It's possible William Tyrrell's foster mother created a "false memory" about seeing suspicious cars the day the young boy went missing, a memory expert has told an inquest.
Doubt was also cast over a witness's account about seeing the three-year-old boy standing unrestrained in the back of a four-wheel-drive being driven out of Kendall on the NSW mid-north coast in September 2014.
William hasn't been seen since disappearing from his foster grandmother's home in Kendall the morning of September 12, 2014.
Discussing the foster mother's account of seeing two cars parked in the street from where William went missing, forensic psychology academic Helen Paterson told the boy's inquest on Wednesday it was "possibly" a false memory.
Dr Paterson said information learned after an event had the potential to cloud or distort future retellings of the event.
A leading question may have been asked about suspicious vehicles and prompted the woman to search her memory for pictures, the University of Sydney academic said.
"It could be there was a true event ... she saw those cars in that location at a different time," Dr Paterson said.
"But then she mistakenly attributed it to the morning before William disappeared."
Two days after William went missing, the foster mother told police she recalled seeing one white and one grey car parked between two driveways the morning of his disappearance.
She later said the memory of the cars was "burnt into my brain".
"I'm unable to say if it's a true or false memory," Dr Paterson said.
The expert was also questioned over Kendall resident Ronald Chapman's account of seeing William dressed in a Spider-Man suit go by his home on September 12.
Mr Chapman told the inquest in March 2020 that he was "sure" the boy he saw in the back of a Toyota Landcruiser was William Tyrrell.
Dr Paterson said Mr Chapman's retelling of the memory changed over time, with an initial mention of a cape not appearing later and the later accounts told with more confidence and accuracy about key events.
The memory expert said it could be the case Mr Chapman was incorporating "post-event information" such as news reports in his memory reconstruction.
She said her evidence assumed Mr Chapman and the foster mother were giving accounts in good faith.
"There are ways that people can report information that is not true but they are not lying," Dr Paterson said.
The inquest also heard Detective Chief Inspector David Laidlaw, who replaced Gary Jubelin as supervisor of the William Tyrrell police investigation, never received a formal handover from his predecessor.
Det Chief Insp Laidlaw said that was because he'd found the discussion of the investigation "wasn't at the fore" of numerous chats Jubelin had with him in early 2019.
"In my view, I was going to get more knowledge from all those who worked on it, not just one person," he said.
Jubelin was sidelined after it emerged he'd illegally recorded a person of interest on four occasions in 2017 and 2018.
Coroner Harriet Grahame on Tuesday rejected a bid to have Jubelin, who quit the force in May 2019, give evidence at the inquest.
Det Chief Insp Laidlaw said a team of investigators were still working full time on the case, with officers to go back to the mid-north coast later this year.
"We never will (give up)," he said.
Australian Associated Press
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