Woburn, MA--2/28/2013--Christina Hancock (cq), 26, of Acton, pleads guilty to involuntary manslaughter in the May 12, 2010 killing of her 13-month-old son Kaydn Hancock, in Middlesex Superior Court, on Thursday, February 28, 2013. Judge Maureen Hogan (cq) sentenced her to eight to 10 years. Photos by Pat Greenhouse/Globe Staff Topic: 01acton Reporter: Brian Ballou
Christina Hancock pleaded guilty to killing her son.
Pat Greenhouse/Globe Staff

WOBURN — After insisting for almost three years that her 13-month-old son died of an accident, Christina Hancock pleaded guilty today to a charge of involuntary manslaughter, bringing an end to the case and allowing Hancock to avoid prosecution for first-degree murder.

Hancock was sentenced in Middlesex Superior Court to eight to 10 years in prison. Judge Maureen Hogan called the death of a child at the hands of his mother “tragic.’’

Under an agreement with Middlesex District Attorney Gerard T. Leone Jr., Hancock pleaded guilty to involuntary manslaughter, which carries a maximum sentence of 20 years behind bars. She was originally charged with first-degree murder, which carries a maximum sentence of life imprisonment without the possibility of parole.

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Middlesex prosecutors recommended a sentence of eight to 10 years.

Hancock, 26, of Acton, pleaded not guilty in August 2010 to charges that she beat her son, Kaydn Hancock, to death on May 12 of that year.

Prosecutors said Hancock dialed 911 around 4:30 a.m. that day and said her son had fallen out of the crib and hit his head. The child was taken from Hancock’s home on Great Road and rushed to Emerson Hospital in Concord, where he was pronounced dead at 5:17 a.m., authorities said.

Hancock, wearing loose gray sweatpants and a forest-green top, stood and accepted the plea deal before shuffling to the witness stand in her leg shackles. Once on the stand, Hancock answered a series of standard legal questions from Hogan.

When Hogan asked her if she knew why she was in court, Hancock replied, “for my third child who has passed away.”

During the question and answer session between judge and defendant, several of Hancock’s relatives sobbed.

Hancock said that when she was 13 or 14 years old, she was diagnosed with bipolar disorder. She said she had symptoms until age 18. She said she graduated from high school and worked as a cashier.

Deborah Bercovitch, Middlesex County assistant district attorney, read off a list of injuries Kadyn suffered, including contusions to the stomach, colon, lung and liver, some of which were pre-existing or in a state of healing, suggesting the boy had suffered prior beatings.

A medical examiner ruled the cause of Kadyn’s death as “blunt force trauma to the torso,’’ prosecutors said.

When police interviewed Hancock in the hours after the death, she told them she woke to the sound of a bang and then saw her son lying on the floor. She said she splashed water on his face and attempted to feed him Cheerios, but the boy wasn’t chewing.

Kadyn’s father, Lamar Woodard, submitted a written statement to the court.