"She was warm as toast and never, ever, ever too busy to devote what seemed like all the time in the world to the lowliest, us residents," said Sarah Long, who arrived at St. Christopher's Hospital for Children as a resident in 1970 and who has been chief of infectious diseases for 35 years. "Her owlish glasses would fall down her nose as she was doing an autopsy. She would push them back with a great big smile and tell you something she had just noticed."
In 1944, when Dr. Valdés-Dapena graduated from Temple University School of Medicine, "pathology was the top of the medical profession," said M. Daria Haust, professor emerita at the University of Western Ontario; pathologists found the diseases.
St. Christopher's, at the time Temple's teaching hospital for pediatrics, was an international leader in pathology. But hardly anything was known about postmortems on infants.
Moonlighting at the Philadelphia Medical Examiner's Office, Dr. Valdés-Dapena encountered "crib deaths": babies who went to sleep healthy and were dead in the morning, with no clues to be found during autopsies. She had investigators visit homes, and put pins on a big map to find patterns.
It was one of the earliest scientific examinations of what later became known as sudden infant death syndrome. In the 1960s and '70s, Dr. Valdés-Dapena was a leading researcher and the chief debunker of various SIDS theories, from viruses to milk allergies. Many such deaths are still unexplained, but after recommendations in the 1990s that babies be placed on their backs to sleep, mortality plummeted.
One idea she got wrong was the theory that sleep apnea caused SIDS and that baby monitors could prevent it.
Another was in the Marie Noe case.
Between 1949 and 1968, eight of Art and Marie Noe's babies died mysteriously at home. In 1958, Dr. Valdés-Dapena performed the autopsy on Constance Noe, baby No. 5, and she observed or assisted on all the later Noe cases.
Though it may seem obvious today, the idea that a mother could kill her child was alien then. "I remember hearing her saying a mother could not do that," said Dr. Valdés-Dapena's daughter Victoria Pendragon.
Although primitive forensics could not distinguish accidental crib death from intentional suffocation, suspicions ran high within the Medical Examiner's Office. And 30 years after the last Noe child death, a book about SIDS briefly quoted Dr. Valdés-Dapena saying "it was likely a case of multiple murder."
That prompted Stephen Fried to investigate. His reporting for Philadelphia Magazine in 1998 led police to reopen the case. Noe later confessed.
Dr. Valdés-Dapena already had some dementia when she helped close the case. "Her learning curve formed the world's learning curve," said Fried, who called her "heroic."
Born Marie Agnes Brown on July 14, 1921, in Pottsville, she quickly became Molly; colleagues later called her "Dr. Molly." Her father wanted his children to be doctors.
"I said, 'Daddy, I couldn't do that. When you go to medical school they make you go and look at dead bodies, but I couldn't do that. I'd drop over in a faint,' " she said in 1999.
When she graduated from Immaculata College, however, her father took her to Temple medical school.
She met "a tall, dark, and handsome Cuban chap" in a doctors dining room, and soon married pathologist Antonio Maria Juan Hedwiges Valdés-Dapena Y'Galtes.
It was understood that she would give up her career if he asked.
They raised their children in The Castle, a stone mansion in Wallingford. Pathology was everywhere. "There were home movies of autopsies," son Peter said.
In 1976, her husband announced a move to Florida - with his mistress, it turned out. His wife went anyway, but Antonio soon divorced her; he died in 1992. She spent most of the next 21 years teaching at the University of Miami School of Medicine and practicing at Jackson Memorial Hospital. She retired in 1996 and returned to the Philadelphia area.
Although known for her work with SIDS, she had a broader impact.
"She fought for mothers to be able to hold their [dead] child," letting them grieve, said her daughter Cris.
And she was ahead of most in the field in recognizing the signs of battered children and speaking out about child abuse as the modern child-protection system emerged.
Besides Victoria of Paw Paw, W. Va.; Cris of Bermuda; and Peter of New York City, she is survived by children Debi of Los Angeles; Andres of Hanover, Pa.; Carlos of Vienna, Va.; Mark of Toledo, Ohio; Antonio of Spotsylvania, Va.; Dan of Media; Patty Fater of Cape Cod, Mass.; and Cate of Kennett Square; 21 grandchildren; and five great-grandchildren.
No funeral is planned. Arrangements for a memorial service were incomplete.
For stories about Dr. Marie Valdés-Dapena - and her most famous case, serial baby-killer Marie Noe, go to
Contact Don Sapatkin at 215-854-2617 or firstname.lastname@example.org.