Constance Marten’s baby could have been exposed to a “substantial risk of hypothermia” in a tent on the South Downs, an expert has said.
Marten, 37, and Mark Gordon, 50, are accused of the manslaughter of their daughter Victoria who died after they went off-grid in early 2023.
The Old Bailey has heard how the couple had gone to the south coast to avoid their fifth child being taken into care amid a high profile police hunt for the missing baby.
It is alleged Victoria was inadequately clothed in a babygrow and that Marten had got wet as she carried the baby underneath her coat.
The prosecution allege Victoria died from hypothermia or was smothered while co-sleeping in the “flimsy” tent on the South Downs, despite past warnings.
The child’s body was discovered with rubbish inside a shopping bag for life in a disused shed near Brighton after the defendants were arrested on February 27 2023.
On Tuesday, jurors heard evidence from a chartered ergonomist who conducted experiments on the risk of hypothermia to Victoria.
Professor George Havenith, from Loughborough University, examined conditions as the defendants travelled to the South Downs and inside the tent once there.
He told jurors that he took account of the temperatures between January 8 and 10 2023 as well as the impact of wind and moisture.
As well as conditions inside and outside the tent, he also examined the microclimate between layers of clothing worn by Marten, the court was told.
Prosecutor Joel Smith KC asked: “If the baby were wearing only a babygrow with those temperatures either outside or inside a tent without a sleeping bag, what would be the risk of hypothermia?”
The witness replied that the risk “would be very high”.
Mr Smith said: “You looked at the sleeping bags purchased by Gordon. In your view, were they fit for the conditions?”
The witness replied: “No.”
Asked about the impact of not having a mattress, he told jurors that it was an “essential” item and a sleeping bag was not an effective insulator.
Prof Havenith said an adult in a dry tent would have avoided hypothermia but would find it “very uncomfortable”.
He added: “Wet clothing reduces your insulation quite substantially. It means you will have to shiver harder. The stress on the adults would become bigger.”
An experiment with two PhD students – in appropriate clothing – breathing in a tent resulted in condensation running down the walls and on the floor, the court was told.
Prof Havenith told jurors: “Based on experience I would expect condensation to occur.
“It would not directly affect temperature, but water on walls and floor will be absorbed by clothing. I would expect the clothing to absorb more moisture.”
He told jurors that if Marten’s clothes and sleeping bag had remained dry, there was “just about enough” insulation to keep the baby safe.
Mr Smith asked: “If the temperature goes down, clothing gets wet, sleeping bag gets wet, do we have enough?”
Prof Havenith replied: “No.”
Asked about his overall conclusions, Prof Havenith said: “Baby Marten, in the conditions stated, especially where moisture was present in the clothing both in the tent and on the way to the South Downs, would have been exposed to substantial climatic cold stress which would have led to a substantial risk of hypothermia.”
Marten and Gordon, of no fixed address, have denied the gross negligence manslaughter of their daughter and causing or allowing her death between January 4 and February 27 2023.
Jurors have been told the defendants were convicted at an earlier trial of concealing the birth of a child and perverting the course of justice.
The trial continues.