A witness to events before an alleged murder where two people were locked in a toolbox and drowned has admitted to a jury he lied to police.

Stou Daniels, Davy Malu Junior Taiao and Trent Michael Thrupp are charged with murdering Cory Breton, 28, and Iuliana Triscaru, 31, at Kingston in Logan, south of Brisbane, on January 24, 2016.

Lelan Harrington, a former flatmate of some of the defendants and friend to the alleged victims, agreed under defence cross examination in the Queensland Supreme Court that he lied to police about Breton owing money to Daniels.

Daniels’ defence barrister John Fraser asked Harrington today if he had told a “massive lie” to police when he made a statement that Daniels was present at the lagoon when the toolbox containing the alleged victims was thrown into the water.

“It was a lie. Not a massive lie,” Harrington said.

Fraser asked if Daniels would have told a “huge lie” if he hypothetically said to police Harrington was present at the alleged murder scene.

Harrington had earlier testified Thrupp told him he had killed Breton and Triscaru.

“I asked him what it was like,” Harrington said.

“He said ‘I opened the toolbox and they begged for their lives’ and he shot them in the head.”

Harrington said Thrupp told him he put holes in the toolbox to make it sink and then weighed it down with tyres and pieces of concrete.

The bodies of Breton and Triscaru were found in the toolbox at the bottom of Scrubby Creek two weeks after they were allegedly murdered.

Crown prosecutor Nathan Crane previously told the jury they would hear forensic evidence the pair likely died from drowning but their remains were too decomposed to be certain.

All three defendants pleaded not guilty to two murder charges at the start of their trial on Monday.

Crane said the prosecution would allege Thrupp was present with another man at Scrubby Creek when Breton and Triscaru were locked in the toolbox and thrown into the water.

Daniels, Taiao and Thrupp were accused of going to a multi-storey residential unit where Breton and Triscaru were tied up, assaulted and tortured in the hours before they died.

Harrington said he had been living upstairs at the unit when the defendants lured the pair inside because they thought Breton might be a “dog” by informing police about their drug dealing.

“I could hear the duct tape. I heard the hit. Everyone jumped on him,” he said.

Under cross-examination, Harrington admitted he was high on methamphetamine when the alleged victims arrived and was later convicted of assault occasioning bodily harm and deprivation of liberty for assisting in their violent interrogation.

Harrington said he later went downstairs to see Breton and Triscaru sitting on a couch in the living room while bound with cable ties and duct tape.

“(Breton) had a stab wound above his front knee. I could see the blood,” Harrington said.

The jury heard Triscaru started “hyperventilating” when Harrington helped carry a two-metre-long toolbox into the living room.

“That’s when (Triscaru) started freaking out. Cory sat there numb,” Harrington said.

The jury heard Taiao hit the alleged victims in the head to get them to lie down head-to-toe in the toolbox, which was carried to the back of a HiLux utility vehicle.

“(Daniels) stood there giving the orders … (Breton and Triscaru) were banging and screaming pretty loud,” Harrington said.

“We had the music in the car turned up to the max.”

Harrington said he did not go in the HiLux to the creek and instead helped clean bloodstains in the unit.

The trial continues before Justice Glenn Martin.