Court hears Morcombe accused 'confession'

"Yeah ok ... yeah I did it."

Daniel Morcombe's accused killer thought he was confessing his "deepest, darkest secret" to an underworld crime boss.

But it was actually an undercover police officer who heard Brett Peter Cowan describe how he murdered the 13-year-old Queensland schoolboy.

Video and audio recordings of the 2011 confession were played to the jury at Cowan's murder trial on Thursday.

In them, he describes abducting Daniel from the side of the road and later choking him to death in a panic.

Cowan told undercover police he offered the teen a lift to a shopping centre but instead drove him to an isolated, abandoned house in the Sunshine Coast hinterland.

"He came inside and I went to pull his pants down. He panicked and I grabbed him," Cowan can be heard saying in one recording.

"I never got to molest him or anything like that.

"He panicked and I panicked and grabbed him around the throat and before I knew it he was dead."

Daniel's parents Bruce and Denise Morcombe watched from the public gallery while the video and audio recordings were played to the court.

In the video Cowan can be seen demonstrating with his own arm how he put the teen in a choke hold.

"There was no screaming or nothing," he said.

He described how he drove the teen's body 150 metres to an overgrown former sand mine and threw him down an embankment.

He stripped him and covered him with trees and branches before tossing the clothing in a creek, the court heard.

He returned about a week later and found only a fragment of bone, which he destroyed with a shovel.

In one conversation Cowan expressed regret over the "spur of the moment" decision to abduct Daniel, made on his way home from picking up a garden mulcher.

"If I was 10 minutes later getting the wood chipper I wouldn't have seen him," he said.

"... It's only because he struggled and I panicked, otherwise he would still be here today."

The confession was the culmination of an elaborate undercover operation by West Australian police, the court heard.

Officers posing as criminal gang members spent more than four months convincing their target they were part of a powerful underworld organisation.

Cowan was led to believe he could earn $100,000 in a drug deal but there was a catch - the gang had information he murdered Daniel Morcombe.

The gang's "big boss" met Cowan in a Perth hotel room and told him he'd be dumped "like a hot potato" unless it could be sorted out.

Cowan insisted police couldn't "pin it on me" because he'd told no one else his "deepest darkest secret" and there was no forensic evidence.

Undercover police arranged to return with Cowan to the alleged crime scene under the pretence of cleaning up evidence.

Cowan said he didn't know whether returning to the crime scene would give him "the heebie jeebies".

Cowan, 44, has pleaded not guilty to murder, indecent treatment of a child and interfering with a corpse.

The trial continues.