Kansas City, Mo. ? A neuropsychologist’s report says brain scans indicate that a woman accused of cutting the baby from a northwest Missouri woman’s womb suffers from a mental illness that caused her to believe she was pregnant.

But federal prosecutors Tuesday challenged the scientific credibility of the report – which has not been made public – and other evidence defense attorneys plan to present at Lisa Montgomery’s federal trial to show the Melvern, Kan., woman is mentally ill.

Montgomery, 39, is charged with kidnapping resulting in death in the slaying of 23-year-old Bobbie Jo Stinnett in Skidmore, Mo. She is accused of strangling Stinnett, who was eight months pregnant, at Stinnett’s home Dec. 16, 2004.

Prosecutors say Montgomery then cut a baby girl from Stinnett’s womb and returned to Kansas, where she paraded the girl around as her newborn daughter before she was arrested in Melvern.

The child was returned to her father, Jeb Stinnett.

U.S. District Judge Gary Fenner will decide what evidence he will allow at Montgomery’s trial, which is scheduled to begin in October. If convicted, Montgomery will face the death penalty.

Her attorneys have said they will use an insanity defense. On Tuesday, they cited several conditions – including post-traumatic stress disorder, depression and impulsivity – from which they say Montgomery suffers.

The focus Tuesday was on a condition called pseudocyesis, a false belief of being pregnant that sometimes is accompanied by signs such as abdominal enlargement, engorged breasts and labor pains.

A University of Pennsylvania professor hired by the defense to perform MRI and PET scans of Montgomery’s brain appeared to have found abnormalities consistent with pseudocyesis.

But a prosecution expert and professor of neurology at the Montreal Neurological Institute said there is no evidence of such a condition.

Alan Evans testified Tuesday that from his review of the data, Montgomery’s brain is very close to normal. He said using brain imaging technology to diagnose a person’s mental disorders is controversial.

He said abnormalities spotted by the Pennsylvania professor could be nothing more than typical physical and functional variations researchers find in the human population.