Three-decade sentence for 'baseball bat' murder

He was given a non-parole period of 21 years and six months during a sentence hearing in the Supreme Court on Friday.

Co-accused Robert Sloan earlier pleaded guilty to murdering Ms Carroll and is due to be sentenced next week.

Namja Carroll's body was found battered and burned at Sandy Point in Sydney's southwest. (Paul Braven/AAP PHOTOS)

Justice Natalie Adams said while it cannot be determined beyond reasonable doubt which one of the men actually killed Ms Carroll, she was satisfied it was Parkes' idea to do so.

"Ms Carroll was beaten to death, her body was set alight," Justice Adams said.

"Although she was probably killed with a baseball bat, there is no direct evidence of that."

The court was also told a tattoo on Ms Carroll's back had been cut off by one of the men.

"It shows the steps taken to cover the murder," Justice Adams said.

During the trial, the jury heard Ms Carroll met Parkes and Sloan when they were selling drugs in Liverpool in the city's southwest.

Ms Carroll had drawn $8500 from her super which she "invested" into their illegal drugs business.

Prosecutors argued that Parkes began to worry Ms Carroll "knew too much" about his drug business and as a result, agreed with Sloan to kill her.

Giving his version of events, Parkes claimed he didn't intend to kill her, saying he only wanted to burn her car because he was paranoid it could be linked to their drug activities.

The ex-Rebels bikie said that when he arrived at Sandy Point he saw Sloan bashing Ms Carroll with a baseball bat.

This claim was rejected by the jury and Parkes was found guilty of murder despite defence barrister Nathan Steel disputing his client inflicted the fatal injuries.

Justice Adams also considered Parkes' psychologist report diagnosing him with ADHD and social personality disorder but questioned whether these mental illnesses could be linked to the crime after CCTV revealed Parkes' "excessive" ice use.

Sloan will be sentenced next Friday at the same court.