A Wisconsin judge is set to make a key decision this week regarding the two 13-year-old girls charged with stabbing a classmate to please online horror character Slender Man.

Waukesha County Circuit Judge Michael Bohren will rule Monday whether to move the girls out of adult court and into the juvenile system.

If the girls remain in the adult system and are convicted, they would each face up to 65 years in prison. In the juvenile system, they could be held only for five years.

Defense attorneys argue both girls would receive better mental health treatment in the juvenile system.

Prosecutors say the two girls stabbed their classmate 19 times to curry favor with Slender Man in May 2014. All three girls were 12 years old at the time.