An inquest coroner concluded the death of Mary Gregory was accidental after he received a report from Jim Stone which stated the fire took hold when she dropped or attempted to dispose of a cigarette in the front bedroom of her bungalow in Lancashire in the early hours of May 28, 2018.
Lancashire Fire and Rescue Service incident intelligence officer Mr Stone ruled out in his August 2018 report the possibility the blaze in Heysham was started deliberately and said there was no evidence of third party involvement.
However, he was asked by police to review the matter following an alleged confession in May 2019 by Tiernan Darnton, 21, in a counselling session in which he was said to have admitted to setting fire to curtains in the property with a lighter.
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An examination of his mobile phone and laptop revealed a number of Google searches after the blaze including “I want to cause evil”, “I’m a murderer”, “I’m a monster and I’m going to hell” and “urge to kill again”.
Preston Crown Court has also heard that weeks after Mrs Gregory’s funeral at Lancaster and Morecambe Crematorium the defendant told two friends during a game of Truth or Dare that he had killed Mrs Gregory, although they thought he was joking.
Darnton went on to tell police the Truth or Dare comments were not true and he was trying to impress his “edgy” friends. He added he had not deliberately or accidentally started the fire at the address in Levens Drive.
The jury heard Mr Stone’s view on the cause of the fire remained unchanged and a deliberate ignition of curtains in the bedroom with a naked flame was not consistent with what he saw when he visited the scene in May 2018.
Giving evidence on Thursday, he said: “I still feel a cigarette was the most likely cause of the fire.”
He agreed with prosecutor David McLachlan QC that no cigarette butt or unsmoked cigarettes were found in the property.
Mr McLachlan asked: “Could a deliberate ignition be a realistic possibility in this case?”
Mr Stone replied: “I consider it’s highly unlikely.”
The investigator agreed, though, that he now could not “totally” discount that a deliberate act took place.
A fire examination expert for the prosecution, forensic scientist Graham Stuart Baxter, has said the chance a dropped or discarded cigarette starting the blaze was “extremely remote”.
The court was told Mr Baxter reviewed the case from photographic images and did not attend the scene of the fire.
The jury has also heard statements from a number of carers who regularly visited Mrs Gregory, who had dementia, and said they had never seen her smoke in the front bedroom.
Mrs Gregory was treated in hospital for smoke inhalation and died at the Royal Lancaster Infirmary on June 1 2018.
Darnton denies murder.
The trial continues on Friday.