A 14-year-old boy found her skull in a dried up creek bed in 2018.

French was jailed for at least 10 years after pleading guilty over her death and the disposal of her body in November 2021.

He was already in custody when Brown came forward, telling police he thought it was the right thing to do.

He had thought about the incident ever since but not spoken to anyone about it.

Brown was hanging out with his cousin French, doing ice, drinking at the pub and playing pokies on the day French assaulted Ms Ardler in the street before striking her in the head and killing her in a bedroom of their home at Cranebrook in Sydney's west.

After Brown went into the bedroom, French said he did not want her body there anymore, and told Brown to help him carry her about 750 metres into bushland.

Despite French being jailed over the killing, police had no evidence of Brown's involvement before he came forward.

The delay in disclosing his brief and unsophisticated involvement in disposing of the body meant Ms Ardler was not found for more than five years, Judge Huw Baker said, sentencing Brown in the NSW District Court.

"His acts contributed to a teenage boy discovering the skull of the deceased which must have been traumatic for him," the judge said on Friday.

But he found Brown remorseful, with clear evidence he had accepted responsibility for his actions and acknowledged the harm they caused.

Brown was sentenced to one year and 11 months in jail, with a non-parole period of one year and three months.

He went into custody after admitting his role in disposing of Ms Ardler's body to police in December 2022, meaning his non-parole period expired on Tuesday.

His full sentence expires in November.

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