A mother and a stepfather have been charged with murdering her 10-year-old daughter who was allegedly beaten so badly, she suffered brain damage and slurred speech before her death.

Sharon Carrillo, 33, and the dead girl's stepfather Julio Carrillo, 51, have been charged with murdering Marrissa Kennedy in Stockton Springs, Maine.

The girl was found unresponsive at around 2.30pm on Sunday (25 February) at a condo complex on Harbor View Drive.

Sharon Carrillo and Julio were arrested the next day at state police offices in Bangor after being interviewed by detectives and both face one count of depraved indifference murder.

The Sun Journal reported that the couple told police that they punished the girl by forcing her to kneel on a tiled floor where she was whipped anywhere between 10 and 15 times with a leather belt or struck with their bare hands.

They allegedly told investigators that they chose the tiled floor because it would hurt more and they also admitted that they kept the child in a dark closet as a punishment.

It is alleged that the girl was beaten from October until February to the point that the girl could no longer walk or speak, without slurring her words, say police.

Julio said he stopped beating Marrissa believing his wife beat the girl because she thought the child was faking her injuries, it was alleged.

The Carrillos' two other children, aged one and two, had been staying at the home at the same time and the Maine Department of Health and Human Services has taken them into custody.

The Daily Mail reported that an autopsy determined the girl's death was a homicide but authorities have not revealed her official cause of death.

According to the Sun Journal a medical examiner said Marrissa had suffered bleeding on the brain and a lacerated liver in the weeks before her death.

The couple are due to appear in court on Wednesday (28 February).