An inquest has heard there is "no compelling evidence" to suggest Matthew Leveson was killed by his boyfriend Michael Atkins, despite Mr Atkins leading police to the 20-year-old's remains in an unmarked grave at the Royal National Park this year.
On Tuesday, NSW deputy state coroner Elaine Truscott heard final submissions into the death of Mr Leveson, who was last seen leaving ARQ nightclub in Sydney with Mr Atkins, 54, in the early hours of September 23, 2007.
Almost a decade later, in a police interview after being granted immunity, Mr Atkins said Mr Leveson died of an overdose after leaving the club, so he panicked and buried his body.
In a submission to the court on behalf of his family, Matthew's father Mark Leveson rejected that explanation, saying Mr Atkins was responsible.
Mr Atkins had told "substantial and significant lies" to the court, Mr Leveson said, including claiming in 2016 that Matthew was still alive.
"Atkins demonstrates a cold, calculating, self-interested behaviour ... not the actions of a person whose loving partner had just died," Mr Leveson said.
"The depth and breadth of the cover-up are not consistent with an accidental death.
"Matthew Leveson died at the hands of Michael Atkins, most likely by smothering or strangulation."
Mr Atkins, who did not appear at the final day of the inquest, was acquitted of both the murder and manslaughter of Mr Leveson in 2009.
Counsel assisting the Coroner, Tim Game SC, suggested the Coroner deliver an open finding into Mr Leveson's death over lack of evidence.
"There's no compelling evidence, notwithstanding the accounts he's given, that it was an act done by him [Mr Atkins] that brought about the death of Matt," Mr Game said.
There was also no evidence to suggest Mr Leveson died of an overdose, as Mr Atkins had claimed.
The inquest heard Matthew's skeletal remains had a number of marks on them, but some of those were likely inflicted post-mortem as his burial site was excavated.
Mr Game said Mr Atkins engaged in "elaborate subterfuge" to cover up the burial, including telling the Leveson family and police that Matthew was alive.
"Mr Atkins well knew a good deal more about the circumstances, when he himself had engaged in an elaborate subterfuge in the disposal, including lies about what he know about Matt's circumstances, and lies about the disposal of Matt's body," Mr Game said.
Speaking outside NSW Coroner's Court in Sydney, Mark Leveson said his family was hoping an open finding was not delivered, but was expecting "the worst".
"Counsel for the Coroner thinks there's no way of determining that Atkins is involved in Matt's death, he's asked for an open finding," Mark Leveson said.
"We vehemently disagree with that.
"This person has great involvement in Matt's death, as well as, we know, disposing of his body."
Faye Leveson said Matthew was a "beautiful, vibrant boy" who loved life, his family, friends, parties, and family gatherings. Since he disappeared in 2007, the family has not celebrated birthdays, Christmas or Father's Day because they are too painful.
"I know we'll probably get an open finding," Mrs Leveson said, becoming emotional.
"The main thing was we did find Matt, we got him back - well we almost got him back, he's still here in the morgue - we'll still fight for him.
"We know in our hearts who was responsible for it. He buried him, and you don't do that to someone you love. You don't just dump them in the bush in an unmarked grave.
"How much did he really love him? He didn't love him at all. Matt was just an instrument to him, just a throwaway item."