A Wisconsin judge is expected to rule Monday whether two 13-year-old girls accused of stabbing a classmate to please online horror character Slender Man will remain in adult court or be moved into the juvenile system. If the girls are to stay in the adult system and are convicted, they could each face as much as 65 years in prison, whereas in the juvenile system, they could be held for just five years, the Associated Press reported Sunday.

"It's obviously a very tough decision for him," said former Wisconsin Supreme Court Justice Janine Geske. "They're very young. They clearly have some serious mental health issues. That pushes you toward putting them in juvenile court. ... But the crime is so severe."

Defense attorneys have argued both girls, 12 at the time they stabbed their classmate, would receive better mental health treatment in the juvenile system. Prosecutors have emphasized the sheer brutality of the crime, noting the girls stabbed their classmate 19 times.

The case has been taken up by advocates for juvenile justice reform, who say they are better fit for the juvenile system given their age. "Anything else is a legal fiction," Kim Dvorchack, director of the National Juvenile Defender Center in Washington, told the Milwaukee-Wisconsin Journal Sentinel

By Wisconsin law, children as young as 10 must be charged as adults for committing serious crimes. The lawyers for both girls are hoping to see them be placed in the juvenile system.

The two girls are accused of luring a classmate into the woods following a sleepover at one of the girls' homes May 31, 2014, for a birthday party. A passing bicyclist found the young girl in a park in a Milwaukee suburb with 19 stab wounds. She suffered serious internal injuries but recovered in time to start the seventh grade, the Milwaukee newspaper reported. 

Both girls were arrested the following day. They told police they hoped to impress the cartoon character Slender Man, in an attempt to prevent the fictional character from killing them or their families if they didn't kill their friend. They reportedly sought to join the character in his mansion.

The two girls were declared competent to stand trial late last year. One of the girls was diagnosed with schizophrenia during a court-ordered competency test.