Leigh Matthew Frederick Beer. Photo: RNZ / Robin Martin
A fatal New Plymouth fire started on a mattress that was exposed to a naked flame, a specialist forensic fire investigator has told a jury.
Leigh Matthew Frederick Beer is on trial, charged with arson and murder following the death of 21-year-old Emma Field in May 2022.
The 31-year-old is also charged with assault with intent to injure.
The Crown alleged after an evening of drinking and drug-taking, Beer tipped over a bed which Field was sleeping in, set the mattress alight and left her to burn to death.
Beer has denied the charges, his defence team arguing the case against him is circumstantial and someone else could have lit the fire.
Emma Field. Photo: NZME
On Monday, the jury heard from specialist forensic fire investigator, Russell Joseph, who re-constructed the fire scene.
He said based on all known factors, the mattress was set on fire between 10.50pm and 10.53pm "with a naked flame being introduced to a flammable material" long enough that the ignition would be self-sustaining.
The Crown alleged Beer set the fire using a combination of a cigarette lighter and butane lighter after being left outside the Devon Street West address at 10.46pm by mates who went into town without him.
It said CCTV footage shows him going back into the flat in the divided villa where his partner had earlier gone to bed - upset at his antics at the get-together.
Joseph told the jury he reached his conclusion about where the fire started after systematically ruling out other common sources of ignition including wall sockets, multi-boards, appliances, lights, candles and cigarettes.
There was no evidence of an accelerant having been used.
Once alight, he said, the fire would have taken five-to-eight minutes to reach "flashpoint or full fire" but it would have already started to migrate into the hall and towards the flat's second bedroom.
Joseph said there was the potential for Field to have left the bedroom in the first couple of minutes of the blaze, but that "after three minutes it was non-survivable".
It would also have been possible to put the fire out with a fire extinguisher or a fire hose in its early stages, he said.
Joseph's reconstruction, however, showed Field had little chance of getting out of the room.
Field was found on her back facing up at the ceiling while squashed between the exterior wall and the overturned bed and mattress - which she was partially trapped under - and hemmed in by a dresser.
Joseph said people found facing up after fires were either dead before the blaze began or unconscious.
Those found facing down may have made and an attempt to escape.
He did not think Field had tried to escape.
Joseph said the queen-sized bed and mattress could only have been flipped over from the bedroom door side of the room and with quite some considerable force.
This was supported by where the wooden bed slats were found distributed on the bedroom floor, he said.
The undersides of the slats were not burned - nor was the carpet under them - which Joseph said was evidence the bed had been flipped before the fire was set alight.
Defence attorney Julian Hannam had few questions for the forensic fire investigator.
But he did want to know whether Joseph could rule out - using patterns of smoke damage - whether or not the front door was closed while the fire was burning for a period of time.
The fire investigator said he could not for a "limited period of time".