MIAMI • An eight-year-old boy who beat a baby girl to death to stop her crying while her mother was out partying at a nightclub has been charged with murder.

The boy was one of several children left alone for hours in a Birmingham, Alabama, home last month, in what experts said was a rare case of a child so young being prosecuted.

"Since becoming a police officer over 22 years ago, this is by far one of the saddest cases I have witnessed in my career," Birmingham police spokesman Lieutenant Sean Edwards said on Wednesday.

The incident happened at the home of a friend of the baby's mother, whom police have identified as 26-year-old Katerra Lewis.

She has been charged with manslaughter over what Lt Edwards called "reckless" actions.

Police said Lewis left her one-year-old, Kelci, together with several children aged two to eight, while she and her friend went out clubbing. The children - six in total, according to local media - were left unsupervised while Lewis and the friend were gone from roughly 11pm until 2am.

"It is believed that while the mother and friend were at the club, the eight-year-old viciously attacked the one-year-old because the one-year-old would not stop crying," police said in a statement.

"The one-year-old suffered from severe head trauma as well as major internal organ damage which ultimately led to her death."

The mother told police on the morning of Oct 11 that she found the baby unresponsive in her crib. The baby was treated at the scene by first responders and was later pronounced dead at a children's hospital.

"No education, no school, no degree, no training can really prepare you for an eight-year-old committing a heinous crime like this," said Lt Edwards.

The mother was released on US$15,000 (S$21,300) bail. The Department of Human Resources (DHR) said it had no prior complaints concerning Lewis or her daughter.

The DHR is holding the boy and will not release his name.

The boy will be tried in juvenile court and risks being sentenced to juvenile prison until up to age 21 if found guilty, said lawyer Tobie Smith, who specialises in the defence of minors.

Last month, an 11-year-old boy from Tennessee was charged with first degree murder after he shot and killed his eight-year-old neighbour following an argument over a puppy.

AGENCE FRANCE-PRESSE