Peter Keeley, 56, was found dead near a beach at Broulee, about 20km south of Batemans Bay in February 2020.

NSW Supreme Court's Justice Michael Walton on Thursday acquitted both, who were 17 at the time of the death, after a judge-alone trial in May.

While the duo contested their murder charges, they pleaded guilty to kidnapping Mr Keeley to assault him and thereby causing actual bodily harm.

The court heard Mr Keeley went to the region to meet one of the accused, who "lured" him from Canberra, after they exchanged messages on dating app Grindr.

While Mr Keeley was on his way, the accused he was to meet conducted an online search for "does holding a metal object in your hand make a difference to your punch?"

The two accused and a third man, also 17 at the time, discussed a plan for them to tie Mr Keeley and assault him.

A witness and authorities discovered Mr Keeley's body with his hands and feet tied, as well as tape near his mouth being torn and removed.

Played during the trial was a recorded police interview with one of the accused who told investigators the trio planned to only scare Mr Keeley "because we were all under the impression he was a paedophile".

The accused said they had "no concrete evidence" about that allegation and "I don't think there was any intention to kill him".

Forensic pathologist Dr Bernard I'Ons, whom the Crown relied on, concluded in his autopsy report that Mr Keeley died from craniofacial trauma and airway obstruction.

The former included widespread abrasion and a fractured nose.

Dr I'Ons said Mr Keeley was concussed and in a prone position that led to asphyxia, contributing to his death.

Other factors for airway obstruction included Mr Keeley being gagged and having debris in his nose.

AS IT HAPPENED

The cause of death, however, was the major contention during trial. Specifically, whether it was from the assault or a possible methamphetamine overdose as the drug was detected in Mr Keeley's system at the time.

The defence argument, based on professor Johan Duflou's evidence, was that Mr Keeley's death "could reasonably be the result of methamphetamine toxicity" as he was a regular user of the drug.

Professor Duflou said the level of methamphetamine in Mr Keeley's system was "pretty much right in the centre [of where you would] expect" in the cases of an overdose.

He agreed that multifocal blunt force trauma was occasioned to Mr Keeley's head but did not believe the injuries were life-threatening.

He also said there was no evidence that Mr Keeley was in a prone position for a long time, as well as no obstruction to airways and no indication of massive bleeding.

Crown prosecutor Nerissa Keay said the duo's assault was the foundational offence to murder.

Ms Keay argued Mr Keeley was "extensively assaulted" with blows to the head.

Justice Walton said the Crown had not proven beyond reasonable doubt that the cause of death was craniofacial trauma combined with airway obstruction.

"It is clear from the cross examination of Dr I'Ons that the autopsy report is predicated on the presence of tape over the deceased's mouth when he died," Justice Walton said.

"The autopsy report thus proceeded on a flawed premise."

He said that once the tape was removed from Mr Keeley's mouth, there was no obstruction and "it follows that his mouth would've been open or able to be open".

The judge said even if one were to accept the Crown's submission that breathing was difficult due to a broken nose Keeley had suffered, he would have still been able to breath through his mouth.

Justice Walton said evidence showed Mr Keeley was concussed at some point, but not for any extended time.

"As professor Duflou opined, given the extent of the injuries found, it was most likely that any unconsciousness would've been for a short period of time or alternatively the deceased would not be unconscious but rather dazed," he said.

In relation to the potential drug overdose, Justice Walton said professor Duflou's views should be preferred based on a number of factors, including that his "eminence on the question of methamphetamine toxicity is well recognised".

He said the Crown had also not excluded the possibility of a drug overdose as the cause of death.

Justice Walton also said one of the accused on trial "was untruthful to the police when he said he played no part in the assault and detention of the deceased".

The two men are scheduled to face court again at a later date related to the aggravated kidnapping.

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