A "DEMON" was blamed after Alex Reuben McEwan brutally attacked a young woman, his murder trial was told.
Korean student Eunji Ban died after suffering "extensive, disruptive facial injuries" from repeated blows to her forehead, prosecutor David Meredith said on Monday.
She was set upon in Brisbane on Sunday November 24, 2013 simply because Mr McEwan had "gone out looking to kill someone", Mr Meredith told Brisbane Supreme Court.
Mr McEwan, 23, mentioned a lifelong "demon" plaguing him, defence counsel John Allen said.
The murder trial is not about who killed the Korean student - but whether Mr McEwan was of sound mind when Ms Ban was attacked near Wickham Park on her way to work at the Transcontinental Hotel.
Luke Appleton said former Ipswich man Mr McEwan was his best friend.
Mr Appleton told jurors his mate called him on the day of the killing with an unbelievable story.
"He just came straight out and said: I killed someone."
Mr Appleton asked if his friend had been driving and hit somebody.
"He said: No, I just punched someone in the face, kept kicking her, punching her, then dragged her body."
"I was pretty gobsmacked," Mr Appleton added.
He thought his friend was joking - but then saw a news report about a body found in Brisbane CBD.
"I spoke to my dad first because I didn't know what to do. I was in a dream for two days - it didn't hit me till Monday afternoon."
Mr Appleton said his mate had not smoked marijuana for a while, and was a placid, peaceful man.
Mr Meredith said Mr McEwan made multiple admissions to friends about attacking Ms Ban, who was 22.
The injuries meant Ms Ban had a "rapid loss of consciousness".
The prosecutor said a Queensland Health scientist found links between Ms Ban's blood and Mr McEwan's DNA at the crime scene near Roma Street Parkland.
Mr Meredith said the jury would hear Mr McEwan stomped on the South Korean student, who was breathing in her own blood and had little chance of surviving the assault.
Mr McEwan spoke after the killing of "a demon that had been troubling him his whole life", Mr Allen said.
"It didn't feel like it was him who did it. It felt like he was possessed."
Mr McEwan also told his mum about a "a sphere or ball rolling around his head", Mr Allen said.
The defence lawyer said his client referred to watching the attack on Ms Ban, and it seemed like "someone else was doing it."
On Monday morning, Mr McEwan pleaded not guilty to murder.