By Brian Smith

AN ARBROATH teenager who suffered fatal injuries was possibly prevented from escaping a blazing bedroom, a forensic fire investigator told a murder trial at the High Court in Livingston yesterday.

Rebecca Peplar, who began her career with Tayside Police and now works as manager of a forensic science company in Reading, said the pattern of the fire inside the bedroom and analysis of the damage to the door suggested it had not been opened until late in the course of the blaze.

Stewart Blackburn (18) denies that on April 25 at Fraser Place and Newton Avenue, Arbroath, he assaulted Jessica McCagh by seizing her, pulling her, slapping and punching her on the head, knocking her down and pushing her.

He further denies that in Newton Avenue he conducted himself in a disorderly manner, pointed an air rifle at two men, repeatedly pulled the trigger, placing them in a state of fear and alarm, and committed a breach of the peace.

He also denies that at the flat he and Miss McCagh shared in Bloomfield Road he possessed cannabis resin.

He denies that at their home he assaulted Miss McCagh by throwing petrol over her, throwing petrol over a bed in the house and setting fire to her, whereby she was so severely injured that she died later that day in Ninewells Hospital, Dundee, and he murdered her, having previously evinced malice and ill will towards her.

Solicitor General Frank Mulholland QC suggested to Ms Peplar a scenario in which 17-year-old Jessica was on the bed in the room, sitting at the corner the bed was against, and petrol was poured over her.

The quantity of petrol was sufficient to run down the wall and accumulate below the bed. After it ignited the door was shut and damage was caused to the handle as a result of the door being held shut.

The witness said her observations were “entirely consistent with that.”

She estimated the amount of petrol required to account for the damage she saw in the bedroom of the couple’s flat to be “at least a litre, probably more.”

In support of her findings, she said, “It is not particularly easy to pour petrol out of a jerry can because the opening is quite narrow. You get glugging.

“It is quite difficult to get a significant amount of liquid out of the can. It is much easier to throw it,” she added, demonstrating by holding the container by the handle and base and moving both arms back and forward.

Ms Peplar said she examined the flat on May 1 to determine the origin and cause of the fire.

There was a very distinct ‘V’ pattern on the wall at the top left-hand corner of the bed. That indicated this was the seat and the shape of the ‘V’ indicated that the fire had burned rapidly.

The materials of the bed —the mattress, wooden surround and pillows, if any —were not sufficient in themselves to produce that shape, she told the court.

Because she had been told that Jessica McCagh had been at that point on the bed and because of the presence of petrol on her clothing, the witness said, “It would be a logical inference to say there would be petrol on that area of the bed.”

There was a localised area of burning at a low level, close to the point of origin, and there was “no reasonable scientific explanation for such damage to occur naturally.” It was her opinion that petrol had travelled down the wall and accumulated at that point.

The ‘V’ pattern from the point of origin extended over the door, indicating it had been shut when the fire took hold. There was damage to the facing of the door frame but the inside of the frame was “a lot cleaner.”

Plastic from a smoke detector on the ceiling above the door had melted and residue was found on the bedroom side of the door handle.

“If the door was open there would not have been enough smoke and heat to melt the smoke detector,” Ms Peplar said.

The living-room side of that handle had damage which, in her opinion, was “mechanical damage” not accounted for by fire but by physical force.

She said there was a secondary area of burning, close to the bedroom side of the door, which could not be explained as a second seat of fire. She interpreted this as someone with their clothes alight standing there and burning material dropping down and starting the secondary fire.

From the severity of the damage in the bedroom it was her view that the fire had produced heat rapidly.

If the door was closed it would contain the heat and the temperature (of the fire) would be higher than it would be if the door were open.

She said the door had also been in the open position during the fire but in her opinion this was “probably near the end.”

The witness agreed when Mr Mulholland suggested the bedroom door had been closed for the majority of “the flaming fire.”

Examination of the bedroom window and the area outside provided no evidence that there had been an explosion.

Ms Peplar estimated that the petrol would have to have been out of the can and vaporising in the room for “maybe a couple of minutes” before ignition to create an explosion.

She tested for the presence of accelerants and to identify any accelerants found in clothes taken from Blackburn and Jessica.

From the accused’s tracksuit bottoms a probe recorded 13 parts per million from the evidence bag they were in 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.”

Ms Peplar 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.

“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 that 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 alight.

Jurors were also shown a filmed series of experiments designed to replicate ways in which the fire could have started.

A jerry can was “slapped,” causing spillage of petrol on to a top on a manikin; 50ml of petrol was measured out and poured on to the top; and finally half a litre was poured on to it.

At each stage commercially produced cigarettes, hand-rolled cigarettes and cannabis joints attached to a puffer machine were held by an extended rod, close to and directly against the petrol-stained garment.

All failed to ignite the different quantities of petrol.

It was only when the naked flame from a cigarette lighter was placed close to the area of saturation that the petrol ignited, with increasing effect with each quantity.

Ms Peplar said that even then the flame had to be about a centimetre from the saturation before the fire started, “Which, I have to admit, surprised me.”

She said the explanation put forward by the accused for the fire starting—an ember from a cannabis joint falling on to the spilled fuel —was “so unlikely it can be dismissed.”

Earlier, defence counsel said there were lies, truths and unsolved mysteries in the statements Stewart Blackburn gave to police after he was detained.

Detective Constable Gary Simpson, on his third day in the witness box, agreed that was true when the suggestion was put to him by Neil Murray QC.

Mr Murray put it to the witness that Blackburn had told lies during the three interviews the detectives conducted over the course of the weekend following Miss 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 girlfriend.

He referred to Blackburn’s statement in which he said he grabbed pots, cups and looked for wet towels to pour water over her.

He referred the officer to a photograph of the hallway taken after the fire was extinguished and he 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 Blackburn running past him as soon as he got in the door.

Mr Murray said the witness recounted Jessica in flames collapsing against the doorway. In one of his statements to police the accused also described her 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 roiling from that flat, asked Stewart 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 Mr Foreman at the time he was interviewing the accused.

The officer agreed he had seen the statement and 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.”

The trial continues.