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, did not consider other possible causes for the brain bleeding that resulted in the baby’s death, including a drug that Shuai was given 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.

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 clearly meant for her then-unborn child to die with her.

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