Following minutes of speaking in tongues, Raelene Polymiadis also revealed she was terrified after committing a "mortal sin", her trial was told.
The recording was played on Tuesday at the South Australian Supreme Court trial for the 65-year-old, who has pleaded not guilty to murdering her parents with insulin.
Brenda and Lynton Anderson died in March 2022 and May 2023, respectively - both at the age of 94.
The recording, from a listening device in Polymiadis's car three days after she met with police in June 2023, was the second alleged confession played to the jury.
After four minutes of "speaking in tongues", a phenomenon prosecutor Michael Foundas said was known as glossolalia, Polymiadis repeatedly says: "Please, Lord, forgive my sin".
"What I did was a mortal sin … I am terrified and I am frightened and I am so worried for my children," she said.
"I didn't do it for any reason other than to try and put my mum and dad out of pain, Lord.
"That was ultimately ... what it was about, Lord. Ultimately, I wanted my parents to not have to go through the pain of things."
That followed an earlier recording from Polymiadis's car as she drove to an interview with Major Crime detectives on June 20, 2023.
In that recording, she said: "I have sinned twice in my life, and I hate it, but I also know ... your blessing, Lord, that they did not want to go to a nursing home, that was their wish."
During the subsequent three-and-a-half-hour interview, played to the court, Detective Brevet Sergeant John Olive told Polymiadis he suspected she had knowledge of the circumstances of her parents' deaths.
"If I'm being accused of something, it sounds really scary," she says.
Later, she insisted: "I have not administered insulin to them."
Notes found in Polymiadis's car show "what she told police in that interview was planned and curated," prosecutor Michael Foundas has told the jury.
"Ms Polymiadis has written to herself 'sob here', and that corresponds with a point in the interview where (she) commences sobbing," he said.
The court has heard Polymiadis, a type-1 diabetic with access to insulin, had been the last family member to see each parent before they became unwell.
Defence counsel Marie Shaw KC has told jurors that context and interpretation were issues with the alleged confessions.
She will begin cross-examination of Sergeant Olive on Thursday.
Mrs Anderson died from an insulin overdose after being taken to the Flinders Medical Centre.
Mr Anderson also died there after he was found unconscious on his kitchen floor with a large amount of insulin in his body.
The trial continues.
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