DAYTON, Ohio (AP) — A former cellmate of a woman accused of killing her month-old baby by burning the girl in a microwave testified Thursday that the woman confessed to the crime, saying the baby "fit right in" the oven.

Linda Williams testified that she developed a sexual relationship with defendant China Arnold when the two were cellmates in the Montgomery County jail in March and that Arnold confided in her about what happened to her baby.

She said Arnold feared that her boyfriend believed he wasn't the child's father and that he was going to leave her.

"She said she put the baby into the microwave and started it and left the house," Williams said.

Williams said she asked Arnold how she got the child into the oven.

"She said she fit right in," Williams said.

Sitting at the defense table, the 27-year-old Arnold showed little emotion as her trial got under way in the August 2005 death of Paris Talley at their Dayton home.