Teddy is an innocent man.
What is he guilty of exactly? As Gleamy-Jog has pointed out in his posts, being in an institute for the criminally insane, then he would be not guilty by reason of insanity. Teddy is not a threat to society, and a strong case would be made that he performed a mercy killing on his wife, or even for self-defense.
The only real monster is Doctor Cawley, who uses the barbaric technique of lobotomizing his patients instead of helping them.
~ I'm a 21st century man and I don't wanna be here.