(AP) - Alyssa Bustamante looked down, her long brown hair covering her teenage eyes, as a judge read the charges against her: murder and armed criminal action, for knowingly strangling, cutting and stabbing her 9-year-old neighbor. For more than two years after she was arrested as a high school sophomore, Bustamante had been publicly silent about the gruesome crime, which a patrol officer testified she confessed to committing because "she wanted to know what it felt like." On Tuesday, it was her time to talk. Describe what you did, a judge instructed Bustamante, as she pleaded guilty to second-degree murder for killing Elizabeth Olten. "I strangled her and stabbed her in the chest," Bustamante said in a clear voice, looking straight at the judge. She used her hands for strangling and a knife for the rest of the attack, Bustamante told judge. Sitting a few feet away in the front row of a cramped courtroom, her helpless victim's mother took a deep breath and dabbed her tears. She was angry, frustrated, sorrowful. Bustamante had been charged with first-degree murder, and by pleading guilty to a lesser murder charge she avoided a trial and the possibility of spending her life in an adult prison with no chance of release. Cole County Circuit Judge Patricia Joyce will decide after a Feb. 6 sentencing hearing how long Bustamante should remain locked up. Her sentence could be as short as 10 years, or as long as life with the possibility of parole after about 25 years. Elizabeth's mother, Patty Preiss, wore a purple shirt with a photo of her daughter and the entreaty: "Justice for Elizabeth." She left the courthouse with several similarly dressed relatives and friends, and none of them talked to reporters. "They're disappointed that parole is now a possibility," family attorney Matt Diehr later told The Associated Press. It's kind of devastating to relive the event and hear some of what was said in the courtroom today. Bustamante killed Elizabeth on Oct. 21, 2009, and after two days of searching for Elizabeth by hundreds of people, Bustamante led police to her victim's well-concealed body in the woods behind their neighborhood in St. Martins, a rural community just west of Jefferson City. Prosecutor Mark Richardson declined to comment after Tuesday's hearing about why he agreed to a reduced charge, adding that he wouldn't talk about the case until after Bustamante's sentencing. Several factors could have influenced the reduced charges. Last summer, the judge ruled that part of Bustamante's 2009 confession to authorities could not be used at trial because a juvenile officer wrongly participated in the state Highway Patrol interview and "used deceptive tactics." The legality of sentencing teenage murderers to life without parole is also in question, and the U.S. Supreme Court is scheduled to hear arguments in March on whether it amounts to cruel and unusual punishment. Although the arguments in that case focus on a pair of 14-year-olds convicted in Arkansas and Alabama, the outcome could have also been applied to Bustamante's situation. "That may have made them more willing to give a plea deal that took that sentence off the table," said Ben Trachtenberg, an associate law professor at the University of Missouri-Columbia who teaches courses on criminal court procedures and evidence. Had the case gone to trial, the arguments likely would have focused on whether the crime amounted to first- or second-degree murder, which does not require the same degree of deliberation, he said. Moreland added: "She had a lot of issues at that time." Juvenile justice officials testified at a November 2009 hearing that Bustamante had attempted suicide at age 13 after receiving mental health treatment for depression and cutting herself. She had sometimes spent the night in the woods without permission and had once sneaked away to St. Louis. But Bustamante also ranked in the top third of her class at Jefferson City High School and had not been in any previous trouble with the law, other witnesses said. At that 2009 hearing, prosecutors said Bustamante carefully planned to kill Elizabeth. They said she dug two holes to be used as graves, then attended school for about a week while waiting for the right time to kill. Missouri State Highway Patrol Sgt. David Rice testified that the teenager told him "she wanted to know what it felt like" to kill someone.