WARNING: Some readers may find the details of this story distressing

A woman killed in a fire allegedly lit by her partner was effectively trapped in the bedroom where the blaze broke out.

Leading specialist fire investigator Russell Joseph gave evidence on Monday as the trial of murder-accused Leigh Matthew Frederick Beer entered its fourth week.

The 33-year-old is defending charges of murder, arson and injuring with intent to injure in the High Court at New Plymouth.

It is alleged he murdered his partner Emma Field, 21, on May 27, 2022, at their New Plymouth flat by overturning the bed on which she was sleeping and setting fire to it.

Joseph said Field was found lying on the floor between a wall, the bed and mattress, which was partly on top of her, and a dresser.

Her only way out was climbing over the bed, which was on fire, or around the back of it, where space was restricted.

Joseph, a former detective sergeant who now runs Corporate Risks Ltd, also concluded Field would have had a couple of minutes to try and escape the blaze but after that, it was non-survivable.

“This fire would have taken upwards of one-and-a-half to two minutes to transition from the incipient stage to the fire growth stage,” he said.

“During that incipient stage, although there would be a lot of smoke, a person would be capable of leaving a room, provided they were not standing.”

However, no attempts were made by Field to flee, Joseph said.

He determined that based on the position of her body, she was unconscious at the time of the fire.

A forensic pathologist previously gave evidence that a post-mortem showed she was still breathing after the fire started, and her cause of death was the effects of incineration.

Following his investigation, Joseph concluded the fire began at the foot of the bed in the couple’s master bedroom between 10.50pm and 10.53pm before spreading to other areas of the house.

He found the bed had been overturned and the mattress was partially on Field’s body.

Based on the bed’s position and where Field was located, it could not have been her who moved it, he said.

“You also have to look at the weight of the bed and the mattress combined and evaluate the amount of effort and force that would be required to lift and turn the bed and mattress simultaneously.”

Joseph’s investigation determined the fire did not begin due to an electrical outlet or appliance, lightbulb or the filament of a lightbulb, a cigarette, or a candle.

In his expert opinion, that left only an open flame being applied to the flammable material.

In response to a question by Crown prosecutor Cherie Clarke, Joseph confirmed a cigarette lighter, which was found on Beer, or a butane gas lighter, which was at the scene and had his DNA on it, would have been sufficient to have started the fire.

However, the flame would have needed to have been held to the material until “it was capable of sustaining its own combustion”, he added.

Joseph also referred to a suggestion made by Beer in a police interview that a lightbulb had previously exploded in the couple’s bedroom and the filament had landed on their bed and started a fire.

“That is not possible,” Joseph said, explaining it would not have retained sufficient heat energy to be a competent ignition source for a fire.

ESR scientist Janina Hopkins spoke about Beer’s blood being found at the flat, including in the kitchen and lounge and on items such as a teatowel.

Outside, blood was found on stairs, a hose reel, on the lawn, Beer’s car, and on a butane gas lighter discovered by the hose.

Hopkins said if there was blood staining in the master bedroom, it could not be detected due to the damage caused by the fire.

The Crown alleged that before the fire started Beer was angry and talking about suicide when he “out of the blue” punched a glass panel in his front door.

Two of his friends have said in evidence they were there when that happened and gave him a teatowel to put around his bleeding hand then left, leaving Beer at the house and the front door open.

But Beer has claimed he smashed the front door, and other windows at the property, after the fire started.

He maintained the door was closed and locked so he punched the glass panel and reached through to open it.

Beer said he then ran inside but when he got into the lounge he could not breathe due to the heat, and he could see “glowing” down the hallway, so he returned outside.

The officer in charge of the investigation, Detective Sergeant Paula Drewery, was called this afternoon as the Crown’s final witness.

She confirmed under cross-examination that not all empty alcohol cans found in the kitchen of the couple’s flat following the fire had been examined for DNA.

While the Crown points the finger at Beer, alleging he killed Field in a fit of rage following a night of drinking alcohol and drug-taking, defence has maintained someone else could be responsible.

The trial before Justice Karen Grau continues tomorrow when the defence is expected to call evidence, followed by the closing arguments.

Tara Shaskey joined NZME in 2022 as a news director and Open Justice reporter. She has been a reporter since 2014 and previously worked at Stuff covering crime and justice, arts and entertainment, and Māori issues.