A 70-year-old woman pleaded guilty today to second-degree murder in the suffocation deaths of eight of her children over 19 years beginning in 1949, ending decades of speculation over what caused the deaths of so many infants in one family.

Marie Noe, a frail, white-haired woman, had long maintained that the children died mysteriously of crib death. Today, Noe admitted she killed her babies and was sentenced to 20 years of probation, the first five years to be served under house arrest with electronic monitoring. Under the plea agreement, entered today in Philadelphia's Court of Common Pleas, she also will undergo psychiatric treatment.

"I think it's a fair resolution of the case," said David Rudenstein, Noe's attorney. "And while facing her responsibility is emotional and troubling for her, I believe she's at peace with her decision and looking forward to taking part in mental health treatment to try to find the causes of her past behavior.

"She's grateful for probation so she can be with her elderly husband."

Philadelphia District Attorney Lynne Abraham, who reopened the cases in 1998 after they had been dormant for 30 years, said she thought probation for Noe was the appropriate sentence.

"It's obvious some people would have undoubtedly wanted to have Mrs. Noe in prison," Abraham said in an interview. "Given her age and the uncertainty of what the judge might do, it was the best we could hope for."

Investigators started reexamining the deaths of Noe's children last year in light of several factors, Abraham said, including the publication of a book, "The Death of Innocents," in which authors Richard Firstman and Jamie Talan maintained that some cases of child homicides may be wrongly attributed to Sudden Infant Death Syndrome, especially where multiple children in families were involved. That book, and publicity generated by Noe's case, triggered scrutiny of infant death cases across the country, especially in cases where the cause of death was attributed to SIDS.

Noe's children, ranging in age from 13 days to 14 months, died during the years 1949 through 1967, all while alone at home with their mother. The unlikely string of deaths had been attributed over the years to crib death, now known as SIDS, a term that was used to describe unexplained cases where seemingly healthy babies died in their sleep.

"Our hope is that because of Marie Noe pleading guilty, medical examiners and coroners throughout the country will look more carefully into the circumstances surrounding babies' deaths," deputy district attorney Charles F. Gallagher said yesterday.

Gallagher said he didn't think such a case involving so many children could happen today. "I think by the second or third child, the medical examiner, investigators and police would get involved," Gallagher said.

In addition to the eight who died in her care, Noe gave birth to two other children, one of whom was stillborn and another who died shortly after birth while in the hospital. For decades, Marie Noe was pitied as a woman who lost 10 children and was featured in Life magazine in 1963 as researchers sought to find explanations for SIDS.

There had been suspicions for years that Noe was involved in the deaths of her babies. But Abraham said it was only recently that medical science and better knowledge of SIDS caught up with those suspicions.

Noe, who lives with her husband, Arthur, in a working-class neighborhood of small rowhouses, was charged with murder in August. She had acknowledged in a statement to police last spring that she suffocated at least four of the children. Arthur Noe, who was in court today to hear his wife plead guilty to killing eight of their children, steadfastly had defended his wife against the accusations.

Investigators are hoping the court-ordered psychiatric treatment will shed some light on why Noe killed her children. Rudenstein said at the time of the deaths Noe was suffering from blackouts and possibly mental illness. "My feeling from dealing with her is that there was something wrong . . .," he said. "In other parts of her life, she led a normal life, but with the children something triggered these actions."

CAPTION: Marie Noe and her husband, Arthur, leave the probation office in Philadelphia after she received 20 years of probation for pleading guilty to smothering eight of her children.