Alejandro rushed to a neighbor's house, carrying Lucas in his arms. The baby was barely breathing, his skin clammy and ashy-gray. His eyes rolled back in his head, and milky fluid came out of his mouth.

The neighbor called 911, then tried mouth-to-mouth resuscitation. Lucas vomited. State College police arrived and took over, one officer trying to clear the child's airway and later doing chest compressions when paramedics showed up.

An ambulance took the baby to Centre Community Hospital in State College. His father stayed behind to answer questions from police.

In the emergency room, doctors found retinal hemorrhaging in Lucas' eyes. His fontanel - the soft spot on the head where a baby's growing skull has not yet closed - was bulging, indicating some kind of pressure on his brain. He had no reflexes.

A chest X-ray revealed a fracture in the lower left rib, and what the doctors thought was calcium forming between the ribs and sternum.

It was evidence, they believed, of multiple healing fractures. Evidence of abuse.

They shared their suspicions with police, who searched the family's three-bedroom house that afternoon.

Two days later, a doctor analyzed a repeat X-ray and saw something odd: There was no evidence of calcium formation after all. He concluded that, with the exception of the one fracture, the previous findings were "artifactual" - inaccurate. And later analysis would determine that the one fracture was old - with no connection to the baby's sudden collapse.

But by that time, Lucas had been helicoptered 80 miles away, to Geisinger Medical Center in Danville - home to a level-one trauma center with special accreditation for pediatric cases.

The diagnosis of child abuse was well on its way.

Death and doctors

Physicians coined the term shaken-baby syndrome in the early 1970s to describe a collection of symptoms that included retinal and brain hemorrhages, but not necessarily any external signs of head trauma.

The internal bleeding and other damage are thought to occur from a whiplash effect, made possible because an infant has weak neck muscles and a head proportionately larger than an adult's.

Some researchers and judges have begun to question whether shaking alone - without impact against a hard surface - is enough to kill a baby. This can't be proven by shaking an actual infant, so researchers study lifelike models.

But the mainstream medical view is that shaken-baby syndrome is all too real, and sometimes deadly - the tragic result when a caretaker simply becomes too frustrated to cope with a wailing infant.

One symptom attributed to shaking, called retinoschisis, is said to involve jelly inside the eye that is attached to the retina. If the eye is shaken back and forth, the jelly moves one way while the outer part, including the retina, moves in the other direction.

Blood vessels tear, and the retina is pulled away from its accustomed position, developing unnatural "folds." Some doctors have maintained that such folds can be explained only by shaking; that certainty is now in question.

Two days into Lucas' stay at Geisinger, doctors recorded that he had this problem in his eyes. The rib fracture worried them, too, though tests suggested it was not new. And he was bleeding inside his brain.

The baby's parents maintained a bedside vigil - when they were allowed. Child-welfare officials had decreed the couple could not see Lucas without medical staff present.