A 15-year-old girl strangled and stabbed her 9-year-old neighbour to death because 'she wanted to know what it felt like to kill."

Alyssa Bustamante, who will turn 18 later this month, pleaded guilty to killing Elizabeth Olten in 2009 and faces up to life imprisonment.

Prosecutors said that Bustamante plotted the death of her neighbour, even digging two holes to bury her in advance.

When pleading guilty, Country Circuit Judge Patricia Joyce asked the girl to explain what she did.

"I strangled her and stabbed her in the chest," she replied.

"Did you cut her throat too?'' the judge asked.

"Yes," Bustamante responded.

Mother of the murdered Elizabeth took a deep breath on hearing Bustamante's answers whilst wearing a pink shirt with "Justice for Elizabeth" on the front.

The judge set a February 6 date for sentencing, commenting that the killer could face life imprisonment should she be found guilty of first degree murder. However, should they find her guilty of second degree murder; she could get between 10 and 30 years with a view of parole.

Juvenile justice officials said in court that Bustamante had attempted suicide at the age of 13 and had received mental health treatment for depression and self-harm.

Missouri State Highway Patrol Sergeant David Rice told the court she had confessed the killing and showed the police to her grave. He also said that the girl "wanted to know what it felt like'' to kill someone.