Darci Pierce could not stop herself from killing Cindy Lynn Ray, who was nearly nine months pregnant when her child was cut from her body, a psychiatrist testified.

Dr. Jean Goodwin of Milwaukee testified Tuesday that Pierce was legally insane when the slaying occurred.Pierce is charged with first-degree murder, kidnapping and child abuse in the July 23, 1987, death of Ray, 23.

Pierce is charged with abducting Ray from the parking lot of a Kirtland Air Force Base health clinic, driving her to the Manzano Mountains east of Albuquerque and cutting the baby from the victim's body with a car key. The baby girl, Amelia, survived.

Pierce, 20, has pleaded not guiltyby reason of insanity. Her attorneys are not denying the allegations, but contend Pierce was not sane at the time.

Goodwin testified for the defense that Pierce suffers from an atypical dissociative disorder, which is characterized by a person's inability to connect their experiences with their hundreds of thoughts. The amnesia Pierce experienced following the slaying is part of the syndrome, she said.

The psychiatrist also testified that Pierce has multiple alternating personalities.

New Mexico law defines legal insanity as the result of a mental disease. It states that a person can be classified as legally insane if he did not know what he was doing or understand the consequences of his act; did not know the act was wrong; or could not prevent himself from committing the act.

Goodwin said Pierce suffers from a mental disease.

Dr. Susan Brayfield-Cave has diagnosed Pierce as having a mixed personality disorder. She said Pierce suffers from a dissociative disorder that clouds her perception of reality.

Brayfield-Cave agreed with Assistant District Attorney Harry Zimmerman that a personality disorder is by itself not a mental disease under New Mexico law.

Zimmerman suggested that Pierce suffers from a specific personality disorder and therefore cannot be found not guilty by reason of insanity.