Some experts say that when a baby suffers bleeds to the brain and the eye it must have been violently shaken.
Cases of 'shaken baby syndrome' are increasing
But fresh research challenges the science behind Shaken Baby Syndrome, so that some doctors now think that the syndrome doesn't even exist.
No-one doubts that people do abuse, even kill their children, but what disturbs some doctors are those "shaken baby" cases where there is no evidence of previous abuse: no broken bones, no bruises, no scars.
Reporter John Sweeney and the Real Story team that helped free cot death mother Angela Cannings investigate how the courts and the police may be bringing "shaken baby"cases on disputed medical opinion - raising the possibility that people have gone to prison for murders that never actually happened.
Reporter John Sweeney writes about the programme:
Real Story: BBC One, Monday 29 March 2004, 1930 BST and live on the Real Story website.