Teenager Larissa Beilby was not murdered and instead died as a result of "misadventure", lawyers for accused killer Zlatko Sikorsky say.
Mr Sikorsky, 34, has been charged with murdering the 16-year-old, after her body was discovered in a barrel south of Brisbane on Wednesday.
He was tracked to the Sunshine Coast and kept police at bay during a 27-hour standoff, eventually surrendering on Saturday night.
It is understood Mr Sikorsky's legal team will argue Larissa died as a result of a tragic accident, and will claim her death was not caused by drugs.
"I absolutely believe he's innocent, and I've been doing this a long time," Mr Sikorsky's lawyer Brendan Ryan said.
"I think that when [the police] have done their job … they will discover he didn't commit the murder.
"If they dot their Is and cross their Ts they will discover that he didn't do anything and rather she may well have passed through misadventure."
While detectives are confident they have enough evidence to charge Mr Sikorsky with murder, it could take months for them to compile a brief of evidence detailing their theory of what happened to Ms Beilby.
Scientific tests have confirmed Ms Beilby was the person found in a barrel at Buccan, but detectives are waiting on results to show a cause and time of death.
Toxicology reports that could shed light on whether Ms Beilby had drugs or alcohol in her system are yet to be received.
Security footage from the Buccan property where Mr Sikorsky was staying will also be reviewed.
It is understood police have been inundated with information from the public in the last week, and are trying to piece together details about the "relationship" between Mr Sikorsky and the teenager half his age.
Ms Beilby was last seen alive on June 15 at a halfway house for runaways in the Brisbane suburb of Sandgate. Police said she made a social media post three days later.
Homicide Detective Damien Hansen said it was "certainly a concern" police were not notified the school student was missing until June 26 — a day before detectives discovered the body.
"Other areas — whether it be schools, other government departments … I won't comment on their processes. We're looking at our processes," he said.
A Government spokesman said nobody by the name of Larissa Beilby was known to the Queensland Department of Child Safety, meaning she was not in state care and had not been the subject of a report to the department in the last 12 months.
On Sunday, Premier Annastacia Palaszczuk congratulated police on making an arrest but said she would not comment on other aspects of the case.
Hundreds of tributes have poured in online for Larissa, with an online fundraising page set up to collect money for funeral costs raising more than $5,000.