A man found the body of his 36-year-old son in a pool of blood and positioned almost like he was trying to crawl away from something, a court has heard.
James Switez-Glowacz died from haemorrhaging, having been stabbed eight times in his head and body days before his body was found in February 2018.
His former wife Emily Jane Tracey, 38, and another man she also had a relationship with - 37-year-old Paul Mathew Moore - are standing trial each charged with one count of murder.
Tracey and Mr Switez-Glowacz had married, divorced and talked about getting back together during an "on-again-off-again relationship" after meeting when she was 16 years old, the Brisbane Supreme Court has been told.
They had a daughter, and Tracey, of Russell Island, also has twins with her co-accused.
Albert Switez-Glowacz went to his son's unit in the Brisbane suburb of Wynnum West on February 8, 2018 as he had been unable to reach him by phone for days, the court heard on Wednesday.
There was no answer when he knocked and Albert Switez-Glowacz found the screen and wooden doors unlocked.
That was unusual because James Switez-Glowacz was "pretty fastidious" about security, his father said in a recorded interview played to the court.
"He didn't have a lot of possessions, but what he had he wanted to keep," Albert Switez-Glowacz added.
He said he saw dry blood on the floor, just inside the door, and blood splashes on the wall.
He found his son "tucked in the corner" of the lounge-room.
"He was positioned almost like he was trying to crawl away from something," he told the court.
James Switez-Glowacz was on his hands and knees, with his face touching the floor or close to it.
"He had his right arm up behind his back and there was just blood everywhere," Albert Switez-Glowacz said.
His blood-soaked T-shirt was pulled up from the back over his head.
James Switez-Glowacz had mental health issues, was on medication and had an alcohol and drug problem.
He also spent time in jail for assault.
"It's clear that James Switez-Glowacz wasn't an angel (and) it's accepted that there was some violence in his relationships which his family says was in the context of his drug abuse," prosecutor Danny Boyle said earlier.
But in the weeks leading up to his death James Switez-Glowacz was "looking the best that he'd ever looked", his father said.
He was enjoying being a father to his and Tracey's daughter.
"He had a much happier disposition," Albert Switez-Glowacz added.
James Switez-Glowacz's mother Debbie Goodlet also told the court her son was "at the best" she had ever seen him in the weeks before his death, having moved into the home he wanted for him and his daughter.
"He looked great, he was making good decisions," she said tearfully.
"It's the James we always wanted and we only had him for a little while."
Barrister John Fraser said in his opening statement Moore admits he stabbed Mr Switez-Glowacz, but the issue for the jury will be whether his actions were unlawful.
Tracey's barrister Leon Ackermann told the jury the prosecution had put up three scenarios about the killing including claiming Tracey drove with Moore to Mr Switez-Glowacz's house
"I expect an issue in this trial will be whether there was ever any common intention with Mr Moore to seriously assault the deceased," he said.
The trial continues before Justice Martin Burns.