He did admit that he had carried out his own research into cot death in infants - a subject on which he was a world authority - without seeking the coroner's permission, but says very little of this was carried out on children's bodies.

BBC: The pathologist

The advice given by FSID on how to reduce the risk of cot death remains the same - parents are urged to put their babies to sleep on their backs, and smoking by parents both in pregnancy and afterwards near the child is discouraged.

BBC: 'Lowest ever' infant death rate

Three-week-old Marc Clynes died 15 years ago from cot death.

BBC: Child's brain 'thrown away'

It is difficult to prove - for prosecution or defence - that, in the face of these uncertainties, an individual cot death was either definitely due to abuse, or definitely not.

BBC: NEWS | Health | The science behind cot deaths