Family and friends of a couple murdered by a Queensland mechanic applauded when the judge sentenced the killer to a minimum of 30 years behind bars.

A Queensland mechanic will spend at least 30 years behind bars for the execution-style killing of two customers over a financial dispute involving a panel van.

Jurors took about two hours to find Brandon MacGowan, 43, guilty of murdering Mount Isa couple Scott Maitland and Cindy Masonwells in Cairns in July 2012.

Friends and family of the couple applauded when he was handed two life sentences in the Supreme Court in Cairns on Friday.

“Your calculated, callous execution of Mr Maitland and Ms Masonwells, essentially to eliminate the financial problem they presented to you, involves such a high level of culpability,” Justice Jim Henry said during sentencing.

The court heard MacGowan killed the couple, who were in their 30s, because of a long-standing dispute over $14,000 worth of restoration work he had agreed to do on Ms Masonwells’ 1970s panel van.

He collected the couple from the Cairns airport on July 5, 2012, before shooting Mr Maitland in the back of the head and fatally stabbing Ms Masonwells in the back.

Their bodies were dumped in scrub near Cairns.

MacGowan denied the murders, telling the court the last time he saw the couple was when they left his Cairns workshop in a white van on the night they were killed.

Justice Henry said MacGowan was under mounting pressure because he had spent the couple’s money while telling them he had carried out the work on their van even though he had not.

He said MacGowan had been caught out by his lies and the “plethora” of circumstantial evidence against him.

Crown witnesses included two men who recalled seeing a screaming woman fall out of a parked van MacGowan was driving on the night of July 5, 2012.

CCTV showed MacGowan collecting the pair from the airport in a white van, which was later found splattered with the couple’s blood.

A friend of MacGowan testified that MacGowan turned up at his apartment in the early hours of July 6, 2012, covered in blood.

MacGowan’s claim that a third party killed the couple was “utterly fanciful” and it was unbelievable the accused tried to say Mr Maitland was somehow involved, the judge said.

Mr Maitland and Ms Masonwells married in 2009 and moved to Mount Isa from Cairns the following year to work at the mines.

In her victim impact statement, Mr Maitland’s mother, Marjorie, said: “When we finally got the news Cindy and Scott were dead, we thought our lives had hit a brick wall.

“It was so overwhelming we couldn’t absorb the magnitude of the evil, violent crime.”

She also spoke of the heartache of having to watch her grandchild, Scott Maitland’s child from a previous relationship, grow up without a father.

Ms Masonwells’ stepfather and mother, Terence and Sharon Dexter, said in their statement to the court that her death would haunt them until they died.

MacGowan was sentenced to two life sentences with a non-parole period of 30 years.