MARIETTA — “Guilty,” Seron Shepherd said, her voice cracking.

Shepherd pleaded Thursday to the involuntary manslaughter of her infant son, whom she put to sleep in a baby swing next to a space heater on a cold night in December 2009 when the family lived on Ling Drive in Austell.

“I’m living with this every day, the loss of my son,” Shepherd, 31, told Cobb Superior Court Judge George Kreeger. “I miss my other children. I accept responsibility for what happened.

“I would like to ask for mercy.”

Her plea was not negotiated. Prosecutor Chuck Boring asked for 10 years, with five to serve. Shepherd’s court-appointed attorney Jill Stahlman asked for probation, or a sentence of less than 12 months, which would keep her out of the state prison system.

She was ordered to serve three years in prison and remain on probation for seven years thereafter.

“This is a tragic set of circumstances,” Stahlman said. “She knows she made a grievous mistake and that nothing she is going to say or do will bring her son back.

“This was not intentional. Her interest was in keeping her son warm. It was very cold outside. The family had little financial resources. They used space heaters because the child’s father had complained about high utility bills. She’s a good mom.”

Shepherd is the mother of three other children who were ages 7, 4 and 21 months at the time that seven-month-old Keron Brown died. The children are now in foster care and Shepherd has been allowed supervised visits with them. Shepherd, who told the court she has a 10th-grade education, wore a bright purple pantsuit to the hearing and was taken into custody immediately afterward.

Prosecutor Boring painted a different picture of Shepherd, who was the only adult in the home that night.

“On the evening of Dec. 5, 2009, Ms. Shepherd put her children to bed. She put Keron in a battery-operated swing and put a space heater very close to the swing,” he said. “The house had functional central heating. During the evening, the seven-year-old boy thought the room was too hot and turned the heater off. Ms. Shepherd scolded the seven-year-old and turned the heater back on. At some time in the night, the swing stopped working, and the child was left there.”

Boring said the seven-year-old boy woke up about 7 a.m. and noticed something was wrong with the baby. The baby’s father had by then come home from work and went with the older boy into the bedroom, where he discovered the baby dead.

Keron Brown died of second- and third-degree burns and heat exposure.

Cobb Police were called to the Austell home and found the three oldest children had been sleeping on the floor, the home did not have adequate food, and the children were filthy.

The baby’s father told police that he had warned Shepherd that the space heater was not safe and could get too hot.

“This wasn’t just an accident,” Boring told Judge Kreeger. “This is somebody who turned a complete blind eye to the condition of her house and her children.”

Before imposing sentence, Judge Kreeger told Shepherd that “no greater responsibility can be placed upon one than caring for children. Conduct which allows something like this to happen is not excusable.”

She will also serve concurrent 12-month sentences for misdemeanor counts of contributing to the deprivation of each of the other three children. Kreeger denied a defense request for first-offender status, which would have allowed the entire case to be discharged after Shepherd served the sentence and probation without any trouble.

Once out of prison, she likely will be allowed supervised visits with her children, but is to have no contact with anyone younger than 18.