A NSW woman accused of sedating and gassing her wealthy partner in his bed denies murdering the grazier, saying he killed himself.
But Natasha Beth Darcy's numerous internet searches before his death included the phrase "how to commit murder", prosecutor Brett Hatfield said on Wednesday.
The 46-year-old had pleaded guilty to aiding or abetting suicide, but Mr Hatfield told the jury the Crown rejected the plea and contended she killed Mathew Dunbar.
She's pleaded not guilty in the NSW Supreme Court in Sydney to murdering the 42-year-old sheep farmer on his property Pandora in the Northern Tablelands town of Walcha in the early hours of August 2, 2017.
He was found in his bed with a plastic bag over his head, in which was inserted a tube connected to a gas cylinder.
The prosecutor contended Darcy's main motive involved her being the sole beneficiary of the $3.5 million property.
But her barrister Janet Manuel SC told the jury of the grazier's physical health problems, his depression, the suicide death of a very close friend in April 2017, Mr Dunbar's own suicide threat in June 2017 and his admission into a psychiatric unit.
Mr Dunbar did not leave a suicide note, but she expected the jury would hear psychiatric evidence that was "really common".
Mr Hatfield listed many internet searches made over months on various phones and a computer, searches which Mr Hatfield alleged were made by Darcy.
"The accused acknowledges she made some but not all the searches," he said.
"She has suggested the deceased made a number of them."
Search topics included poisonous spiders and mushrooms, toxic plants, suicide methods, how to commit murder and "can police see websites you visit on your mobile".
After the couple had dinner and shared red wine, Darcy allegedly used a Nutribullet to blend sedatives into a drink she gave to her partner in a glass tumbler.
She allegedly later placed over his head a plastic bag connected by a tube to a gas cylinder the couple had bought in Tamworth earlier that day.
Darcy was married to paramedic Colin Crossman, but they had been separated for some time.
At 1.14 am on August 2, Mr Crossman received a text from Mr Dunbar's phone which said "tell police to come to house, I don't want Tash or kids to find me".
Darcy rang triple zero at 2am saying she had discovered her partner in his bed with a plastic bag over his head and gas or something going into it.
Mr Hatfield said Darcy "exploited" Mr Dunbar's depression to kill him in a way to make it look like suicide.
Mr Hatfield said the Crown would rely on evidence from Mr Crossman to "prove a number of tendencies on behalf of the accused to act in a particular way".
She had admitted hitting him in the head with a hammer when he was sleeping, after first saying the culprit was an intruder.
On another occasion she gave him a meal of tacos before setting the bedroom alight while her husband was asleep, the prosecutor said.
He was found to have sedatives in his system, despite not taking them knowingly.
Ms Manuel said in her police interviews her client denied any involvement in Mr Dunbar's death, knowing he intended to kill himself or was making plans to die.
But she told the jury people lie for different reasons, noting Darcy had previously admitted the offences involving her husband and believed police now regarded her as a murder suspect.
If she had helped him search suicide sites, went with him to buy the gas and hadn't alerted medical professionals, "don't you think she might feel she had something to hide?".
The trial continues before Justice Julia Lonergan.
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