Natasha Beth Darcy is behind bars for at least 25 more years but is awaiting sentence for acting with intent to pervert the course of justice.

She did not appear in Tamworth District Court on Monday morning when her case was called but solicitor Tracey Randall said her case was almost ready to go

"It will be a fairly narrow focus," she told the court via video link from her office.

She said the matter was "not a crushing sentence, just [goes towards] specific deterrence".

Darcy, aged 47, pleaded guilty in June to the offence which she committed while in jail in the lead-up to her murder trial in Sydney last year.

Earlier this year, she was jailed for 40 years for sedating and gassing Mathew Dunbar, her then Walcha partner. The jury, and judge, found she had staged his suicide in his bed at his 'Pandora' property in 2017 in a bid to get her hands on his multi-million-dollar estate.

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Ms Randall said Nicholas Broadbent the "public defender is briefed in the matter". Mr Broadbent was on Darcy's legal team for her murder trial.

The court heard the sentence matter would be relatively quick and the "estimate is one hour".

Ms Randall told Judge Andrew Coleman SC that Darcy was already in custody, but not for this matter.

"She's currently serving a very long sentence, Your Honour," she said

"Her non parole doesn't expire until 2047."

"2047?" Judge Coleman replied.

"Yes, Your Honour," Ms Randall said.

In June, the Leader revealed Darcy's last-ditch attempt to get away with murder was to write to a school friend in the months before her trial, offering $20,000 or "as much as you need" for a false statement.

A set of agreed facts tendered to the court when she pleaded guilty showed Darcy wrote in the letter that she'd been watching an episode of Frasier where a character asked another to lie in court because the opposition was using dirty tactics, but it raised a moral dilemma.

"It got me thinking that if only I could ask somebody to say that Mathew told them he was planning his suicide, maybe a few or several days before he passed," Darcy wrote.

"I'm going to make you a proposition and see if you can be the one to help me."

Darcy wrote a list of details she thought would be sufficient, asking the woman to tell police she spoke to Mr Dunbar for about 40 minutes and that he had said he was planning suicide and had been researching methods.

Darcy wrote that all detectives had on her were extensive web searches and that once someone confirmed Mr Dunbar had been planning suicide, "they have nothing".

She added that friendship was the most important thing and there was no pressure to agree.

The first letter was written in early January 2020 - just months ahead of Darcy's original trial date before it was delayed due to COVID - and was followed by a second letter later that month.

In that note, Darcy wrote she was reminded of a "funny saying" which she recalled went something like "if you're ever in trouble I won't be there to support you, 'cause I'll be next to you helping you hide the body".

The woman received both letters but never replied or spoke about them with Darcy, the agreed statement shows.

She remained tight-lipped on the letters for more than a year but phoned the state prosecuting authority, the DPP, after she saw in the media that Darcy's murder trial had started.

She ultimately gave evidence for the Crown in the trial, which ran for 10 weeks in the NSW Supreme Court in Sydney in 2021.

Both letters were tendered to the court during the trial and their confronting contents were reported at the time.

Tamworth detectives later charged Darcy with acting with intent to pervert the course of justice.

Darcy will be sentenced in September.

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