Prosecutors in the trial of a Qld mechanic accused of murder have told a court the man was under financial strain when he allegedly killed a couple in 2012.

A mechanic accused of murdering a couple in far north Queensland is a big-noter and has told lies, but is no killer, his lawyer has told jurors.

Brandon MacGowan, 43, is on trial in the Supreme Court in Cairns for the alleged murders of Mount Isa couple Scott Maitland and Cindy Masonwells whose bodies were found in scrub near Cairns in 2012.

Prosecutors allege the couple were killed over a long-standing dispute over $14,000 worth of restoration work on their panel van that MacGowan had allegedly been paid to do but failed to carry out.

It’s alleged he killed the Mount Isa couple after collecting them from the Cairns airport on the evening of July 5, 2012.

MacGowan has told jurors during the trial that he didn’t kill the pair.

At the centre of the prosecution case is a white van which was allegedly found in a Cairns car park stained with Ms Masonwells’ and Mr Maitland’s blood.

MacGowan has said he last saw the couple on the evening of July 5, 2012, when they left his workshop in a white van he gave them to use.

On Wednesday, his defence lawyer Josh Trevino argued during his closing address that there was insufficient evidence to convict his client.

“That he would kill two people over a panel van quite simply doesn’t make sense,” he told the court.

He pointed to there being no blood on clothes or boots found in MacGowan’s room and that his DNA was not detected in the white van.

Mr Trevino said evidence given by a number of crown witnesses couldn’t be relied on and that just because MacGowan had initially lied to police about some of the evening’s events didn’t make him guilty.

Those lies included that the couple drove off in their panel van and that he hadn’t driven himself to a friend’s house that evening.

“He’s a big-noter, he’s a blowhard, but that doesn’t make him a murderer,” Mr Trevino said.

“[At the time] he had no idea that what he’d told police would end up assuming such importance.”

Crown prosecutor Todd Fuller said during his closing address that MacGowan had spent the $14,000 the couple had paid him and he was stressed because he hadn’t carried out the work on their van.

“His only response to that was violence, extreme violence,” he said.

“He took advantage of his relationship with these people when they were in a vulnerable position and he killed them.”

He said a witness testified the bloodied van found after the couple disappeared was the same one MacGowan drove to a friend’s house in the early hours of July 6, 2012. The same witness said the accused was injured and had blood on his clothes.

It’s alleged Mr Maitland died from a single gunshot wound to the head and Ms Masonwells was stabbed to death.

Justice Jim Henry is expected to finish summing up evidence on Thursday.