A MYSTERIOUS "potentially lethal" drug dose is among the issues a defence lawyer says jurors need to consider after the death of Scott Frank Williams.
But a prosecutor says a vicious, unnecessary attack by Brandon John Mischewski is the reason Mr Williams died.
Mr Mischewski pleaded not guilty last week to unlawful striking causing the death of Mr Williams.
He also pleaded not guilty to the alternative charge of unlawfully killing Mr Williams, who died at a unit in Buddina in January 2016.
Closing the Crown case on Thursday, prosecutor Phil McCarthy said Mr Williams tried avoiding the attack.
He told Brisbane Supreme Court Mr Mischewski was not acting in self-defence but was the attacker.
He said there was "no reasonable basis" Mr Mischewski could believe "stomping and punches" he inflicted were reasonable.
"All he had to do was stop. Stop attacking Mr Williams."
Jurors earlier heard Mr Mischewski told a covert police operative: "I punched someone the other day and they died."
Mr McCarthy earlier said Mr Williams died after receiving a large fracture to the left side of his skull.
Defence counsel Eoin Mac Giolla Ri said another man's involvement at the unit was crucial, as were drug traces found in Mr Williams's system.
The defence barrister said a "potentially lethal" amount of methamphetamine was found but no evidence explained who administered this dose.
He said Mr Mischewski was not that person.
"Why give someone that amount of methamphetamine?"
"We don't know, but we know someone put that in his body."
He said there was no explanation how Mr Williams - who'd been a user of a different drug, the opioid fentanyl - ingested this drug.
He also asked jurors to consider if another man who testified seeing a fight at the unit "applied the force" pivotal to Mr Williams's injuries.
"If it wasn't the force from [Mr Mischewski] which caused these injuries, he is not guilty on every view."
He said a witness who admitted his "own mother would close the door in his face" testified against Mr Mischewski and was a "terrible liar".
Mr Mac Giolla Ri said that witness provided two different stories.
One involved "a bit of a punch-up, a struggle, a scuffle and a slip".
He urged jurors to consider if that was true.
"Or was it the version where Mr Mischewski stomped on his head?"
Justice Ann Lyons was expected to sum up the case after the defence closing.
The jury was expected to go out on Friday. -NewsRegional