Attorney for Morgan Geyser says teen should not have been tried as adult in Slender Man case

WAUKESHA, Wis. (CBS 58) -- Morgan Geyser's lawyers filed an appeal in the Slender Man stabbing case. 

Geyser's attorney claims she should not have been tried as an adult because the state proved she did not act out of self-defense when she stabbed a classmate back in 2014. 

He also claims Morgan's interviews with police should be invalid because she was not in the right state of mind during the interview. 

"You can't use a statement that people give to police if they don't understand that they have the right to remain silent or the right to ask for an attorney...and you can't just tell them those things, that's not enough," said Matthew Pinix, Geyser's attorney. 

Geyser was sentenced to 40 years in a mental institution last year. Her co-defendant Anissa Weier was sentenced to 25 years.