An accused murderer embroiled in a complicated love triangle cannot be convicted because of a lack of evidence, a defence barrister says.

Gofal Baziad, 54, has pleaded not guilty to the 2004 murder of Jason Palmer, the ex-husband of his on-again-off-again partner Remmy.

Baziad left Australia for five years about a month after Palmer's body was found in the Nepean River with substantial torso wounds.

READ MORE: Queensland MP Jimmy Sullivan found dead

But Baziad's barrister told a NSW Supreme Court jury today the prosecution's circumstantial case did not have enough evidence to find the love rival responsible for Palmer's death.

"There will be a lot of witnesses and a lot of detail," Madeleine Avenell SC told the jury in her opening address.

"[But] you won't be able to be positively satisfied of the ultimate question: has the prosecution proved beyond a reasonable doubt that Baziad was the person responsible?"

Jason and Remmy Palmer had been married and had a "somewhat intertwined" life with Baziad, Avenell said.

But the exact nature of Baziad's relationship with Palmer before her ex-husband's death would be subject to evidence in the trial, the defence barrister said.

Baziad left Australia on March 28, 2004 and did not return until 2009, the jury heard.

Why he left the country and did not return for so long is expected to be a matter of dispute in the trial, Avenell said.

READ MORE: Trump rages at some of his biggest former backers in lengthy Truth Social post

Palmer also left the country and was in a subsequent relationship with Baziad for many years, the jury was told.

Crown prosecutor Brett Hatfield SC said Baziad was a jealous man who tended to act violently when he saw Palmer with another male.

Evidence is expected to be given that Baziad attacked a man in a hardware store carpark, with whom Palmer was having a relationship after leaving Baziad in 2018.

Palmer is expected to testify at trial that she always had strong feelings for her ex-husband and wanted to make him jealous through her relationship with Baziad.

In December 2003, the trio met to discuss the situation, and Palmer was asked to choose between the men.

When she chose her former husband, Baziad indicated he accepted the decision, Hatfield said.

However, Palmer was seen for the last time months later, walking out of his partner's home in Sydney's south west with his friend Baziad on February 6, 2004.

The trial continues.

LIVE UPDATES: New warning for Iran; Israel condemned for Lebanon attacks

NEVER MISS A STORY: Get your breaking news and exclusive stories first by following us across all platforms.

• Download the 9NEWS App here via Apple and Google Play
• Make 9News your preferred source on Google by ticking this box here
• Sign up to our breaking newsletter here