'My baby': allegedly murdered surrogate wanted child

A man would have sex with an intellectually disabled teen "all the time" before impregnating and allegedly killing her in order to keep the baby, a court has been told.

The man and his wife, now aged in their 60s, are standing trial in the Supreme Court in Wagga Wagga after both pleaded not guilty to murdering the 19-year-old.

On Tuesday, the trial heard from a relative and sometimes guardian of the teen, who lived next to the couple on a property in rural NSW.

In late 2000, the girl 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 relative said the teen had told her the man's wife was unable to have a baby and wanted her to have one for the couple to keep.

"But she said 'no'," the woman told the court.

"She said 'I don't want to have a baby for anyone'.

"She said, 'it's my baby'."

Once the teen gave birth to the baby, the relative told the court she would not have left it in the care of anybody else.

"She loved (the baby)," the woman said.

The relative said while living with the couple, the pregnant teen looked "dirty and unhealthy".

She said on one occasion she picked the girl up and she could tell she was hungry and had lost weight.

"She was starving," the woman told the court.

The court was also told at the age 14, the girl had fallen pregnant to her cousin and that the pregnancy was terminated.

The teen was last seen at her flat in a nearby rural town on June 2, 2002, and a police investigation was launched into her disappearance, with the couple, who cannot be named for legal reasons, eventually charged with murder in May 2022.

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.

He asked the relative how often the man would have sex with the teen.

"She told me she used to have it in the car, she used to have it all the time," the relative said.

"She used to kind of laugh, like laugh about it.

"I said 'don't laugh about it'. I said 'that's no good'."

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 prosecutor argued against 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.

The trial continues.