Attorneys representing Anissa Weier and Morgan Geyser, who are charged as adults with first-degree attempted homicide, said after a brief hearing they want the case transferred out of adult court to juvenile court.
Geyser will undergo a mental competency test at the request of her attorney, a Waukesha County Circuit Court commissioner said.
The attorney, Anthony Cotton, said the results of the evaluation, which must be completed within 15 days, will be sealed.
"Anybody can see when you are representing an 11-year-old that just turned 12 the adult court system may not be the best place for them," Cotton told reporters.
Sam Benedict, a public defender who represents Weier, also said juvenile court would be the best place for the case.
Weier's father left the courthouse visibly shaken with his hand over his mouth and tears in his eyes and did not speak to reporters.
On May 31, after a sleepover with their classmate and friend, Weier and Geyser lured her into the woods and stabbed her 19 times with a kitchen knife, according to a criminal complaint.
The girls told investigators they stabbed their friend, whose identity has not been disclosed, to impress Slenderman, a tall, creepy fictional bogeyman they insisted was real, the complaint said. Weier told a detective she thought she would be able to go live with Slenderman if she killed someone, the complaint added.
The stabbing victim was released from the hospital six days after the attack, her family said in a statement posted on a fundraising website.
Wisconsin law requires attempted homicide cases that involve suspects at least 10 years old to begin in adult court before attorneys can ask to have the case moved to juvenile court, away from the media and public.
The court must determine if there is probable cause to proceed with the case before deciding whether it should be heard in juvenile court.
The girls face up to 60 years in prison if convicted as adults of attempted homicide. They could be incarcerated to age 25 if they are convicted as juveniles under Wisconsin law.
A status hearing in the case has been set for July 2.