Meth overdose possibly killed Canberra auctioneer Peter Keeley, NSW Supreme Court told

Peter Keeley, 56, was found dead in February 2020 after chatting with a 17-year-old boy on gay dating app Grinder.

Two teenagers have pleaded guilty to the aggravated kidnapping of Mr Keeley, but they say they did not murder him.

Their lawyers argue he may have died due to methamphetamine toxicity.

During closing submissions in a NSW Supreme Court trial on Monday, defence barrister Clive Steirn SC attacked evidence given by forensic pathologist Dr Bernard l'Ons, saying there were "major problems" with his autopsy report and describing his "conflicting" evidence as a "comedy of errors".

Mr Steirn said while Dr l'Ons had been a forensic examiner for just six years, fellow witness Professor Johan Duflou had more experience, published research papers and had a "special interest in methamphetamines".

"[The] comparison between Dr Duflou and Dr I'Ons speaks for itself," Mr Steirn said.

Dr l'Ons said last week he was cautious of saying Mr Keeley died from methamphetamine toxicity because the alleged murder victim did not have a history of heart disease.

Mr Steirn said Dr l'Ons' responses to questions on the topic were "troubling" and displayed an "unwillingness to follow his own practice", while Professor Duflou's remarks - which did not rule out a drug-induced death - were considered and showed "nuanced insights".

Mr Steirn quoted Dr Duflou as saying 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.

Professor Duflou had also previously said the cause of death "could reasonably be the result of methamphetamine toxicity".

He did not believe Mr Keeley's injuries were life-threatening, saying there was no obstruction to airways or indication of massive bleeding.

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Crown prosecutor Nerissa Keay has argued Mr Keeley died from head injuries.

Dr l'Ons' autopsy report concluded the auctioneer's cause of death was craniofacial trauma with obstruction of airway.

The forensic pathologist said an instrument may have been used on Mr Keeley, leading to a "significant injury to the brain".

Justice Michael Walton is now considering his verdicts in the judge-alone trial.

A third teenager, who has also been charged with murdering Mr Keeley, will face a separate trial at a later date.

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