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Man must spend 14 years in jail for ex-partner's murder

A seven-year-old boy waited to be collected from school as his aunt found his mum's body in a bathtub.

More than 10 years later, his father has been sent to jail for the "extreme case of domestic violence," killing his partner for fear of losing his children.

The 53-year-old in February pleaded guilty to the 2012 murder at Lithgow west of Sydney.

The couple, who AAP has chosen not to name, parented two children together during their on-and-off relationship before officially separating in 2011.

NSW Supreme Court justice Peter Hamill said their relationship had been fraught but never physically violent until the day he killed the 27-year-old woman.

"(He) was possessive, regularly intoxicated and often verbally abusive ... but until the day of the murder he had not been physically abusive," he said during Friday's sentencing.

Judge Hamill did not believe the murder was planned, but was satisfied the man had formed an intention to kill and was motivated by "his love of his children and fear of losing them".

The judge called it an "extreme case of domestic violence" before sentencing the killer to 19 years and nine months in prison, with a non-parole period of 14 years and six months.

The man used a rectangular object, possibly a piece of wood, to strike his victim, and then maybe a hammer for a "ferocious" blow to the back of a head.

The victim suffered a depressed skull fracture with 10 skull fragments embedded in her brain.

The killer returned to work, nervous and jittery, before his son's school called to report the child had not been collected.

The woman's sister received the same call and immediately knew something was wrong.

She drove to the Lithgow home to investigate and found her sibling in the bathtub.

For eight years, the woman's family waited for a breakthrough in the investigation, which came when DNA evidence allowed police to arrest the man in 2020.

He showed no emotion as the judge outlined the sentence, while the woman's family cried.

The murderer had grown up surrounded by family abuse from his adoptive mother, sister and a Catholic priest, which Judge Hamill said contributed to the offender's later reliance on drugs.

He had injected amphetamines before the murder, but Judge Hamill noted there was "no direct evidence between the history of dysfunction, abuse and neglect, and the killing".

"His moral culpability is reduced to some degree, but those events do not reduce the severity of the crime," the judge said.

Justice Hamill believed the man had reasonable prospects for rehabilitation and was unlikely to reoffend given a lack of significant criminal history.

He will be eligible for parole in 2034.

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