Emily Bazelon, a senior editor at Slate, said the following in an NPR interview:
"It used to be that the assumption was that every time you had evidence of the shaking -- medical evidence -- that you knew, you assumed that the baby would immediately stop breathing and go into a coma ...
Now doctors acknowledge ... that in at least a few cases it's possible for a child to remain conscious for some amount of time."
This throws into question whether the last caretaker was always the abuser. In addition, says Bazelon, the symptoms that used to be considered an assurance of shaken-baby syndrome could possibly be caused by bleeding disorders or certain accidental falls.