Jessica McCagh died of her injuries at Ninewells Hospital
A teenager who suffered 85% burns after a fire in the bedroom of an Arbroath flat may have been prevented from escaping, a murder trial has heard.
Forensic expert Andrew Wade told the High Court in Livingston there was evidence the bedroom door had been held shut during the blaze.
Jessica McCagh, 17, died on 25 April after the fire at the home she shared with boyfriend Stewart Blackburn, 18.
He denies murder by dousing her in petrol and lighting it.
Mr Wade, 54, said his scientific findings were "consistent" with the door having been held shut by the accused.
The court heard he had examined more than 1,000 fires in his career, including the Bloomfield Road fire which killed Miss McCagh.
Mr Wade said damage found on the handle of the bedroom door was "indicative of mechanical force being applied", for example by the door being pulled from one side. Reading from the conclusions of his report into the fire, he told the eighth day of the trial: "The bedroom door had been closed for the duration of the fire and Jessica McCagh was unable to escape through it."
He also said that the "severe destruction" of one corner of the bed and the damage in that area was "consistent with ignition of flammable liquid, such as petrol".
He said: "In our view, the fire was the result of ignition of petrol on the clothing of Jessica McCagh and the bed she was sitting on and this petrol was ignited by a naked flame, such as from a match, cigarette lighter or a lit taper."
Burns to Mr Blackburn's clothing around the legs were consistent with him having been in the area during the fire, he added.
Solicitor General Frank Mulholland QC, prosecuting, then put a scenario to the witness.
'Did throw petrol'
"Jessica McCagh is sitting in the corner of the bed. Petrol is poured on her. She is set on fire with the naked flame from a lighter. The fire takes effect.
"Mr Blackburn then leaves the room, the door is closed and he holds it closed.
"Is that scenario consistent with your findings?"
Mr Wade replied: "Yes it is."
Following the testimony, jurors were read a transcript from a judicial examination held in Arbroath before Sheriff Kevin Veal on 6 May.
During the private hearing, Mr Blackburn told the sheriff: "I did throw petrol at her but not intentionally straight over her."
He added: "I didn't mean it, to throw the petrol at her."
Mr Blackburn said there had been an argument and he "fell out" with Miss McCagh.
"The petrol, when it caught on fire it was an accident," he said.
The judge, Lord Bracadale, adjourned the case until Tuesday.