WAUKESHA, Wis. — Doctors have found that one of the two 12-year-old Wisconsin girls accused of stabbing a classmate to please a fictional online horror character is mentally incompetent to stand trial, attorneys said Wednesday.

Prosecutors immediately requested a hearing to discuss the doctors’ conclusions, one from a psychologist hired by the defense and the other from a state-appointed doctor.

In a sign they might expect the girl to plead insanity, the prosecution additionally asked for an evaluation not only of the girl’s present condition, but also of whether mental disease was present at the time of the crime. Hearings are set for Aug. 1.

The girl, who allegedly told police she stabbed the victim about 17 times, appeared in court separately from her co-defendant.

Prosecutors say the girls plotted to kill their 12-year-old friend to curry favor with the online specter known as Slender Man. They lured her to a park on May 31 and stabbed her 19 times, authorities said.

The child survived and is recovering at home.