DAYTON, Ohio (AP) — A mother intentionally put her month-old daughter in a microwave oven and cooked the child to death after a fight with her boyfriend, a prosecutor told jurors Thursday.

Defendant China Arnold and her boyfriend had argued over whether he was the biological father, Assistant Montgomery County prosecutor Daniel Brandt said during closing arguments in the woman's three-week retrial. The argument got so intense that Arnold bit her boyfriend's lip and he slapped her, Brandt said.

Arnold later told a cellmate she put the infant in the microwave and turned it on because she was worried her boyfriend would leave her if he found out the child wasn't his, Brandt said.

"She could have stopped it with one finger, but she didn't," he said. "We know she used that microwave as the instrument of death."

Arnold, 28, of Dayton, has pleaded not guilty to a charge of aggravated murder in the 2005 death of Paris Talley and could face the death penalty if convicted. A judge declared a mistrial in Arnold's first trail earlier this year.

Jurors in the retrial deliberated for about four hours. They were to be sequestered Thursday night and expected to resume deliberations Friday.

Defense attorney Jon Paul Rion told the jury Thursday there was evidence that someone else was responsible.

He cited Tuesday's testimony from an 8-year-old boy who said he saw another boy walk into the kitchen of a nearby apartment with the baby, heard the microwave go on, and then later saw the burned baby in the microwave.

"He told a very believable story," Rion said. "There wasn't any question in his mind."

With the small black microwave oven sitting just feet from the jury, Assistant Montgomery County prosecutor David Franceschelli said Arnold intentionally put her baby inside.

Prosecutors said the baby was cooked in the microwave for at least two minutes. Franceschelli pretended to turn the microwave oven on and then held up his watch to the jurors, counting down the time in increments of 30 seconds.

"Would you push it (off) now? Now?' he asked the jurors. One began fidgeting. Another dropped his gaze to the floor.

Prosecutors said the baby's DNA was found inside the microwave in Arnold's apartment, and Arnold's cellmate testified during the first trial that Arnold confessed. The cellmate's videotaped testimony was shown at the retrial.

Judge John Kessler declared a mistrial Feb. 11 after he privately heard testimony from the juvenile who testified Tuesday.

In rebuttal, the 8-year-old's mother testified Wednesday that they lived some distance away and they were not at Arnold's apartment complex when the baby died. Her former live-in boyfriend also testified that he was certain the boy was not at the location.

"Sometimes kids make up things," Franceschelli said.

As she entered the courtroom earlier Thursday, Arnold smiled and waved to family members. At times during the prosecution's arguments, she shook her head in disagreement and also glared at a police detective who had questioned her during the investigation.

Rion told the jury that the maternal instinct is the strongest of human instincts and that it defies logic that Arnold would kill her baby. He said police investigators targeted Arnold from the beginning and made it their objective to build a case against her.