A student who admitted killing his step-grandmother in a game of truth or dare researched his “urge to kill again” online, a court has heard, as he was convicted of her murder.

       Tiernan Darnton, 21, was found guilty of killing 94-year-old Mary Gregory, who was discovered under a table in her bungalow in Heysham, Lancashire, in May 2018 and died four days later.

       A 2018 inquest had initially ruled that she was the victim of an accidental house fire after an investigation by Lancashire Fire and Rescue Service concluded the most probable cause was a carelessly discarded cigarette and ruled out any third-party involvement. A coroner recorded a verdict of an accidental death.

       However, police reopened the case in May 2019 following comments made by Darnton during a counselling session in which he confessed to killing Mrs Gregory, his stepfather’s mother, by using a lighter to set a curtain on fire.

       During his trial at Preston Crown Court, the prosecution said that attempts were made to hamper any escape by Mrs Gregory, with a table placed in front of the conservatory doors, the unplugging of a phone cable and the dismantling of a smoke alarm.

       The jury were also shown drawings found at Darnton’s home address, outlining the floor plan of Mrs Gregory’s bungalow, which contained labels including “good hiding place” and “quick exit”, as well as references to needing a “good alibi”.

       When police first opened their investigation into Darnton, it emerged that he had also confessed his “darkest secret” to friends during a game of truth or dare several weeks after Mrs Gregory’s death.

       He told the pair: “I have a secret I haven’t told anyone. I may have killed someone.”

       When pressed, Darnton said he started the blaze because he did not want Mrs Gregory, formerly from Nuneaton, Warwickshire, to suffer any longer from dementia, the court heard.

       Darnton’s friends did not believe him and he persuaded them to keep quiet, but he told a counsellor in May 2019 about a friend “who could send me to prison cos of what he knows”.

       The female counsellor ended the session by saying to him: “I’m not really clear what you’re saying but I think you’re trying to tell me you’ve killed someone,” to which Darnton mouthed: “Yes.”

       A week later, he told the counsellor and his stepfather, Chris Gregory, 66, that he had started the fire and the matter was later passed to the police by the counsellor, the court was told.

       Darnton, a former student at Kendal College and Lancaster & Morecambe College, was arrested at his family home in Combermere Road, Heysham, in May 2019.

       Examination of his mobile phone and laptop found internet searches made after the fire including “I’m a murderer”, “I’m a monster and I’m going to hell”, “I want to cause evil” and “Urge to kill again”.

       Giving evidence at his trial, Darnton said the case was “all a big misunderstanding” and his confessions were false and that he only wanted to impress his “edgy” friends in the truth or dare game.

       Darnton said his comments to the counsellor that he had killed somebody were “attention-seeking”, but denied saying he had set his step-grandmother’s house alight.

       An investigator from the Lancashire Fire Service ruled in August 2018 that the probable cause of the fire at Mrs Gregory’s home was a cigarette and told the jury his opinion was unchanged.

       However, a fire examination expert for the prosecution said the chances of that were “extremely remote” and he believed the blaze was most likely started by naked flame ignition near the front bedroom window of the property.

       Mr Gregory, giving evidence for the defence, said Darnton, whom he home-schooled, had been suffering from depression for a number of years and was “plagued by intrusive thoughts which were very, very disturbing”.

       Sentencing will take place on Friday.