Officers were questioning her about the "suspicious circumstances" surrounding Mathew Dunbar's death.

One was a Google search made early on the day he died, questioning if the type of gas used would "show up in an autopsy".

The only thing Natasha Beth Darcy could think of is that "he didn't want to get me in trouble," she said in her police interview played to a NSW Supreme Court jury on Thursday.

"Why would he care?" A police officer responds, before asking if this was his concern, "Why he wouldn't write a note or something to explain?"

"I keep asking myself the same thing, why didn't he write a note or anything, I have no idea," Darcy said.

The 46-year-old has pleaded not guilty 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. Her guilty plea to aiding or abetting suicide was rejected by the Crown.

Darcy said she phoned emergency services when she found him, before administering CPR saying she was hopeful because he felt warm.

But then she noticed the gas cylinder bottle and other paraphernalia.

"I suppose I'd realised ... he'd tried to kill himself. I worked that out from an early point."

Why she never noticed the heavy bottle being brought into the bedroom was questioned, along with its weight given Mr Dunbar had an infected leg and often needed crutches to walk.

Family members who were present also dispute her story that she did not cook dinner that evening.

The Crown argues Darcy sedated and gassed Mr Dunbar in a bid to inherit his $3.5 million property after his will was changed to include her.

In her interview with police Darcy said she had nothing to do with organising the gas cylinder bottle the couple picked up together.

Police asked why then did the woman at the store tell them a female ordered it and said Matt Dunbar would be collecting it in his car for an event.

"That was not me," she said.

In 2015 Mr Dunbar changed his will leaving all of the estate to Darcy, but she was only made aware of this a day before her interview with police, she says.

Once Darcy was told she was the main beneficiary she repeated "I don't think that's correct," adding she didn't want to be as people would "say things they've been saying".

During their investigation of the bedroom detectives found anti-psychotic medication Darcy denies using but says a friend gave her to help sleep.

After they tell her the box was found ripped open she declines to give her friend's details.

"Do I have to give you her name? ... she's not a dealer or anything."

Darcy maintains Mr Dunbar was afflicted by physical and mental health issues that deteriorated after the death of his friend, which also stirred up questions about his sexuality.

"Craig was openly gay but Matt tried to hide it," she said.

"I would say we had a normal marriage-type relationship without the sex."

When asked point blank if she had anything to do with her partner's death she repeats through tears, "No" and "most certainly not".

The trial continues.

Australian Associated Press