IN THE hour and a half between the time Erin Patterson discharged herself from the Leongatha Hospital, against medical advice at 8.10am on Monday, July 31, 2023, and returned at 9.48am, there is a 28-minute gap in her phone records.
It was one of the issues probed at Mrs Patterson’s murder trial in Morwell on Monday and Tuesday this week when Dr Matthew Sorrell, a highly qualified computer science engineer and a veteran of more than 400 criminal cases Australia-wide was in the witness stand.
Under cross-examination by Colin Mandy SC for the defence, after two days of mobile phone data testimony, Dr Sorrell agreed with Mr Mandy’s proposition that “we would be speculating as to what happened in that intervening period?”
But it didn’t stop Dr Sorrell providing his expert opinion on which movements of the accused's mobile phone handset, between 8am and 10am, on July 31, 2023, were “most consistent” with the phone records he had been asked by police to analyse.
Prosecutor Jane Warren drew Dr Sorrell’s attention to a particular set of mobile phone records including a connection with a Leongatha phone tower at 8.52am, a connection with Koonwarra at 8.54am and then a connection with Outtrim at 8.55am on July 31, 2023, before a break in transmission until reconnecting with the Leongatha tower again at 9.23am. She asked him what he could say about the location of Erin Patterson’s mobile phone that morning.
He said there were a number of possible explanations but that the records were most consistent with the handset moving away from Leongatha at 8.52am, down the main road south-west of Leongatha.
“I'm sorry, I don't know the name of the major road, it's south-west of Leongatha, and would take the phone into the dominant area of the Koonwarra tower. I don't believe the phone is headed towards Koonwarra itself, because Outtrim now drags that coverage interpretation westward,” said Dr Sorrell.
He said the data demonstrated a trend that the phone was moving to the west, towards the Outtrim postcode, creating the possibility of a visit into that area but that it wasn’t strongly supported by the evidence because of the 28-minute gap in the phone records.
During cross-examination, Mr Mandy asked Dr Sorrell about a range of factors that could change which communication tower offered service without much movement in the handset.
“So, the base station that gives you the best service at the front door of your house might be different to the base station that gives you the best service at the back door?” asked Mr Mandy.
Dr Sorrell agreed.
Dr Sorrell had been provided with just over four and a half years’ worth of phone records by police for analysis for Erin Patterson’s mobile phone ending in the number 783, homing in on three broad topics; records of any connections to the Outtrim area and connections to Loch area, especially evidence of spending time in those areas and also the discrete period of time between 8am and 10am on Monday, July 31, 2023.
Among the dates and times that emerged where the phone was likely to be stationary was May 22, 2023 at Outtrim between 11:24 and 11:49.
Asked by Ms Warren if the data was consistent or inconsistent with a possible visit to Nielson Street, Outtrim, Dr Sorrell said it was possible that there was a visit to Nielson Street at that time.
Two dates relating to Loch were also raised with Dr Sorrell by Ms Warren, one was April 28, 2023, the other was also May 22, 2023.
While Dr Sorrell acknowledged there was the potential for a visit to the Loch area between 9:14am and 10am on April 28, the absence of records didn’t definitively point to the phone being in and remaining in and around the Loch township during that period.
With regard to May 22, Dr Sorrell said the data was more consistent with the phone remaining relatively stationary in or around Loch between 9.24am and 10am that day.
In the 16-month period of an extract of Dr Sorrell’s mobile phone data analysis, between January 1, 2022 and May 22, 2023, Dr Sorrell identified 57 connections to relevant towers of which eight could be designated as possible visits to Loch or Outtrim.
In April 2023, Christine McKenzie, a retired pharmacist, photographed and documented death cap mushrooms growing at the Loch Recreation Reserve on the citizen scientist website iNaturalist, while on May 21, 2023, Royal Botanic Gardens’ mycologist Dr Tom May submitted photos and details of death cap mushrooms growing in Nielsen Street in Outtrim to the same website.
In court on Wednesday, May 21, 2025, a senior digital forensics officer at the cybercrime department, Shamen Fox-Henry revealed details obtained from Erin Patterson’s computer which indicated she had accessed the iNaturalist website in May 2022.
The triple murder trial, where Ms Patterson is accused of the murders of three of her in-laws and the attempted murder of another, arising out of a lunch of poisonous mushrooms in July 2023 continues in the Supreme Court in Morwell. It is expected to run for another week or two.
Erin Patterson has pleaded not guilty to all charges claiming that what happened at the family lunch prepared by her was a tragedy and a terrible accident
