INDIANAPOLIS -- A medical examiner's conclusion that a newborn baby's death was caused by the rat poison her mother ate while she was pregnant is unreliable and cannot be used against the woman at her murder trial, an Indiana judge has ruled.

Prosecutors have argued all along that Shanghai native Bei Bei Shuai killed her child by eating rat poison in December 2010, when she was eight months pregnant. But Marion County Judge Sheila Carlisle said Dr. Jolene Clouse, who performed the autopsy on newborn Angel Shuai, didn't consider other possible causes for the brain bleeding that caused the baby's death, including a drug that Shuai received while she was in the hospital.

A spokeswoman said Wednesday that prosecutors are still reviewing Friday's ruling, but it seemed to undermine the linchpin of their case.

Carlisle wrote that Clouse consistently repeated her stand that the rat poison Shuai ate caused her daughter's death, but never said how she knew it was rat poison and not indomethacin, a drug given to pregnant women that can have a similar effect. Carlisle said Clouse also never considered that brain bleeds occur often in premature infants without any clear cause. She said Clouse's methodology was flawed.

"The opinion of Dr. Clouse on the cause of A.S.'s death is therefore unreliable," Carlisle wrote in the ruling issued Friday.

Shuai's attorney, Linda Pence, said the decision was "significant."

"It was based upon the substantive evidence we presented during hearings that showed the state cannot establish causation," Pence said Wednesday.

Shuai was eight months pregnant when she ate rat poison on Dec. 23, 2010, after her boyfriend broke up with her. She was hospitalized and gave birth to Angel on Dec. 31. The baby died three days later. Prosecutors who charged Shuai with murder and feticide in March 2011 contend Shuai meant for her then-unborn child to die with her.

The case in Indiana has drawn international attention from reproductive rights advocates who claim it could set a precedent by which pregnant women could be prosecuted for smoking or other behavior that authorities deem dangerous to their unborn child.

"It also highlights the practical reasons why pregnant women should never be subjected to prosecution of this type. The relationship between a pregnant woman and the fetus she carries is the most complicated relationship we have in nature," Pence said. "Newborns and fetuses die of complications often and typically doctors cannot even answer why it occurred, it just happens."

Shuai was released on bond last May. Her trial is set for April 22.

At the time of the autopsy, Clouse had about 2 1/2 years of experience as a forensic pathologist with the Marion County coroner's office. She is currently a professor of forensic pathology at the Indiana University Medical School in Muncie.

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    Bei Bei Shuai is charged with murder in the Jan. 2, 2011, death of her 3-day-old daughter Angel Shuai.

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    Bei Bei Shuai, 35, right, Indianapolis, hugs her friend, Sue Mock, second left, as attorney Linda Pence, left, looks on after Shuai's release on bail from the Marion County Jail in Indianapolis on Tuesday, May 22, 2012. Shuai faces a December trial on charges of murder and feticide. Shuai, a Shanghai native, ate rat poison in a suicide attempt in December 2010 when she was 33 weeks pregnant. Her baby was delivered by Caesarian section and died three days later. The case has drawn the attention of medical and women's rights groups who say Shuai's prosecution endangers the rights of pregnant women and could prevent women from seeking prenatal care out of fear of criminal charges.

  • Bei Bei Shuai

    Bei Bei Shuai, 35, right, of Indianapolis, leans on her attorney, Linda Pence, as she leaves the Marion County Jail in Indianapolis on bail Tuesday, May 22, 2012. The case has drawn the attention of medical and women's rights groups who say Shuai's prosecution endangers the rights of pregnant women and could prevent women from seeking prenatal care out of fear of criminal charges.

  • Bei Bei Shuai, Sue Mock

    Bei Bei Shuai, 35, right, Indianapolis, hugs her friend, Sue Mock, after Shuai's release on bail from the Marion County Jail in Indianapolis on Tuesday, May 22, 2012.