Benjamin Troy Parkes, 46, was found guilty of violently murdering Namja Carroll with his co-accused Robert Sloan on July 14, 2020.
The 33-year-old's body was then doused in petrol and set alight before being discovered by a bushwalker hiking through the area at Sandy Point, in Sydney's southwest, 15 days later.
At a sentence hearing on Tuesday, NSW Supreme Court Justice Natalie Adams noted a psychologist's report diagnosing Parkes with ADHD and a social personality disorder.
But she questioned whether these mental conditions could be linked to the crime at all, adding CCTV footage revealed the ex-bikie engaged in "excessive" use of ice that impaired his judgment at the time.
"He clearly wasn't getting any sleep - he was taking a lot of ice," she said.
During the trial, the jury heard Ms Carroll met Parkes and Sloan when they were selling drugs out of Hunts Hotel Liverpool, also in the city's southwest.
Ms Carroll had "invested" $8000 in their illegal drugs business by drawing from her superannuation, jurors were told.
Prosecutors argued that Parkes was worried Ms Carroll "knew too much" about his drug business and formed an agreement with Sloan to kill her.
The pair arranged to take her to an acquaintance's house in Smithfield, where she stayed in his garage before being taken to the Sandy Point bushland to be killed.
Parkes claimed he did not intend to murder Ms Carroll, saying he only wanted to set fire to her SUV out of concerns it could be linked to the drug business.
He said he arrived at Sandy Point to see Sloan brutally bashing the 33-year-old woman with a baseball bat.
The jury rejected these accounts in finding Parkes guilty of murder.
On Tuesday, defence barrister Nathan Steel still disputed that his client was the one to inflict the fatal wounds.
He also argued that the intention to kill Ms Carroll might not have been made at the time she was removed from the Liverpool hotel.
"Clearly at least by the day that the murder occurred, the agreement had been reached," he said.
Parkes' claims the murder occurred quickly after arriving at the bushland was contradicted by cigarette butts found near the site of the bashing.
One of these tested positive for Ms Carroll's DNA, showing she had time to stop for a smoke, Justice Adams said.
Forensic evidence the victim received three blunt-force injuries before being killed was also inconsistent with Parkes' claims he had seen Sloan beat her 20 times with the bat, crown prosecutor Darren Robinson argued.
Justice Adams will sentence Parkes on July 26.
Sloan will face his own sentence hearing over the murder on Friday.
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