Lawyers for the Irish nanny, who is accused of killing a baby girl in her care last year, have filed a hard-hitting challenge to testimony from a medical specialist which implicated her in the tot's death.
Aisling Brady McCarthy, 35, from Lavey in Co. Cavan, is facing first degree murder charges over the death of one-year-old Rehma Sabir, who died in Boston in January last year.
The tot was diagnosed as having being the victim of abusive head trauma - or Shaken Baby Syndrome - when she was rushed to Boston Children's Hospital, having been in the care of McCarthy.
But in a dramatic new development McCarthy's lawyers have challenged those findings and insisted that "an avalanche of science" had exposed such diagnoses as unreliable.
In court documents filed late last Wednesday, her defense team wrote: "At best, SBS [Shaken Baby Syndrome] is a highly controversial, unproven hypothesis unfit to serve as the basis for a murder prosecution.
"At worst, SBS is junk science, a tragic hoax caused by overzealousness within the child protection community."
The Boston Globe reports that scientific doubts as to the reliability surrounding Shaken Baby Syndrome have prompted McCarthy's legal team to seek a hearing on the evidence.
In their documented challenge to the testimony, her lawyers stressed: "This is a shaken baby prosecution. That means it is a prosecution based on a scientific hypothesis that has crumbled over the past decade."
Baby Sabir, who authorities say was in McCarthy's exclusive care when she was injured, was diagnosed by Dr. Alice Newton, the medical director of the child protection program at Boston Children's Hospital.
Newton - who prosecutors plan to call as an expert witness in the case - stated that the child had suffered shaken baby syndrome the day after she was taken into hospital. The following day the baby was declared brain-dead and her life support machine was switched off two days later.
But in the latest court development, McCarthy's lawyers wrote that the diagnosis was made despite the fact that the infant had an "extensive history of medical problems" and "despite the lack of any outward evidence that she had been abused".
They also claimed that there was no evidence that Newton or other doctors "spent any meaningful time" attempting to find alternative diagnoses.
In their motion, they also point out that that the child had in the past been examined by specialists for a range of worrying conditions, including gastrointestinal problems, failure to put on weight and a bleeding disorder.
They also highlighted medical records, which indicate that the tot was diagnosed with malnutrition five weeks before her death and "by all accounts bruised very easily".
They continued: "When [Rehma] died, her body had no bruises, grip marks, crush injuries or acute broken bones. Yet, the Commonwealth alleges that medical science proves that she died because the last person with the child, Ms. McCarthy, violently shook her or caused her abusive head trauma. Not so."
Her defense team also highlighted the fact that prosecutors had initially charged the Irish nanny with inflicting verterbral fractures, but later concluded the injuries were more likely to be three to four weeks old - which was a time when the baby was travelling with her mother in Pakistan.
The Boston Globe also notes that the defense team filed a separate motion, which casts doubt over Dr. Newton's expert opinion in a "strikingly similar" case, which resulted in Middlesex prosecutors indicting Geoffrey Wilson in the 2010 death of his six-month-old son.
However, the Irish nanny's lawyers have discovered that Wilson has not yet gone to trial and that the medical examiner's ruling that his son's death was a homicide has not been recorded on his revised death certificate.
In their motion the defense team asked to be provided with all the medical information - particularly records involving Newton - to clarify "why the major legal question of how the child died in the Wilson case is suddenly altered".
McCarthy's trial is not expected to take place until October this year.