Constance Marten’s newborn baby would have been exposed to “substantial climatic cold stress” in the first few days she spent camping on the South Downs in January 2023, a jury has heard.
Professor George Havenith, an expert on clothing and cold exposure, told the jury that baby Victoria would have been at a “substantial risk of hypothermia.”
Marten and the baby’s father Mark Gordon are in the middle of a retrial at the Old Bailey in London.
They deny causing or allowing the death of a child and gross negligence manslaughter.
In their first trial they were found guilty of concealing the birth of a child and perverting the course of justice by not reporting the death of their baby.
The court has heard that they went on the run after police found a placenta on the back seat of their car, which had caught fire on the M62.
After travelling by taxi from Liverpool, they spent two nights at hotels in Harwich and another night in a taxi driving from London to Newhaven in Sussex.
They then walked out onto the South Downs with a tent from Argos and two summer sleeping bags.
It was raining at the time and the temperature over the next few days was about 7.5C.
The baby’s decomposing body was found in a plastic bag in a shed on a Brighton allotment almost two months later.
Prof Havenith told the jury he had conducted a number of experiments in a climate chamber at Loughborough University to recreate the conditions inside and outside the tent.
He said that the tent was a bit warmer than the outside air temperature: “Inside the tent it gets up to five degrees (centigrade) higher than the outside,” he said.
However, he said that with no mattresses, anyone lying on the floor of the tent would have been colder.
“The tent itself has virtually no insulation on the ground,” he said.
He also conducted an experiment in which he asked two PhD students to sit inside the tent and found that within an hour they saw “water running down the tent walls”, caused by the condensation of their breath.
Joel Smith KC, for the prosecution, asked if baby Victoria could have kept warm inside Constance Marten’s coat if everything had remained dry.
“With a dry coat, dry clothing, dry sleeping bag, there would be just enough insulation to keep the baby safe,” Professor Havenith said.
But then he was asked what would have happened if the clothing was wet.
“Baby Marten, in the conditions studied, 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,” he said, quoting from the conclusion of his report.
Mark Gordon and Constance Marten deny all charges.
Prof Havenith evidence continues.
