Blackburn (18) denies that, on April 25, at Fraser Place and Newton Avenue, Arbroath, he assaulted Miss McCagh by throwing petrol over her, a bed, and setting fire to her whereby she was so injured she died in hospital, and he murdered her.

Mr Murray put it to the witness that Stewart Blackburn had told lies during the three interviews the detectives conducted over the course of the weekend following Jessica McCagh’s death.

DC Simpson agreed.

Mr Murray said there were also truths, and gave as an example the accused’s account of trying to douse the flames on his burning girlfriend.

Counsel referred to the accused saying he grabbed pots, cups and looked for wet towels to pour water over her.

He referred the officer to a photograph of the hallway at 83 Bloomfield Road, in Arbroath, taken on April 25, after the fire was extinguished.

The officer agreed a pot on the right hand side and cup on the left hand side could be seen inside the hall, in a shot taken from the doorway of the flat. Counsel then contrasted the account given by upstairs neighbour Ricci Foreman of the accused running past him as soon as he got in the door.

Mr Murray said the witness recounted Jessica in flames collapsing against the doorway.

The accused in one of his statements to police also described Jessica collapsing against the doorway.

Mr Murray put it to DC Simpson that if Mr Foreman’s description of the accused running out was correct he could not have known this unless someone had told him. He said another mystery was that no one knew who the officer was, who, “while there was still smoke rolling from that flat, asked Blackburn, did you pour petrol over her.”

DC Simpson said he did not know who the officer was and it was not a question he, as an experienced detective, would have asked in those circumstances.

Mr Murray asked DC Simpson if he was aware of the statement given by Ricci Foreman at the time he was interviewing the accused. The officer agreed he had seen the statement.

Counsel referred him to a section in which “the accused, in a distressed state, in the ambulance in conversation with Ricci Foreman, said, ‘They are saying I poured petrol on her.’

“Possibly he said that because of the question you, as an experienced officer, would never have asked in your life.”

DC Simpson replied, “Correct.”

‘EXTREMELY HIGH LEVEL OF PETROL’

Higher levels of petrol were obtained from the evidence bag containing Jessica’s burnt clothing than would be found from the inside of a petrol can, a specialist fire forensic scientist then told the court.

Rebecca Peplar (34), who began her career with Tayside Police and now works as manager of a forensic scientist company in Reading, said she was asked to carry out an analysis of clothing taken from both Blackburn and Jessica. She tested for the presence of accelerants and to identify any accelerants found.

From the accused’s tracksuit bottoms, a probe recorded 13 parts per million from the evidence bag and there was “moderate scientific support” for the presence of low levels of petrol.

A bag containing boxer shorts gave a reading of 4.6 parts per million and a t-shirt 2.7 parts per million with no positive test for petrol. The bag containing Jessica’s burnt clothes gave a reading of 2020 parts per million, with “conclusive scientific support for the presence of petrol”.

She told the court, “This is an extremely high level.

“In my experience I have rarely ever come across such a level of petrol from burnt clothing. It is usually found in the interior of petrol cans. In fact higher.”

She told the court, “I analysed a petrol can for a different case last week and that only had a reading of 1400 parts per million.

“I have rarely observed such a high level of volatiles on an item of burnt clothing.”

The only case she could recall gave a reading of 600 to 700 parts per million on a cap when someone had petrol poured over their head and set it alight.

The trial continues.

YESTERDAY’S LATE EVIDENCE

Towards the end of three hours of police interviews, spread over two days, Blckburn confessed he had thrown a plastic jerry can containing petrol at Jessica during an argument and it spilled fuel over her.

He continued to insist he had not deliberately set her alight, repeatedly telling the detectives interviewing him, “I am not that sick.”

Detective Constable Gary Simpson, who led questioning during the interviews shown to the jury at the High Court in Livingston, confronted Blackburn with the fact that, while he had been relatively uninjured, his girlfriend had been covered in flames “from head to toe”.

Shortly before the admission he was asked, “Why is she covered in burns and you are not? Why is she smelling of petrol? Help me fill in those blanks.”

He answered, “I have never seen a fire go up so quick. I have never seen anyone go on fire before, I have never seen anyone burning.”

Telling the officers he had never seen anyone die, he said, “You don’t know how hard it is to go through all this.”

Pressed again to explain how 17-year-old Jessica was fatally injured and he was not, he said, “I’ll tell you the truth, I am going to jail for this anyway, right? I threw the jerry can over her when we first came in the house. As she went to bed, I threw the jerry can at her.”

DC Simpson asked, “Was the jerry can open? Did she get covered in petrol?” To both questions, the accused answered, “Yeah.”

After the incident he claimed he was trying to speak to her “nicely”.

He paused and continued, “I know I am going to get done for it anyway, so there’s no point in lying any more.

“I came in and my jerry can of fuel is sitting on the bed. Jessica jamp (jumped) on the bed. The petrol can did fall over. I am not saying that is how I caused the fire, it did fall over.”

He said Jessica had been “moaning” about the petrol can being in the bedroom and he threw it “just to annoy her”.

Blackburn then said, “I didn’t want this to happen, you know I didn’t.”

When he threw the petrol, he said, Jessica shouted at him. He went to the living room to roll a cannabis cigarette and when he returned to the bedroom, she was on the bed.

“I was like, ‘Jessica, you OK’, and she’s like ‘Yeah’ in her wee voice.”

He said he asked her if she wanted some of the cannabis cigarette and she sat up on the bed.

During the interviews the accused repeatedly told the detectives that when he lit the joint, pieces or “little bombs” fell from the end and the fire started.

After his admission, he asked the officers, “Am I going to court tomorrow?” He also asked if he would be going to jail. He was told that would be a decision for the fiscal.

Blackburn then said, “Cause, I just, if I go to jail, I can’t even go to her funeral or nothing.”

DC Simpson responded, “That’s something we’ll deal with at a later date.”

Blackburn said, “I can’t, ’cause I’ll lose everything in the house.”

Told the officers would return to speak to him about the charges he would face later, he said, “For murder?” He added, “That’s my life gone in jail.”

Early in the interview, detectives challenged Blackburn about his earlier accounts of events on the night of April 24-25, leading up to the fatal fire in the early hours of that morning.

He was asked to explain why witnesses contradicted his version of events. He continued to deny he had been punched by Jessica at a party.

He denied he had hit Jessica on the way home but conceded he had been pushing her. Men who shouted at him had followed them and he admitted that when they reached his flat in Bloomfield Road he went back out with his dogs and an air rifle, and discharged it at them to make them leave.

He said he was annoyed with the men and also annoyed at Jessica when he got back in and had punched a mirror, breaking it, and Jessica had slammed the bedroom door and shouted at him.

He suggested this was the sounds of a row neighbours had heard.

At that stage of the interview he continued to deny he had poured petrol over her and set her on fire and denied he had been telling lies.

He said, “I want to be able to see Jessica one last time.” He said he wanted to be able to leave Arbroath and go and see his mother.

In an emotional exchange, he said, “I tried to kill myself earlier on. Just to be with her (Jessica).

“She had a better life than me. She was working, she had a nice happy family. What have I got? Just me. I love Jessica to pieces. I could never do anything like that.”