The doctors' reports have not been made public, but the Morgan Geyser's defense attorney, Anthony Cotton, said a doctor for the state of Wisconsin and a doctor hired by her defense agree that she is not mentally competent.
The results were discussed during a brief court hearing in which prosecutors asked for an additional test for mental disease or defect and a hearing on the mental competency issue. The judge agreed.
Authorities say Geyser and Anissa Weier plotted for months to kill their friend to curry favor with Slender Man, a character in horror stories they read online. They told investigators they believed Slender Man had a mansion in a Wisconsin forest and they planned to go live with him after the slaying.
The two girls attacked the 12-year-old victim in a wooded Waukesha park on May 31 after a sleepover the night before, a criminal complaint says.
Doctors later told police the victim had been stabbed 19 times and the knife missed a major artery near her heart by a millimeter. The child has since been released from a hospital and is recovering at home.
Wisconsin law requires attempted homicide cases to start in adult court if a suspect is at least 10, but the girls' attorneys have said they hope to see the charges moved to juvenile court, where more services might be available.
Court proceedings typically halt once a defendant is found incompetent to allow time for treatment. However, Cotton had filed a motion Monday asking the judge to allow pretrial proceedings in his client's case to continue even if she is found incompetent.
One thing that could be addressed while she is in a hospital is a yet-to-be-filed request to move her case to juvenile court, Cotton said.