Attorney: Slender Man Stabber's Confession Should Not Have Been Allowed in Trial

Her appeal challenges whether she really had the ability to waive her rights against incriminating herself.

"When she said she would give a statement waiving her rights, she didn't have any comprehension of what those rights were," Geyser's attorney, Matthew Pinx, said.

This week, the appeal gained some allies, with the Philadelphia-based Juvenile Law Center among those filing a supporting brief.

"We are deeply concerned that this was simply not a lawful or constitutional waiver of her rights," said Marsha Levick of the Juvenile Law Center.