Teen's suspicious drug death referred to cold case cops

His death, from an apparent drug overdose, was not initially treated as suspicious due to his history with substance use and having recently returned from a residential rehab program.

But since he was found, police have found credible evidence indicating others may have been involved in supplying him drugs which caused his death, the coroner found.

Findings from an inquest into Mr McCullough's death were handed down at the NSW Coroner's Court on Tuesday where his cause of death was determined as "mixed drug toxicity".

The 18-year-old was remembered during the inquest as a bubbly and witty person who enjoyed basketball and computer games.

At the time of his death, he was suffering the combined effects of oxycodone, alprazolam, alcohol and cocaine, Deputy State Coroner Carmel Forbes found.

Judge Forbes said there was consistent evidence Mr McCullough was suffering from an overdose on the night of June 8 at a house away from he was found.

In an attempt to wake him from the overdose, an unknown person gave him cocaine, Judge Forbes said.

"(Mr McCullough) was then moved from the house and down the road into his vehicle ... by the persons who gave him the cocaine," the coroner wrote in her findings.

But she could not determine whether the teenager was moved before or after he died and said any evidence from those who were last with him have not assisted with that fact.

"The persons who were last with (Mr McCullough) have either given no account of what occurred or inconsistent versions of events," Judge Forbes said.

She was only able to find his death had occurred between June 8 and 10 and could not make a finding as to the place or manner of death.

The coroner said it was not appropriate to publish further comment given there is an ongoing police investigation. 

She recommended to the NSW Commissioner of Police that Mr McCullough's death should be referred to the force's unsolved homicide unit.