WAUKESHA, Wis. >> A Wisconsin judge ruled Monday that two girls accused of stabbing a classmate to please the online horror character Slender Man will stay in adult court, where they could face decades in prison.

The 13-year-old girls’ attorneys had sought to transfer their cases to the juvenile court system, where they could be held for only five years. Psychologists called by defense lawyers testified that they would get more suitable mental health treatment in a juvenile institution.

But Waukesha County Circuit Judge Michael Bohren, after hearing testimony during four days of hearings in May and June, decided that the girls should remain in adult court.

Both girls were charged with attempted first-degree intentional homicide in connection with the May 2014 attack on their classmate, Payton Leutner.

According to a criminal complaint, the girls plotted for months before they lured Payton into some woods after a sleepover and attacked her with a knife. Payton was stabbed 19 times but survived.

The girls told investigators they hoped killing Payton would please Slender Man, a character they had read about in online horror stories. All three girls were 12 years old at the time of the attack.

The charges automatically put the girls in adult court under Wisconsin law. They could face 65 years in prison if they’re convicted as adults.

The girls’ defense attorneys also had asked the judge to declare the underlying law that put the case in adult court unconstitutional, alleging the statues lead to cruel and unusual punishment. The judge denied that motion on Thursday, writing that juveniles aren’t as culpable for their actions as adults but that doesn’t exempt them from getting adult sentences.

The Associated Press isn’t naming the defendants because an appeals court could still move their cases to juvenile court, where proceedings are closed to the public.