Experts claim that shaken baby syndrome has well-defined symptoms that clearly distinguish it from injuries caused, for example, by falling.

When a baby is violently shaken, tiny blood vessels in the brain can start to bleed. The brain becomes bruised and swells. Small bleeds can occur in the retina at the back of the eye, and bigger ones between the membranes covering the brain.

These changes are diagnosed by identifying bleeding in the retina, or subdural haematoma (blood in the brain), or increased head size caused by accumulation of fluid in the brain.

Damage to the spinal cord and broken ribs from grasping the baby too hard are other symptoms. X-ray or MRI scans can be used to detect these changes.

The effects on the baby can be mild or severe, depending upon the intensity of the shaking. Considerable force must be used to cause enough damage to produce the brain changes used to diagnose the condition.

In recent years the theory has come under pressure from sceptics who say that the symptoms supposedly unique to shaken babies can be seen in others who have had a fall, choked on their food or simply suffered an infection.

Since no trials can be carried out to show that the injuries can only be caused by shaking, the usual defence is that the injuries were accidental. Experiments suggest that an impact causes angular accelerations more than 50 times greater than shaking. It is the accelerations that cause the damage.

Those sceptical about shaken baby syndrome argue that retinal bleeding can have several causes, not simply shaking. Jennian Geddes, of the Royal London Hospital, looked at 50 babies who had died and found that 36 had suffered the kind of bleeding in the brain believed characteristic of shaken baby syndrome. Of these, three quarters showed signs of reduced oxygen in the blood. This suggests that a lack of oxygen, caused by infection, asphyxia or choking, can cause the brain to swell, and that bleeding is secondary.

Twelve expert witnesses called by the prosecution

Susan Downes Registered as doctor in 1997. Graduated from Bristol University in 1996. Specialist in ophthalmology since July 1997

Pieter Pretorius Graduated from the University of the Orange Free State in 1993 and registered in July 1995. Specialist in clinical radiology since September 2004

Wilhelm Kuker Graduated in 1987 from the Christian Albrechts Universität in Kiel and registered as a specialist in clinical radiology in 2004

Michael Pike Graduated from the Royal College of Surgeons in 1977. Specialist in neurology and paediatrics since July 1996

Nathaniel Carey Graduated from the University of London in June 1981. Specialist in histopathology from October 1996

Steven Gould Graduated from University of London in 1977. Histopathology specialist since 1996

Warey Squier No record on GMC register

Brendon McDonald Graduated from the University of Liverpool in 1982. Specialist in neuropathology from 1997. Entered GP register in 2006

Jonathan Kay Graduated from Royal College of Surgeons in 1977. Specialising in chemical pathology since June 1996

Neil Stoodley Graduated from Oxford in June 1985 and has been a specialist in clinical radiology since October 1997

Safa Al-Sarraj Graduated from University of Baghdad in 1981. Registered in 1992. Specialist in histopathology since November 1996

Professor Rupert Risdon Graduated from Royal College of Surgeons in 1962. Became a specialist in histopathology in 1996

Source: General Medical Council’s list of registered medical practitioners

Explore Health

• Expert Advice

• Health Features

• Mental Health

• Alternative Medicine

• Child Health

• Health Club