Man accused of murder blames victim's ex-wife in Adelaide court

A man accused of murdering a woman in Adelaide's southern suburbs has told a court he is not to blame for her death, and instead alleged the crime was committed by the victim's ex-wife.

Johnathan Paul Parker, 51, is standing trial in South Australia's Supreme Court after pleading not guilty to murdering 38-year-old Krystal Marshall at her Aldinga Beach home in October 2023.

However, at the start of the trial, he pleaded guilty to destroying her remains by setting them on fire.

On Monday, Parker took the stand in his defence and told the court that Anastasia Marshall — Krystal Marshall's ex-wife — was responsible for her death.

He said he had attempted to cover up the crime because he was in an "intimate" relationship with Anastasia Marshall and he "was in love with her".

The court previously heard that Parker, Krystal Marshall and Anastasia Marshall were all living at the same house.

Parker told the court that on October 19, 2023, the trio had an argument before Krystal Marshall's alleged murder.

"I went out and had a couple of cones just to chill out … just to remove myself from the situation," he said.

He added that it "wouldn't have been 10 minutes" before he walked back into the home and asked Anastasia Marshall if the two had stopped arguing.

"I opened up the door and I seen [sic] Krystal's body face down on the bed.

"I don't remember exactly how her arms were. But all I remember is seeing her face was down on the bed."

The 51-year-old also told the court that his "mind went to mush" after he confronted Anastasia Marshall.

"I walked back into Anastasia's room and said, 'What the f*** have you done?," Parker told the court.

"She looked at me and said, 'What does it matter? She's dead'."

Parker also told the court that he was not sure why he "thought to use fire" a day later — on October 20 — but that he was "trying to disguise what had happened".

"I just soaked a heap of wood in accelerant," he said.

"I put that over Krystal's body, then I used the last of the accelerant and tipped it over the bed.

"I can't remember how I lit the fire … I know there were some candles in the hallway."

When asked by his barrister Bill Boucaut KC, Parker said his motivation to set Krystal Marshall's body on fire was to protect Anastasia Marshall.

"I thought that she loved me."

He added that Krystal Marshall and Anastasia Marshall had a "tumultuous relationship" and "they argued a lot".

"It was common knowledge that they didn't get along that well," Parker told the court.

"They went from just yelling to bumping chests."

Prosecutor asks if evidence 'made up'

In cross examination, prosecutor Jim Pearce KC asked Parker how he knew that Anastasia Marshall had allegedly killed Krystal Marshall if he had not explicitly been told.

Parker told the court that it was the "way she looked at me".

Mr Pearce then asked: "Was there something evil in the way she looked at you?"

"Yeah," Parker responded.

"On what you're telling us, you had no idea how Krystal had died, did you?," Mr Pearce then asked.

Parker responded: "That's correct."

Mr Pearce asked if Parker's evidence about how he knew Krystal Marshall was dead was "made up", but Parker said it was "all true".

He also asked the alleged murderer why he did not check for a pulse or call an ambulance, and questioned whether it had crossed his mind that she could have died from natural causes.

"The reason that you didn't make any inquiries is because you didn't have to because you are the one that killed her. You knew full well that she was dead, and how she died, because you were responsible," Mr Pearce said.

"That's not correct," Parker responded.

The trial was previously played prison telephone intercepts in which Anastasia Marshall can be heard telling Parker that he had "f***ing murdered my wife for no f***ing reason".

Mr Pearce will continue his cross-examination of Parker on Tuesday.

The trial is expected to conclude next week.