A judge today sentenced Alyssa Bustamante, the teenager who strangled and stabbed her 9-year-old neighbour to death, to life in prison.

Bustamante was 15 when the crime occurred three years ago in St. Martins, near Jefferson City, Mo. An entry in her diary called the experience “ahmazing.”

She spoke again about that night before a judge sentenced her in a Missouri courtroom.

“I really am extremely, very sorry for everything," she said, according to The Associated Press. “I know words can never be enough, and they can never adequately describe how horribly I feel for all of this.

“If I could give my life to get her back I would. I'm sorry.”

By pleading guilty to second-degree murder, Bustamante avoided an adult sentence without parole. She will serve consecutive 30-year terms for an armed criminal act. Bustamante strangled Elizabeth Olten unconscious before slitting her throat and stabbing her in the chest.

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Prosecutors described her as a thrill killer while the defense portrayed her as a mentally disturbed child. Both families were in court, but didn’t give statements to the press.

“The sentencing process was extremely difficult for the family, as no sentence can adequately punish this heinous crime," said Matt Diehr, a lawyer representing Olten’s parents.

Bustamante lured the young girl into the woods, where a shallow grave waited, the prosecution said. While initially lying to police, an entry in her diary led to a confession.

"I strangled them and slit their throat and stabbed them now they're dead," Bustamante wrote in her diary, ABC News reported. "I don't know how to feel atm (at the moment). It was ahmazing. As soon as you get over the 'ohmygawd I can't do this' feeling, it's pretty enjoyable. I'm kinda nervous and shaky though right now. Kay, I gotta go to church now...lol."

The defense told the judge that drug-addicted parents left Bustamante with her grandmother. The girl tried to commit suicide upon entering Grade 8 and was on a high dose of Prozac at the time of the killing, Reuters said.

“This was a child who had been spiraling out of control, but has treatable conditions," defense lawyer Charlie Moreland told the AP.

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