park in November 2013 but denies it was murder.
His barrister is expected to run a defence of insanity.
Ms McEwan told the court the morning of the killing, her brother was not talking to her as much as usual and he was making her feel nervous.
"I remember saying 'what the f*** is wrong with you?'" Ms McEwan said.
"He said something was really wrong with him.
"When I asked him how bad it was, he said it was really bad."
Under cross-examination by defence barrister John Allen, Ms McEwan said she started noticing differences with her brother when he was 16.
"He became more withdrawn," she said.
"His temper was a lot shorter.
"Sometimes I heard a lot of banging on the wall, sometimes talking or yelling in his sleep."
Mr Allen read out a Facebook message Ms McEwan sent to a friend after her brother's arrest where she said she believed her brother when he said he was possessed.
"I think I was just trying to make people know that it wasn't really him," Ms McEwan told the court.
"I just didn't want people to think he's a horrible person, because he's not."
The trial continues.
