One of the girls accused of stabbing a classmate after developing an obsession with a horror character has been found "mentally incapable" to stand trial by doctors.

On Wednesday, Judge Michael Bohren ordered a competency hearing for one of the girls accused of luring a classmate into the woods and stabbing her 19 times, after two experts argued that she was not mentally capable to stand trial.

The hearing on her mental competency is set to take place next month and will determine whether the 12-year is mentally fit and understands the charges before launching her defence.

Download the new Independent Premium app Sharing the full story, not just the headlines

"This is all part of the process, looking at the mental health, looking at her functioning competency and issues like that," her lawyer, Anthony Cotton, said.

The two girls were charged in June as adults with first-degree attempted homicide after they allegedly attacked a classmate to please the so-called 'Slender Man'. The two girls appeared in court today in handcuffs.

According to investigators, the girls had developed a fascination with the ‘Slender Man’, a fictional horror character, and plotted the attack on the girl to demonstrate their loyalty to the mythical creature. The victim has since been released from hospital and is now recovering at home.

The Slender Man is often featured in blogs and online forums dedicated to horror stories such as Creepypasta Wiki and Reddit's No Sleep. According to the myth, he hypnotises his victims, mostly children, and his followers must show their dedication by killing.