A key witness in the double murder trial of Queensland mechanic Brandon Peter MacGowan turned up the volume on his video game to drown out screams coming from outside, the Supreme Court has heard.

MacGowan, 43, is accused of killing Mount Isa couple Scott Maitland and Cindy Masonwells in July 2012.

The Crown alleged the couple had flown to Cairns to pick up their panel van they paid MacGowan $14,000 to restore.

But when they arrived, the van was not fixed and MacGowan allegedly murdered them.

Mr Maitland was shot once in the back of the head and Ms Masonwells was stabbed to death.

MacGowan denies the charges.

Witness Brendon Lubbers-Mott, who lived in a Cairns industrial estate, saw a man pull a woman out of a van by her arm in early July 2012.

The woman was screaming and told the man to "f*** off", Mr Lubbers-Mott said.

The man then came over to Mr Lubbers-Mott and said: "Hi, I'm Brando. Stay out of it", the court was told.

Mr Lubbers-Mott, 21, was then escorted back inside his accommodation and his roller door was pulled down.

He then went back to playing his PlayStation.

"I heard a bit more screaming so I turned up the TV a bit more," Mr Lubbers-Mott said.

After the van had left, Mr Lubbers-Mott went outside and noticed the ground had been hosed down.

Mr Maitland's and Ms Masonwells's decomposed bodies were found in scrubland near Cairns later that month.

MacGowan was 'streaked' with blood: witness

MacGowan and his car were covered in blood on the night the victims disappeared, a friend of his told the Supreme Court on Tuesday.

Daniel Curtis said MacGowan has visited him at his hotel apartment shortly after midnight and said he had been in a fight.

MacGowan was "streaked" in blood and Mr Curtis said he helped dispose of the incriminating clothes.

The next day Mr Curtis noticed blood over the front passenger door of MacGowan's white van, and was asked to clean it off.

MacGowan also asked if he could keep the van in the hotel carpark for a few days.

Under cross examination, defence barrister Joshua Trevino disputed claims MacGowan's clothes had blood on them and showed footage of him entering the hotel.

Mr Trevino asked Mr Curtis where the blood was and accused him of providing confusing evidence.

White van owned by workshop customer

MacGowan picked up the couple from the airport in a white van when they arrived on July 5, the court was told.

It was found a week later by police at the Commonwealth Bank carpark in the Cairns suburb of Westcourt.

There was a large amount of blood inside and a spent cartridge in the back, the court heard.

A photo of a 1975 Holden Sandman panel van, similar to that owned by Scott Maitland and Cindy Masonwells. ( Supplied: Qld Police )

The van was owned by Andrew Grimsley who had dropped it off to MacGowan’s workshop to be serviced a few days before the alleged murders.

When Mr Grimsley rang to collect the van, MacGowan said it had been hit by another car and was at a panel beaters' getting fixed.

Mr Grimsley told the court he did not own guns or ammunition and could not explain how a spent cartridge got in there.

The trial continues.

Editor's note 8/9/2014: This story has been amended to clarify the chronology of events described by Brendon Lubbers-Mott.