One of two Wisconsin girls who stabbed a classmate in 2014 — in the name of a fictional Internet horror character known as Slenderman, they later claimed — made her first appearance in front of a jury on Tuesday.
Sixteen jurors, eight men and eight women, were selected Monday in Waukesha County, Wisconsin, to decide whether 15-year-old Anissa Weier suffered from a mental illness at the time of the attack more than three years ago, the Milwaukee Journal Sentinel reports.
If a jury finds Anissa was mentally ill, she will go to a state mental hospital and not seek to be released for three years, according to local TV station WISN. If the jury decides she did not suffer from a mental disease, prosecutors could then recommend a 10-year prison sentence out of a maximum possible 25 years.
“Anissa’s broken mind caused her to lose touch with reality,” her attorney, Joseph Smith, told jurors in court on Tuesday, according to the Associated Press. “Anissa was under the command and control of a delusional disorder.”
Prosecutors argued differently, the AP reports, saying Anissa and friend Morgan Geyser “knew this was wrong, they understood what they were doing was wrong.”
Anissa and Morgan lured Payton Leutner to a local park on May 31, 2014, where they stabbed her 19 times, prosecutors have said. All three girls were 12 years old.
Payton was left to die but survived and managed to crawl to a bike path where a passerby found her and called 911, according to investigators.
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Last month, Anissa pleaded guilty to attempted second-degree intentional homicide in the stabbing. She is standing trial to determine whether she is criminally responsible.
The jury, which only requires 10 out of 12 to agree on a ruling either way, will be sequestered throughout the duration of the trial. There are four alternates.
Anissa and Morgan were both charged with attempted first-degree intentional homicide and initially pleaded not guilty by reason of mental illness or defect.
Morgan’s trial is scheduled to begin on Oct. 16. Her attorney told WISN they are hoping to negotiate a similar plea with prosecutors as was reached with Anissa.
A spokesman for Payton’s family told PEOPLE earlier this year that she is “a strong young woman who is excelling in school and doing many things that a teenager would do with her family and friends.”