One of two girls convicted of stabbing a classmate to please the horror character Slender Man asked the Wisconsin Supreme Court on Friday to rule that the case should have been tried in juvenile court.

Morgan Geyser and Anisa Weier attacked their friend, Payton Leutner, in a Waukesha County park following a sleepover in 2014. Geyser stabbed Leutner 19 times, as Weier encouraged her, leaving the girl to die. All three girls were 12 at the time.

Leutner survived the attack. Geyser pleaded guilty to attempted first-degree intentional homicide in adult court in a deal with prosecutors to avoid prison. She was found not guilty by reason of mental disease or defect. Weier pleaded guilty to attempted second-degree intentional homicide in adult court. She was also found not guilty by reason of mental disease or defect.

Geyser was ordered to spend 40 years in a mental health institution, and Weier was committed to one for 25 years. Geyser’s attorney, Matthew Pinx, argued in his petition to the Wisconsin Supreme Court on Friday that Geyser thought she had to kill Lautner or Slender Man would kill her or kill her family. She was acting in self-defense and should have been charged with attempted second-degree intentional homicide in juvenile court, Pinx argued.

He also maintained that Geyser gave statements to detectives before she was read her rights, and she couldn’t really understand what rights she gave up when she agreed to speak alone with a detective while she was in custody and confessed to the stabbing.

The state Department of Justice is defending Geyser’s conviction. Department spokeswoman Gillian Drummond had no immediate comment. Last month, the 2nd District Court of Appeals rejected  the argument that Geyser’s case was overcharged and belonged in juvenile court.