A witness and long-time friend of the accused killer told the Supreme Court on Friday that he had been with a group, who were working on a car, five days before the alleged murder and that there hadn't been any trouble, to begin with.

But the witness, Jarrod Peter Wallis, of Ballarat, told the jury Darren Wilson, 34, began to show signs of frustration towards his cousin, Peter Williams, and that he later heard Wilson discussing a plan to lure his cousin to a house and bash him.

EARLIER IN THE TRIAL:

The witness told the jury that he, Wilson and another man were due to go back Mr Williams' home for a third day to work on the car, but that Mr Williams had contacted police and said they were no longer welcome.

The jury on Thursday heard that Wilson, after a day helping his cousin, later allegedly broke into Mr Williams' home, rearranged furniture and left a threatening note.

Wilson has pleaded not guilty to the gruesome murder in which Mr Williams' stepson, Timothy O'Brien, died from "severe trauma" to the head after allegedly being struck at least 20 times with an axe.

Timothy's body was discovered by police at a Scarsdale home on January 5 last year.

Crown prosecutor Andrew Tinney SC told the jury Wilson had been warned by police not to go near Mr Williams or his family after the incident in which he allegedly broke into their home.

The jury heard Wilson told a local officer he would kill Mr Williams, but that the police member took it as a "throwaway" line.

The jury heard Wilson and another man were picked up by an associate, Lisa Trezise, the night before the alleged murder.

Trezise, with her two young children in the car, drove the men to the Scarsdale house before she and two teenage girls drove to Mr Williams' home and lured him back, telling him they were scared of prowlers.

Mr Tinney told the jury Timothy, armed with a baseball bat, went with his stepfather because of an "inseparable" bond between the pair.

Timothy used the baseball bat to first hit Wilson after he jumped from a room and began bashing Mr Williams.

Timothy also hit the another man before being chased him out of the home. The man jumped on his back and allegedly began hitting Timothy with the blunt side of the axe.

The jury heard Wilson then came out of the house, picked up the axe, turned it to its bladed side and allegedly struck Timothy several times before warning Trezise that she and her kids would be next if she didn't shut up.

The trial before Justice Betty King continues.