A specialist in neuro-pathology, Jan Leestma, said that his examination of the brain of Matthew Eappen, the child Ms Woodward is accused of killing, showed evidence of an injury suffered weeks before he was rushed to hospital in an ultimately fatal coma.
The testimony, elicited by Barry Scheck on the defence bench, appeared to constitute the very linchpin of the defence's case that the cause of death pre-dated 4 February, the day the prosecution says Ms Woodward violently shook the child and slammed his head against a hard surface.
The implication may be that the child suffered an earlier episode that either went undetected or was concealed by his parents. It will be enough for the defence, however, simply to create sufficient doubt in the minds of the jurors about the charges against Ms Woodward of a "cruel and atrocious" assault.
Dr Leestma's observations, which he sought to illustrate with a series of blown-up photographs of slides of brain tissue presented to the jury, directly contradicted the testimony of several medical experts brought earlier by the prosecution that the cause of death was so-called "shaken baby syndrome".
Earlier, the jurors heard from the head teachers of the high and primary schools attended by Ms Woodward close to her Chester family home. The highly sympathetic words offered by both witnesses represented the first attempts by the defence to blunt the often damaging testimony offered earlier in the trial by prosecution witnesses about her alleged fondness of late nights and unreliability as a child-minder.
Under hours of examination by Mr Scheck, Dr Leestma said at the outset that his findings, established after he was given access to the formaldehyde- preserved brain of Matthew last month, demonstrated beyond reasonable doubt two facts that could prove crucial if an acquittal is to be finally delivered in the case.
They were first, that a blood clot existed between the brain and brain lining - called the dura - before 4 February and had probably been there for three to four weeks. He also asserted that he saw evidence of re-bleeding in the area of the sub-dural clot which can be assumed to have been the cause of the neurological collapse suffered by the then eight-month-old boy and his death on 9 February.
Asked by Mr Scheck what kind of event would have been necessary to trigger the fatal re-bleeding - in other words an event caused by Ms Woodward - he replied, "It may take almost nothing". He added: "The capillaries are so thin and delicate they just rupture." Dr Leestma, who practises at a brain institute in Chicago, told the jury that the presence and the age of the original clot was evidenced first by a third membrane on the surface of the dura when there should only be two. Moreover, the thickness of that neo-membrane dated the occurrence of the clot to about 3-4 weeks before 4 February.
"We've got a third membrane that is not supposed to be there," the doctor said, pointing to areas of tissue on the photograph and highlighting them with a marker pen. He also pointed to what he said was evidence of calcium deposits. Such deposits, he said, accumulate during a period of perhaps three weeks after some trauma is suffered by the human brain.
On the pivotal issue of parts of the brain and dura apparently lost during autopsy, Dr Leestma said they could have been crucial in identifying the pre-existing clot. "This was really the bullseye of the medical problem that was going on," he said, adding that the loss likewise of the clot itself was similarly unfortunate.Reuse content