A woman who murdered her partner for his estate showed a determined and ugly persistence in planning to carry out the killing and made "two dry runs" beforehand, a NSW court was told.
Natasha Beth Darcy left a false trail to create the impression that grazier Mathew Dunbar had died of suicide, her sentence hearing in the NSW Supreme Court was told on Friday.
She even screamed at paramedics to keep performing CPR after they declared him dead.
The 42-year-old died in his bed on his Pandora property in the Northern Tablelands town of Walcha on August 2, 2017.
But her "determined ugly persistence and planning" was shown in her obsessive internet searches on various methods of killing a person, whilst ensuring she inherited his estate, the court was told.
Justice Julia Lonergan noted there was a disturbing element to the idea of Darcy "watching videos how to complete the execution" opposite the man she lives with while having lunch.
A victim impact statement by Mr Dunbar's mother described how her kind-hearted son had hoped to turn Darcy's life around.
"Mathew knew she had troubles and hoped to change her," she said.
"He did not deserve this ... I miss him so much, he was so loving and caring, you would not find another being like him."
"Mathew was my only child and now I am on my own, I have lost my rock and my life won't be the same again."
The Crown submitted Darcy had exploited the entire relationship for her own financial gain and her murder plot had included "two dry runs".
In June 2017 Mr Dunbar was seen by police to be slurring his words, unsteady on his feet, with a very dry mouth and extremely pale, consistent with a drug overdose by Darcy, prosecutor Brett Hatfield said.
She also sent a fake text message from his phone to her's saying "I am sorry beautiful lady for everything I put you through you deserve better than this," he submitted.
Then in July after a series of internet searches on injecting muscles, and specifically the calf muscle, Mr Dunbar sustained a calf injury that potentially required surgery.
Subsequent mobile searches by Darcy included "what happens if you don't urinate in a coma," and "can't wee unconscious," Mr Hatfield said.
Defence lawyer Janet Manuell SC argued while these events were suspicious, they could not be proven beyond a reasonable doubt.
An expert report tendered to the court found Darcy had a complex personality structure with anxiety disorder.
Ms Manuell said she could potentially be seen to have an obsessive quality too, given the striking amount of murderous internet searches she made.
"It's very hard to explain why somebody would make so many searches, accepting, that Ms Darcy had settled on a particular course of action," she said.
Darcy's extensive mobile phone and computer research was read out during her trial.
Gas bottles, whether certain chemicals could stop the heart, murder by inducing a heart attack, poisonous mushrooms, and an article headlined "science of getting away with murder" were just some later found to have been erased.
"Can police see past web search history," was also looked up.
The couple met on a dating website in 2014, but the Crown argues it didn't take long for Darcy to start pushing for Mr Dunbar to change his will so she would inherit his $3.5 million property.
Darcy is due to be sentenced on December 3.
