A man has told a South Australian court that it felt like "getting hit by a car" when his dying friend confessed to a 2009 murder that someone else was serving time for.

Daniel Troy Ames, 49, was convicted of murdering his 68-year-old uncle Allan Ames at his Cavan workshop in November 2009, and received a minimum 24-year sentence.

He has already served more than a decade behind bars in Murray Bridge and has today launched a fresh bid for freedom in the Court of Criminal Appeal.

The murder weapon has never been found and the Supreme Court found Ames had no clear motive to kill his uncle.

At trial, Justice David Peek relied on evidence that Ames lied about how long he had visited his uncle on the night of the murder and CCTV that showed sensor lights did not illuminate at any other time.

But his lawyers now claim convicted drug trafficker Peter Lagerwey confessed to the murder in front of his wife and friend Craig Peterson at the Queen Elizabeth Hospital in July 2016.

This morning, Ames told Justices Mark Livesey, Sophie David and Chris Bleby that his uncle asked him to come to his workshop that night to discuss a family matter before leaving just after midnight.

"He was very flustered that night, looking for something. I offered a few times to help, and he said no," he said.

He said it did not feel like he was at his uncle's workshop for two hours.

Prosecutor Jim Pearce asked Ames why he showered before he left to see his uncle and again afterwards.

Ames responded: "That place was a s***hole … I'd been at a filthy workshop, and I wasn't going to get into bed".

Ames said he was out for breakfast at Caffe Buongiorno the next morning when he got a call his uncle had been killed.

"When I got that phone call, our world turned upside down," he told the court.

Ames told the court he had met Mr Lagerwey — who he had been with earlier that day — through the gym. 

Mr Lagerway introduced him to Craig Peterson.

Giving evidence, Mr Peterson said Mr Lagerwey told him he had murdered "Danny's uncle" in the days before he died of cancer.

He told the court he decided to meet with Ames's lawyer at the time, Stacey Carter, and tell her about the confession in early 2017.

Mr Pearce asked Mr Peterson what his reaction was when his friend confessed to murdering Mr Ames and why it took him five months to come forward.

"Yes, it was like getting hit by a car. I was in shock and didn't know what to do," Mr Peterson responded.

He told the court it took him a while to tell anyone about the confession because he wanted Peter Lagerwey's wife to come with him, but despite initially agreeing, she became reluctant.

Mr Pearce asked the witness whether he was fabricating the confession, and Mr Peterson responded: "No".

Ames is not seeking an acquittal, but wants a retrial.

Outside court, Doug Ames said his son should never have been convicted and this appeal was his last hope at freedom.

He said if the appeal fails, Ames will have to serve his minimum 24-year jail term.