The disturbing reason a 10-year-old girl is facing life in prison.

WARNING: This story includes details that readers may find distressing.

A 10-year-old girl is facing the possibility that she will serve a life sentence in prison after she was charged over the death of a six-month-old baby.

Though she’s only in primary school, the Wisconsin girl is currently being tried as an adult over the shocking crime.

So what happened?

A horrific incident

On October 30 at around 4.30pm police were called to a house in the Wisconsin town of Tilden, where a home daycare also operated.

There had been an incident of some sort and a six-month-old baby boy had somehow suffered serious head injuries. Investigators say there was one adult and three children at the home at the time.

The little boy, who was unresponsive and bleeding from his head, was taken to St Joseph’s Hospital and later flown to Gillette Children’s Specialty Healthcare. Sadly, the infant, who hasn’t been named, could not be saved and died two days later on November 1.

What Chippewa County District Attorney Wade Newell now alleges is that a 10-year-old girl is responsible for the baby’s death, ABC 5 Eyewitness News reports.

He alleged the girl, who hasn’t been named, dropped the boy accidentally and he hit his head on a footstool. When he began to cry, she stomped on his head, prosecutors say.

“She panicked, didn’t know what to do and didn’t want to get into trouble,” Newell said in court.

The 10-year-old, who had been living in the home under foster care, initially told authorities she hadn't injured the boy, but allegedly later confessed in interviews with police, the New York Daily News reports.

The daycare has remained shut, and so far no one else has been charged in relation to the baby's death.

A child in court

Under Wisconsin law, the 10-year-old girl has been charged with first-degree intentional homicide by someone age 10 or older.

It is one of several states in the US that treat young children as adults when charged with murder.

"By statute, a 10-year-old or older is required to at least start out the process in adult court, and that’s why we’re here today," the judge explained on Monday at the girl's bail hearing.

This doesn't mean, however, that the girl's case will stay in adult court. It may be transferred to juvenile court. Her charges may also be downgraded from the very serious Class A first-degree intentional homicide.

The key to this charge is that the accused intended to kill the victim with their actions, and therefore that it was not an accident.

That's what Chippewa County Sheriff James Kowalczyk alleged in court.

"The injuries sustained by the six-month-boy was not an accident," he said.

However, another charge of first-degree reckless homicide exists in the state. To be found guilty of that Class B felony, prosecutors need only prove that the accused "recklessly caused the death of another human being under circumstances which show utter disregard for human life".

For now though, the young suspect is facing the possibility that, if she is found guilty, she will be given a mandatory sentence of life imprisonment, with or without parole.