Chicago

A WOMAN calls 911 to report that a baby in her care has gone limp. Rescue workers respond immediately, but the infant dies that night. Though there are no external injuries or witnesses to any abuse, a jury convicts the woman of shaking the baby to death.

More than 1,000 babies a year in the United States are given a diagnosis of shaken baby syndrome. And since the early 1990s, many hundreds of people  mothers, fathers and babysitters  have been imprisoned on suspicion of murder by shaking. The diagnosis is so rooted in the public consciousness that, this year, the Senate unanimously declared the third week of April “National Shaken Baby Syndrome Awareness Week.”

Yet experts are questioning the scientific basis for shaken baby syndrome. Increasingly, it appears that a good number of the people charged with and convicted of homicide may be innocent.

For the past 30 years, doctors have diagnosed the syndrome on the basis of three key symptoms known as the “triad”: retinal hemorrhages, bleeding around the brain and brain swelling. The presence of these three signs (and sometimes just one or two of them) has long been assumed to establish beyond a reasonable doubt that the person who was last taking care of the baby shook him so forcefully as to fatally injure his brain.