Police found Dena Schlosser, 37, covered in blood in her kitchen, still holding a knife and listening to a church hymn.
During opening statements, her attorney said Schlosser clearly did not know right from wrong during the November 2004 slaying of baby Margaret.
"This is somebody who at the time was not capable of knowing what she was doing was wrong," defense attorney William Schultz said. "She didn't see it coming. ... Normally Dena is a sweet woman. She cares, she has compassion."
Prosecutor Curtis Howard disagreed, saying that while Schlosser obviously had mental problems, she did know right from wrong when she killed her daughter.
"At some point that morning, Dena Schlosser put Maggie Schlosser down on the bed and cut off her arms," he said.
The first witness was Steve Edwards, the 911 operator who took Schlosser's call. In a tape of the conversation, Schlosser could be heard calmly describing her actions. When Edwards asked her if there was an emergency, she responded "Yes."
"Exactly what happened?" Edwards asked.
"I cut her arms off," Schlosser replied as a hymn played in the background.
"You cut her arms off?" he repeated.
"Uh-huh," she answered.
As the tape played, Schlosser slumped in her chair and pressed her chin into her chest, staring down at her hands.
Schlosser was diagnosed with manic depression after her arrest. In February 2005, a jury deliberated only a few minutes before deciding Schlosser was mentally incompetent to stand trial and she was committed to North Texas State Hospital in Vernon. But in May, a judge decided Schlosser was competent.
Her two surviving daughters, ages 6 and 9, are in their father's custody.
Schlosser had been accused of child neglect in the months before Margaret's death, but a state investigation found she did not pose a risk to the baby or her other two daughters.
Texas' troubled Child Protective Services came under intense scrutiny after a number of high-profile child abuse deaths, including the Schlosser case.
The Health and Human Services Commission, which oversees CPS, laid out more than 160 recommendations last year to overhaul the agency.
By Julia Glick