One of the biggest discrepancies in how SIDS cases are diagnosed is in the greater Los Angeles area.

More than three-quarters of all infant deaths in L.A. are labeled vaguely as "ill-defined or unknown causes." But in the city's northern neighbor, upscale Ventura County, three quarters of all infant deaths are labeled as SIDS.

"It is no longer fashionable to call sudden infant death cases a result of SIDS," said Dr. Ronald O'Halloran, chief medical examiner for Ventura County. "But I still see a statistical usefulness in making a diagnosis of SIDS, but I'm not surprised to hear that others are not."

O'Halloran said some coroners are frightened by the diagnosis.

"It's the risk of embarrassment, of making a call of SIDS and finding out later that someone killed a baby," he said.