Two men accused of murder by drowning two people in a toolbox thought they were part of a non-fatal "boot ride" punishment common among drug dealers, a jury has heard.
A third man accused of the double murder would be placed at the scene by witnesses who received reduced sentences, the jury also heard.
Stou Daniels, Davy Malu Junior Taiao and Trent Michael Thrupp are charged with murdering Cory Breton, 28, and Iuliana Triscaru, 31, south of Brisbane on January 24, 2016.
Police divers found the bodies of Mr Breton and Ms Triscaru in the box at the bottom of a lagoon two weeks later.
All three men pleaded not guilty to two murder charges at the start of their trial in the Queensland Supreme Court.
John Fraser, defence barrister for Daniels, told the jury during his opening address on Tuesday that his client thought he was taking part in a "boot ride", a common event in the world of drug users and dealers.
"It is where someone is put in the boot of a vehicle and given a scare and then let go," Mr Fraser said.
"This had all the hallmarks of a boot ride."
Mr Fraser said Daniels left the scene before Mr Breton and Ms Triscaru were taken in a toolbox on the back of a HiLux and subject to a "truly shocking" alleged murder.
Prosecutor Nathan Crane previously told the jury the alleged victims, who were "good friends" were likely thrown into a nearby Scrubby Creek while still alive and trapped in the toolbox.
Mr Breton and Ms Triscaru had earlier been lured to a residential unit at Kingston, south of Brisbane, and were tortured before being forced into a large toolbox, Mr Crane said.
Mr Fraser told the jury they would not hear any evidence Daniels went to the creek.
Lars Falcongreen, defence barrister for Taiao, told the jury the "real battleground" for his client at trial was allegations he knew about any plans to kill.
Mr Falcongreen denied claims Taiao would have known death was a probable consequence of the alleged victims being put in a toolbox.
"It is a bit of a stretch that somebody would go down this homicide road when there was a plan to scare the hell out of (Mr Breton and Ms Triscaru)," he said.
Mr Crane previously told the jury Thrupp was allegedly at Scrubby Creek and either personally threw the toolbox into the water or was party to doing so.
Jessica Goldie, defence barrister for Thrupp, said it was not an issue that her client was at the Kingston unit, but claims he had the intent to kill would be contested.
"What happened at Scrubby Creek is really not clear. There is no definitive cause of death," she said.
Ms Goldie said witnesses who were due to testify against Thrupp had received " significant benefits" in their sentences for giving evidence.
"Are they credible? Are they trustworthy? Are they reliable?" she told the jury.
The trial continues before Justice Glenn Martin.
