Walcha murder: Natasha Beth Darcy denied bail in NSW Supreme Court, charged with murdering Mathew Dunbar near Walcha

No bail: Natasha Beth Darcy-Crossman, 42, inset, is charged with murdering Mathew Dunbar on August 2, at Walcha. Police are pictured searching the property in 2017 following her arrest. Photos: Gareth Gardner, supplied
No bail: Natasha Beth Darcy-Crossman, 42, inset, is charged with murdering Mathew Dunbar on August 2, at Walcha. Police are pictured searching the property in 2017 following her arrest. Photos: Gareth Gardner, supplied

A woman accused of staging the suicide of her grazier partner blended a powerful cocktail of sedatives used to knock him out in a Nutribullet, the NSW Supreme Court has heard.

Natasha Beth Darcy is charged with murdering Walcha farmer Mathew Dunbar in August 2017 by drugging him with a mixture of substances, including a ram sedative, before putting a plastic bag over his head and gassing him with helium in a bid to make it seem as though he killed himself.

Justice Stephen Campbell refused Ms Darcy's application for bail on Thursday, concluding there was a strong Crown case against her.

"It's said it's clear that the ... cocktail I’ve referred to was made putting these drugs into some sort of device referred to as a Nutribullet mixer to blend them and that traces of them were found in an unwashed drinking glass," Justice Campbell said.

"The applicant says that she didn’t make the cocktail."

"The property is one of considerable value. At least ordinary folk not having great personal wealth would think so," Justice Campbell said.

In declining to free her, Justice Campbell said he "could not ignore" Ms Darcy's criminal history, which included being jailed in 2012 for setting her family home alight while her then-husband was asleep inside.

She was initially charged with attempted murder, but that charge was withdrawn.

Justice Campbell said Ms Darcy had separately been imprisoned for dishonesty offences and tried to persuade another partner to change his evidence against her in criminal proceedings by manufacturing counter-charges against him.

Ms Darcy also had a history of using sedatives in the commission of crimes, the court heard.

No bail: Police are pictured searching the property in November 2017 following her arrest. Photos: Gareth Gardner, supplied

No bail: Police are pictured searching the property in November 2017 following her arrest. Photos: Gareth Gardner, supplied

Her barrister, Edward Anderson, said Mr Dunbar had a history of mental illness and had threatened suicide with a rifle in the months before he died, leading him to be prescribed medication that made him susceptible to short-term suicidal thoughts.

"There is a rational hypothesis consistent with innocence in this case," Mr Anderson said.

The court heard Mr Dunbar’s doctor had been treating him for depression since 2009 and that a close friend of his had taken his life in the first half of 2017.

Mr Anderson said that, following Mr Dunbar’s own suicide threat, he was prescribed the anti-depressant Zoloft, which was increased in dosage by his GP in the month before his death.

He was later hospitalised due to an infection on his right leg.

Ms Darcy alleged she went to sleep in a separate part of the home they shared on August 1, waking up in the early hours of the morning because wood burning on the stove had set off the fire alarm.

She claimed that she phoned police after finding Mr Dunbar's body at 2am.

Ms Darcy, who appeared via audiovisual link wearing prison greens, wiped away tears as Mr Anderson said his client had "suffered considerably since that time".

"She was diagnosed with anxiety prior to this event and I understand has been diagnosed with PTSD (post-traumatic stress disorder) since this event," he said.

No bail: Mathew Dunbar. Photo: supplied

No bail: Mathew Dunbar. Photo: supplied

In arguing for her release, Mr Anderson said Ms Darcy was prepared to live at her mother's south coast home, report to police twice a day and wear an electronic monitoring bracelet.

But prosecutor Kenny Ng said there was "great concern" about her interfering with the Crown case if she were to be bailed.

"This applicant has a tendency to fabricate evidence and to effectively come up with or enact very elaborate schemes," Mr Ng said.

In reaching his decision, Justice Campbell referred to evidence of her providing a false name, phone number and address in buying ram tranquiliser from an Armidale vet.

Ms Darcy has alleged her details were mistakenly recorded, the court heard.

"The applicant had initially made inquiries about obtaining the helium tank," Justice Campbell said, adding Ms Darcy and Mr Dunbar picked up the tank together the day before his death.

"It was said that was required for some sort of celebration or function."

The court heard Ms Darcy conducted internet searches using terms such as a "suicide bag", "euthanasia device" and "helium-filled exit bag" leading up to Mr Dunbar's death.

It's also alleged that she sent a text message designed to look like a suicide note from Mr Dunbar's phone on the night of his death.

"The prosecution case is it was the applicant who used the deceased's phone to lay a false trail," Justice Campbell said.

The case will return to the local court this year.