The 47-year-old pleaded guilty in Tamworth Local Court earlier this week to a charge of acting with intent to pervert the course of justice in the lead-up to her murder trial.

Darcy will be sentenced in the district court, though is already serving 40 years in jail for sedating and gassing her Walcha partner, Mathew Dunbar, and staging his suicide in 2017 in an effort to get her hands on his multi-million-dollar estate.

A set of agreed facts tendered to the court reveal 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.

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.

READ ALSO:

"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.

If this story has raised issues for you, or if you or someone you know needs help, please call Lifeline on 13 11 14 or Beyond Blue on 1300 22 4636.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: