Exactly three years to the day that Sydney mother Kristi Abrahams and her boyfriend dragged the body of her six-year-old daughter Kiesha into the bush and buried her in a shallow grave, she has been sentenced to a minimum of 16 years for murder.

Supporters of the murdered six-year-old shouted abuse as Abrahams was taken down to the police cells for the last time, but the 30-year-old showed no emotion.

Outside court, many of the same supporters branded the sentence a "cop-out".

But in handing down his decision, Justice Ian Harrison said that the sentencing process had to be carried out "dispassionately" not by "commentary or opinion ... unchecked by legal principal".

He said the murder, in which Abrahams delivered a number of blows to the young girl's head and then failed to call an ambulance, was the outcome of the abuse the mother herself suffered as a child, and the failure of the system to provide proper care.

"There is a tragic and terrible redolence in the present case with the offender's own unfortunate and frightening childhood," the judge said, referring to Abraham's abuse at the hands of her father, and placement in a series of inappropriate foster and group homes.

"The death of the deceased is the foreseeable and predictable consequence of preventable, cyclic abuse," he said. "The offenders' failings are mirrored in the failings of others."

The acknowledgement of this abuse, along with Abrahams' intellectual disability, was crucial to the length of the jail term, with the judge finding that they represented a "strong subjective case" that mitigated the sentence.

Also crucial to the decision was the finding that while Abrahams had intended to cause "serious injury" to Kiesha, there was insufficient evidence to find that she had intended to kill her.

"The offence was not premeditated ... but a spontaneous act of violence and anger," Justice Harrison said.

He also found that there was insufficient evidence to prove that the severe and repeated abuse Kiesha suffered in the months and years before her death had been inflicted by Abrahams.

This was despite the evidence of two incidents of abuse by Abrahams which were reported to Community Services some years before her death.

Nevertheless, the judge said the murder was a "breach of trust" having been inflicted on "a child in the offender's care, who was entitled to expect care and protection".

He sentenced the 30-year-old to a maximum sentence of 22 years for her crimes, which included disposing of Kiesha's body after her death, with a minimum non-parole period of 16 years.

The sentence drew an angry reaction from a large group of Kiesha's supporters who packed the courtroom.

"Does having a bad upbringing and abuse give you the right to go and take people's lives?" asked one of the group, Alison Anderson.

"She knew what she was doing. It's just a cop-out. Kiesha was killed by a cold-blooded murderer."

Ms Anderson said Kiesha had been let down by the Department of Community Services, which had failed to effectively intervene in the case, and that her group would now be launching a campaign for improvements to the system.

The officer in charge of the investigation into Kiesha's death, Russell Oxford, declined to comment on the length of the sentence handed down, but said he hoped it would make people "take stock".

"If nothing else comes out of today, we should all take stock of where we are in this world and go home and hug our kids."

The sentence brings to a close a case that has refocused attention on the failures of the system of child protection in NSW.

Abrahams beat her daughter to death sometime in mid-July 2010 and then allowed the little girl to die by failing to call an ambulance or provide any medical care.

A few days later, on July 18, 2010, she and her partner, Robert Smith, dragged the little girl's body, which had been placed in a suitcase, into the bush and buried her.

Two weeks later she made a frantic triple-0 call, claiming that her daughter had gone missing that morning.

The call sparked a major search by hundreds of police and SES volunteers, spurred on by Abrahams' public, emotional pleas for help.

"If anyone has seen her can they please contact the police," the then 27-year-old said of her missing six-year-old. "She's beautiful ..."

Scores of locals held candlelit vigils outside the family's Mt Druitt home in front of a make-shift tribute made from soft toys, flowers and heartfelt messages.

But within 24 hours, police discovered the curly-haired little girl had not been seen at school or by anyone else since early that July, and suspicion quickly focused on Abrahams and her boyfriend, Robert Smith.

It took a meticulously planned, nine-month police investigation including undercover officers and hidden surveillance to draw a confession from the couple, leading to their arrest and the discovery of Kiesha's remains in a shallow bushland grave in Shalvey, on what would have been her seventh birthday.

It was another two years before Abrahams pleaded guilty to murder, on what was to have been the first day of her murder trial in June this year.

During this interval her ex-partner, Robert Smith, pleaded guilty to manslaughter and accessory to murder and was sentenced to a maximum of 16 years' jail.

Many of the horrific details of the crime emerged during Smith's sentencing, including that on July 18, 2010, he and Abrahams had kept Kiesha's body in a suitcase for over a week, before they dumped it and set it on fire.

They later bought children's toys and a poster to make it look like the little girl was loved and still alive.

But it wasn't until Abrahams' Supreme Court sentencing hearing that the full, tragic details of Kiesha's short life emerged, along with the failures of the state's child protection system to help.

The little girl's remains exhibited 10 separate bone injuries, indicating repeated blows over the course of months that an expert pathologist said would have left her in "considerable pain".

Kiesha's resemblance to her biological father, Chris Weippeart, reportedly "annoyed Ms Abrahams and triggered her physical and verbal abuse".

"These types of injuries are mainly found in children who have suffered severe, prolonged physical abuse," Dr Matthew Orde said.

It then emerged that community services workers, teachers, police and relatives of six-year-old Kiesha Weippeart all knew or suspected she was suffering serious abuse in the months before her death, but there was no effective intervention before her mother murdered her.

In distressing revelations that highlight serious failures within the child protection system, court documents revealed that, having been placed in foster care after her mother bit her, community services workers learnt Kiesha was burnt with a cigarette soon after returning to the family home, but little was done about it.

A social worker arrived a day after the cigarette burn was reported to find the little girl dressed in a hat and reluctant to show her face.

When asked about the burn, the then three-year-old said, "Mum hit there" and "Mum did that".

Despite this, no further action was taken.

The revelations reignited debate about the huge proportion of child abuse cases that are reported to community services but are never investigated because there are simply not enough case workers and other staff to meet the demand.

Community Services Minister Pru Goward placed responsibility for the failure to intervene in Kiesha's case firmly at the feet of the previous Labor government, which was in power at the time, and rejected claims by the Public Service Association that her government had made further cuts to case workers.

It then emerged that Abrahams herself had been the victim of abuse and had been failed by the system when she was a child, an experience which, her defence barrister said, had contributed to her crime.

"It's easy to hate Kristi Abrahams," Janet Manuell, SC, told the NSW Supreme Court during the final day of the 30-year-old's sentencing hearing.

"It's very confronting for a community to accept the death of a child at the hands of a mother. But Kristi Abrahams is very much a product of what happened to her. She didn't receive the care she needed and that was a failure of the system."