The decision follows a US television documentary in which two doctors said they believed Matthew Eappen was strangled, and not shaken by the former au pair as charged by prosecutors.

Her lawyers admit they do not know if the theory is reliable, but they have initiated a scientific investigation to re-examine how Matthew died at his home in Boston, Massachusetts.

Woodward, 21, from Elton, Cheshire, was convicted in October 1997 of second-degree murder.

She appealed and the judge reduced her conviction to involuntary manslaughter and released her from a Massachusetts jail. She is now a law student in London.

Strangulation theory

Lawyer Harvey Silvergate said the defence team would have its own experts review the strangulation theory and then approach prosecutors to see if they could jointly launch an independent inquiry.

The result could lead to a motion for a new trial, but lawyers said that decision would depend on the findings and would need Woodward's sanction.

She told 60 Minutes, broadcast by CBS on Sunday, that it was "only a matter of time" before medical evidence proved she did not kill Matthew.

But the prosecution team that led the case against Woodward has denounced the new claims.

And a group of more than 70 physicians has criticised the CBS report, describing it as "preposterous". They also questioned why one of the doctors behind it had been paid by the defence team.

'Artery squeezed'

But Mr Silvergate said the doctors dismissing the claims were mostly paediatricians and not "hard scientists".

However, another defence lawyer, Barry Scheck, said Dr Nelson had been paid $700 before the trial by the defence team. He was never called as a witness.

He said: "His contribution was minimal. It is, in fact, Dr Giles who is the main proponent of the strangulation theory."

Dr Floyd Gilles, a neuropathologist, and Dr Marvin Nelson, a radiologist, at Children's Hospital in Los Angeles reviewed the medical records of Matthew at the request of 60 Minutes.

Dr Gilles concluded Matthew's neck injuries suggested he had been strangled.

He said a neck artery may have been squeezed as much as 48 hours before the child collapsed, causing his brain to swell slowly.

Mr Scheck added: "Miss Woodward has always taken the course that would vindicate her and prove her innocent."