A TEENAGER who murdered her grandfather fabricated an eleventh-hour lie to tarnish the name of her victim and excuse her crime, a court has heard.

Brittney Jade Dwyer, 19, from the Gold Coast, faced sentencing submissions on Monday after admitting to murdering her grandfather, Robert Whitwell, 81, in his unit at Craigmore in Adelaide’s northern suburbs in August last year.

Supreme Court Justice Kevin Nicholson heard Dwyer told a psychiatrist that her grandfather may have sexually molested her as a child — but she wasn’t sure if it was real or not.

“It is a most unpleasant assertion. It’s unfounded in any other material,” prosecutor Jim Pearce told the court.

He said “at one minute to midnight” Dwyer was having flashbacks about something her victim may or may not have done, despite never having raised this as a motive at any other point in the investigation.

“In my submission, the court would be entitled to infer, with the absence of evidence from Ms Dwyer about this, that it is just simply an invention designed to give her an explanation for why she acted as she did,” he said.

“Because the only other explanation is a premeditated, pre-planned, almost sociopathic killing.

“It’s insidious to a man who was murdered in that way.”

Mr Pearce said “the prisoner ... just leaves it hanging and that man is not here to defend himself”.

“In those extensive records of interview where Ms Dwyer was putting her cards on the table to police, where she put forward her version of events, which developed over time.

“It started out with her saying, ‘no I wasn’t involved’ to eventually the second interview saying, ‘yes I was there, I did it, I was the perpetrator’.

“Then in the fifth interview, she was pressed further about her underlying motives.

“In all of the interviews, there was not one syllable uttered by her on any occasion that her grandfather had done anything to her.

“Or that she had gone there, as she tells (the psychiatrist), to speak to her grandfather about these issues.”

He asked Justice Nicholson to place no weight on that part of the psychiatric report.

Dwyer’s lawyer, Craig Caldicott, said his client wasn’t sure whether “her flashbacks” were real or not and it would not be presented as a motive in the killing.

He said the motivation was to steal money from her grandfather.

Her case was then adjourned until after her co-accused, Bernadette Burns, has been tried for her alleged role in the killing.

ACCOMPLICE GIVEN SUSPENDED SENTENCE

Another friend, Shelby Lee Angie Holmes, 19, was sentenced on Monday afternoon for trespassing on Mr Whitwell’s property in the months leading up to the murder.

Holmes was jailed for 17 months with a non-parole period of nine months, suspended on the condition she be of good behaviour for three years.

The court was told Dwyer and Holmes drove from Queensland to Adelaide to rob Mr Whitwell of “thousands of dollars” of the “hundreds of thousands” which they believed was kept in his shed.

But the girls were frightened off by a sensor light, barking dogs and a nearby neighbour.

Last month, Mr Whitwell’s brothers told how they embraced his crying granddaughter in the days after his death — only to discover they had been comforting his killer.

Dwyer had to listen as her family outlined their devastation and despair in victim impact statements read out in the Supreme Court by prosecutor Jim Pearce.

In his statement, Mr Whitwell’s brother Geoffrey Whitwell said he was devastated by his brother’s murder and missed him dearly.

“Bob and I were very close,” he wrote.

“We always came together for Christmas and Bob’s birthday was special because it was on the same day as my wife’s (birthday).”

He wrote that he would speak with his older brother on the phone frequently.

“But I’ll never hear the phone ring with my brother on the other end,” he said in his statement.

Mr Whitwell said Dwyer, her mother Tonya Dwyer and brother all flew to Adelaide from Queensland after the murder.

“We welcomed you into our home, embraced you and comforted you, all the while you wept with your fake tears and made comments like ‘my poor poppa’,” he said.

“I now know that I had been embracing and comforting my brother’s killer. You are a master of deception, I will give you that.

“I will never forgive you. You’re a cruel, deceitful person with no regard for human life — I believe you are dangerous and evil and deserve the highest penalty.”

Mr Whitwell’s other brother, Peter Whitwell, also spoke of inviting Dwyer into the family home and comforting her in the days after his death.

“We were just coming to terms with his death when we found out it was his own granddaughter who was responsible,” he said in his statement.

Tonya Dwyer — whose daughter killed her father — also provided a statement to the court, saying she had been a happy wife, mother and daughter until everything changed on May 2 last year.

“(Now) I feel like I’m drowning in life,” she said.

Dwyer’s father, Garry Dwyer, described his former father-in-law as a “great man, who loved his family”.

He asked the court to impose an “appropriate” jail term on his daughter.

Dwyer pleaded guilty to the murder and in February admitted to a further charge of aggravated serious criminal trespass between April 30 last year and May 2.