Accused triple-murderer Erin Patterson has rejected a prosecution claim she carried out factory resets in a bid to deceive police about her mobile phones, as she came to the end of eight days in the witness box in her Supreme Court trial.

Ms Patterson has been charged with three counts of murder and one count of attempted murder after three relatives — her parents-in-law Don and Gail Patterson, and Gail’s sister Heather Wilkinson — died from death cap mushroom poisoning following a lunch at her house on July 29, 2023.

A fourth lunch guest, Heather’s husband Ian Wilkinson, became gravely ill after the meal but survived.

At the close of the prosecution’s cross-examination, Ms Patterson reiterated her innocence of all four charges.

In rapid fire, crown prosecutor Nanette Rogers SC put to Ms Patterson the crux of the charges: that she “deliberately sourced death cap mushrooms” and put them in the dish she served to her lunch guests “intending to kill them”.

“Agree or disagree?” Dr Rogers asked.

“Disagree,” Ms Patterson responded.

The trial has now concluded hearing evidence and will move to closing arguments from the prosecution and defence, before the judge issues final instructions to the jury ahead of their deliberation.

Prosecution accuse Ms Patterson of hiding mobile phone from police

Over the course of the past six weeks of the murder trial, the prosecution has alleged Ms Patterson owned and used two phones with two separate SIM cards — Phone A and Phone B.

Phone A was never recovered by police, but under cross-examination on Thursday Ms Patterson rejected prosecutors’ assertion that that was because she had hidden the phone from police.

Dr Rogers showed the court extensive phone records from a SIM card that was in Phone A up until August 5, 2023, a week after the lunch.

The records indicated the phone was in regular use up until sometime between 12:01pm and 1:45pm, when the SIM card in Phone A lost connection with the network.

At that time, police were conducting a search of Ms Patterson’s Leongatha home.

Dr Rogers put to Ms Patterson that she removed the SIM card from Phone A when she was “afforded privacy to speak with a lawyer while police were at your home”.

Ms Patterson disagreed and said her calls to a lawyer occurred at 2pm, after the alleged loss of connection.

Ms Patterson rejects prosecution explanation for factory resets

Ms Patterson also rejected a claim from prosecutors that the reason she had conducted three factory resets on Phone B was so she could deceive police and “pass [it] off” as her regular phone.

When police executed a search warrant on Ms Patterson’s home on August 5, a week after the deadly lunch, it was Phone B that she gave to police. 

The prosecution suggested she did so as she knew there was no data on the phone to potentially incriminate her, which Ms Patterson denied.

Dr Rogers took Ms Patterson to records of three factory resets made on Phone B.

Ms Patterson had previously told the court of the following reasons for factory resetting the phone on these dates in 2023:

• August 2: Ms Patterson said her son had taken this phone on a school camp and had dropped it in mud, requiring it to be cleaned. She said she had figured out it was capable of being used on August 2. “So I put it on charge and at some point factory reset it,” Ms Patterson told the court.
• August 5: Ms Patterson said this reset was carried out to remove images she thought would make her look guilty. “I knew that there were photos in there of mushrooms and the dehydrator and I just panicked and didn’t want them [the detectives searching the house] to see them,” she told the court.
• August 6: Ms Patterson said she carried out this factory reset because “at some point, after the search of my house and the interview and the detectives had brought me home, I remember thinking ‘I wonder if I can log into my Google account and see where all my devices are. So I did that, and I could see my phone, and [my children’s devices], and it was really stupid, but I thought, ‘I wonder if they’ve been silly enough to leave it connected to the internet’, so I hit factory reset to see what happened and it did”.

On Thursday, Dr Rogers suggested to Ms Patterson she had carried out those resets for another reason.

“I suggest that you did three factory resets of this phone, Phone B … to conceal the true contents of Phone B … so you could then pass off Phone B as your usual mobile phone, without police realising,” Dr Rogers says.

Ms Patterson agreed she carried out the three resets, but disagreed that she did for the reasons Dr Rogers suggested.

Dr Rogers went on to assert that it was “all about hiding the contents of your usual mobile phone, Phone A”, which she asserted Ms Patterson had “deliberately concealed” because she knew the data on that device would “incriminate” her.

Ms Patterson rejected this assertion too.

Emotional close to Ms Patterson’s evidence

Throughout several days of cross-examination, Ms Patterson’s voice largely remained level as she answered prosecutors’ questions.

But during re-examination by her barrister, Colin Mandy SC, her voice became choked when asked about the need for her to pack her daughter’s bag for a ballet rehearsal on the Monday after the lunch.

The prosecution asserted this was in fact never required, but Ms Patterson reaffirmed under re-examination that it was.

Ms Patterson’s voice again cracked when discussing her son’s flying lesson, explaining she did not cancel it following the lunch as he was “really passionate” about flying and “I just didn’t want to disappoint him”.

The defence also asked about contradictions that arose during Ms Patterson’s cross-examination, such as her claim she had had an appointment in September 2023 to explore gastric-bypass surgery at a Melbourne clinic that did not in fact offer it.

Ms Patterson told the court that in 2023, she had believed the clinic offered gastric-band surgery, but on Thursday said she was “obviously mistaken”. She told the court she had also intended to explore liposuction options.

Mr Mandy then asked Ms Patterson about the sixth beef Wellington she cooked, which the prosecution has alleged was prepared in case her estranged husband attended the lunch and she could poison him as well.

Ms Patterson told the court she simply had an extra steak because of the way the eye fillets she bought were packaged.

“I had five twin packs, I put two of the twin packs in the freezer and just decided to use the other six, I had enough ingredients … so I did that,” she said.

The trial continues.