A couple's repeated failures to have children led to the man impregnating an intellectually disabled teen and then jointly planning to murder her with his wife to keep the baby, a court has been told.
The couple lived on a rural NSW property neighbouring where the young girl lived on and off with her extended family.
In late 2000, the teenager moved onto the couple's property and formed a sexual relationship with the then 40-year-old man, becoming pregnant and having a child.
The 19-year-old was last seen at her flat in a nearby rural town on June 2, 2002, and a police investigation was launched into her disappearance.
The couple, who cannot be named for legal reasons, were eventually charged with murder in May 2022 and are facing trial in the NSW Supreme Court.
Each pleaded not guilty as a three-week judge-alone trial started on Friday.
Crown prosecutor Paul Kerr said the alleged murder victim had been diagnosed with an intellectual disability that limited her capacity for speech, literacy and general cognitive function.
Medical experts and family described her as someone with the mental capacity of a 12- or 13-year-old who could be easily led by others, he said.
In 2001, after the teen fell pregnant to the husband, a social worker expressed concern that she was living in an unsafe environment and had been used for sexual purposes to be a surrogate mother.
The pregnancy came after the wife experienced three miscarriages and one still-birth after her first child was born, Mr Kerr said.
"It was always the intention of the (couple) to assume the custody and care of (the baby)," he told the judge.
"They knew that to do that (the alleged victim) had to be removed from the equation."
In June 2002, the teen was told her father was dying in a Sydney hospital.
She was last spotted at her apartment on June 2 and had not been seen or heard from since, Mr Kerr said.
The prosecutor rejected the couple's claims they had dropped the teenager without her baby in Sydney on June 5 to visit her father.
They took 14 days to report her missing to police and made no attempt to contact her or try to ascertain her whereabouts during that time, he said.
Conversations captured by covert listening devices installed in their home and car pointed to an "almost certain involvement" in the young woman's disappearance and murder, Mr Kerr said.
He said it was a "strands in the cable" case against the pair that was largely, if not entirely, circumstantial.
But Mr Kerr said the couple should still be found guilty of murder as part of a joint criminal enterprise to get rid of the teenager.
The wife's defence barrister, Michael King, said there was no dispute the husband had impregnated the teen, but he argued their home was a safer environment for the vulnerable woman than with her own family next door.
The woman did not kill the 19-year-old and there was no agreement for her murder, her barrister said.
Searches of the couple's property, local dams and even an investigation sparked by a psychic did not turn up any evidence against the couple, Mr King added.
Because of the husband's unfortunate history with law enforcement, police were eager to include the couple as prime suspects in the woman's disappearance and build their case on this assumption, he said.
The husband's barrister, Paul Coady, agreed, saying the evidence against the couple consisted of reconstructed events that were now remembered as sinister but were anything but.
The alleged motive of wanting the baby for themselves was also "self-destructive", he said, because the child was already in their lives.
The act of murdering the teenager would also have seen the baby swiftly removed from their care at even the faintest of suspicions, Mr Coady said.
The trial continues.
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