Updated

An appeals court overturned the conviction of a baby sitter on Thursday and ordered a new trial, saying the latest research into shaken baby syndrome might prove she didn't kill a baby in her care.

The woman, Audrey Edmunds, was convicted in 1996 of reckless homicide in the death of 7-month-old Natalie Beard. Edmunds, who had been baby-sitting the girl, was sentenced to 18 years in prison.

In her appeal, Edmunds, 46, argued that recent developments in medical research into shaken baby syndrome cast doubt on her conviction. The District 4 Court of Appeals agreed Edmunds has presented enough new evidence to win a new trial.

A fierce debate has developed over whether babies can die through shaking alone, whether they can stay alive for a time after receiving traumatic head injuries and whether symptoms similar to those associated with shaking can be caused by other factors, the court said.

"The main issue at trial was the cause of Natalie's injuries, and new medical testimony presents an alternate theory for the source of those injuries," Judge Charles Dykman wrote for the three-judge panel.

The appeals panel said the new evidence undermined their confidence in the jury's original conviction but "does not completely dispel the old evidence" used to convict her. A jury should weigh the competing opinions of medical experts in deciding the case, Dykman said.

"There is a reasonable probability that a jury, looking at both the new medical testimony and the old medical testimony, would have a reasonable doubt as to Edmunds's guilt," he wrote.

Prosecutors have 30 days to appeal to the Wisconsin Supreme Court.

"We're disappointed," said Kevin St. John, a spokesman for the Wisconsin Department of Justice, which will determine whether to appeal after consulting with Dane County District Attorney Brian Blanchard. "The state stands behind the arguments that it made in the Court of Appeals."

Blanchard said it was too early to say whether prosecutors would retry the case, drop it or appeal. He declined comment on whether he would oppose bail for Edmunds.

Keith Findley, a Wisconsin Innocence Project lawyer who is representing Edmunds, called on prosecutors to drop the case and release her.

"I would hope they would, after all this time and given there really is no evidence against Audrey Edmunds other than this now very dubious scientific evidence," he said.

Findley said he would file a motion as early as Friday seeking to have Edmunds released on bail.

The baby appeared healthy when dropped off at Edmunds' in-home day care on Oct. 16, 1995 but Edmunds testified she quickly became fussy. She later found her limp with liquid, apparently formula, coming out of her nose and mouth. Edmunds called 911 and the baby was pronounced dead hours later at a hospital.

Prosecutors contended at her trial the baby died from violent shaking or shaking combined with impact that caused a fatal head injury. A pathologist testified the injuries were consistent with shaken baby syndrome.

The defense contended the baby might have been shaken to death but that the injury could have occurred before she was dropped off.

Edmunds filed her latest appeal in 2006, citing the new research and arguing the baby could have died from a number of other causes, such as choking on formula, seizures or an infection.

Findley said the ruling was among the first from a state appellate court to recognize the new research and reverse a conviction. At the time of Edmunds' 1996 trial, doctors who raised such questions were viewed as extremists, he said. Now, they are in the mainstream.

"It's an enormous decision for Audrey, but I also think it's absolutely the right decision," Findley said. "It's the just outcome in this case."