A Brisbane man's schizophrenia played no role in his decision to beat a Korean woman to death and dump her body in a park, a Queensland court has heard.

Alex Reuben McEwan has confessed to killing Eunji Ban near the city centre in November 2013, but pleaded not guilty to murder on the grounds his mental illness left him unable to control himself.

McEwan has told the jury in his Brisbane Supreme Court murder trial he was possessed by a demon when he attacked Ms Ban and dragged her body to nearby Wickham Park where he left it under a tree.

Alex McEwan is accused of murdering Korean student Eunji Ban. (9news)

He was later diagnosed with schizophrenia, but defence barrister John Allen QC has argued his client was suffering the illness when he killed the 22-year-old.

However, treating psychiatrist Angela Voita has testified McEwan's schizophrenia did not influence his behaviour during the attack.

Dr Voita is clinical director of The Park Centre for Mental Health and believes McEwan's violence was rather fuelled by alcohol and that his schizophrenia was brought on by the stress of being in custody.

"Because it was violent, it doesn't mean it was due to a mental illness," she told the court on Friday.

"There doesn't appear (to be) any significant change in his behaviour or how he interacted with others to suggest he was experiencing a psychotic episode."

Psychiatrist Angela Voita is seen outside the Supreme Court in Brisbane. (AAP)

McEwan had been drinking with friends at his Spring Hill unit in the hours before he roamed the streets and spotted Ms Ban walking to work.

Dr Voita said the accused told of seeing visions of a demon for the first time after his arrest, contrary to his testimony it had been present since he was a child.

McEwan told Dr Voita he had exaggerated his symptoms and wanted his family to believe he killed Ms Ban because of his mental illness rather than "evil".

A sketch of McEwan in court. (AAP)

McEwan, who regularly used marijuana, also said he'd experienced violent fantasies throughout his life and had killed animals.

"I thought there was a sense of entitlement at times, part of a narcissistic flavour where he was quite assertive at times, thought he was special in some way," Dr Voita testified.

Another psychiatrist, Donald Archibald Grant, said he believed McEwan was "troubled" but not psychotic in the lead up to killing Ms Ban.

He said McEwan appeared in control of what he was doing but may have been in a disassociative state.

"During the action, he had attempted to conceal what he was doing," Dr Grant said.

"That indicates to me a very willed and controlled action."

The trial will resume on Monday.