The deaths of a woman's three babies could have been caused by a genetic disorder inherited from her grandmother, who lost five children in early infancy, an expert in genetics told a court yesterday.

Michael Patton said the evidence "strongly suggested" that there was a genetic disorder in Trupti Patel's family that could account for the sudden deaths of her children.

Professor Patton told Reading crown court he believed the deaths of three of Mrs Patel's maternal grandmother's children were relevant to the fate of her own babies.

Mrs Patel's grandmother, Surajben Patel, 80, from Gujarat, India, told the hearing on Wednesday that she had lost five of her 12 children within six weeks of their births.

Trupti Patel, 35, a qualified pharmacist, denies murdering her sons, Amar and Jamie, and her daughter, Mia, none of whom survived beyond the age of three months.

All three collapsed suddenly at the Patel family home in Maidenhead, Berkshire, in separate incidents between 1997 and 2001, and later died.

Prof Patton, a consultant in clinical genetics at St George's hospital, part of the University of London, said the evidence appeared to show that the deaths of two of Mrs Patel's grandmother's children were not relevant to the case.

He said it appeared that one had died because she was born prematurely while another was killed by gastroenteritis.

However, he said the other three deaths were relevant to the question of whether there was a genetic disorder in the family that could account for the deaths of Trupti Patel's three babies.

"We have three deaths here in which infection did not seem to play a part and in which prematurity did not play a part, so I think they are unexplained deaths," he said.

Prof Patton said Mrs Patel's grandmother could have had a genetic disorder, and that there were several mechanisms by which the defendant could have inherited it.

If Surajben Patel had a dominant abnormal gene, this could have been passed down to her granddaughter through autosomal dominant inheritance.

"I believe that this is relevant in this situation," he said. "What we would be doing is linking the three deaths in the grandmother's family and the three deaths in Trupti Patel's family. Obviously the abnormal gene would have had to have passed through Trupti Patel and her mother without manifestation."

Prof Patton said Trupti Patel could have inherited a genetic disorder known as Long QT syndrome - a disorder which affects the rhythm of the heart and which can cause sudden death.

Another mechanism, known as mitochondrial inheritance - in which an abnormal gene is contained within a mother's egg - could also account for Trupti Patel inheriting a disorder.

The case continues.