A man has described how his accomplice used a pick handle to bash a tied-up man five or six times in the head with "extreme force" that killed him during a home invasion.
After they fled the house later, the friend allegedly said he was pretty sure pig farmer Keith Cini "died when I caved his f***ing skull in", a jury heard.
The man, who can't be named for legal reasons, told the NSW Supreme Court that as he and Ryan David Evans crept towards Mr Cini's Badgerys Creek home in the early hours of May 30, 2014, a light was on inside and dogs started barking.
"It was a very dark night obviously, I couldn't see where they were," the man said on Tuesday.
"At this point I said 'f*** this, let's go'."
But Evans smashed a window of the house with a pick handle and disappeared inside, the man said.
"About 15 seconds later - 10 to 15 seconds later - I heard a woman screaming."
The man gave evidence on Tuesday at the trial of Evans, 28, who has pleaded not guilty to seven charges related to two violent home invasions.
He is accused of attacking Brett Delamont during a break-in at his Southern Highlands home in April 2014, and of murdering Mr Cini and attempting to murder his partner Lucina Boldi in another home invasion a month later.
Evans' former friend, who has been convicted over his role in both the break-ins, said they were told they could find more than $10,000 cash in Mr Cini's study.
He said that after hearing the woman's scream, he followed Evans through the window, and found Mr Cini unconscious with blood on his head.
He couldn't get into the room where he assumed Evans was beating a screaming Ms Boldi, but soon she was quiet, too, he said.
After they tried unsuccessfully to open the study door, they returned to find Mr Cini sitting up as he tried to remove the duct tape binding his feet, the man said.
Evans allegedly struck him another five or six times with "extreme force".
"It was at this point that I said 'This is f***ed mate'," he said.
"I left back out through the lounge room ... and got back into the car."
He also told the court how he and Evans broke into Mr Delamont's Medway home a month earlier, leaving with a sum of cash.
He denied under cross-examination by defence lawyer Robert Webb that he had struggled with Mr Cini, and that he was the one who struck Mr Cini and Ms Boldi.
The trial continues.